Mars is the fourth
planetA planet , is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
from the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
in the
Solar SystemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
. The planet is named after
MarsMars was the Roman god of war, the son of Juno and Jupiter, husband of Bellona, and the lover of Venus. He was the most prominent of the military gods that were worshipped by the Roman legions. The martial Romans considered him second in importance only to Jupiter...
, the
RomanRoman mythology, or Latin mythology, refers to the mythological beliefs of the Italic people inhabiting the region of Latium and its main city, Ancient Rome. It can be considered as having two parts; One part, largely later and literary, consists of borrowings from Greek mythology...
god of war. It is also referred to as the "
Red PlanetRed Planet is a nickname for the planet Mars, due to its surface color. It may also refer to:* Red Planet by Robert A. Heinlein* Red Planet , an 1994 animated adaptation of the novel...
" because of its
reddish appearanceThe apparent color of the Martian surface enabled humans to distinguish it from other planets early in human history and motivated them to weave fables of war in association with Mars. One of its earliest names, Har decher, literally meant "Red One" in Egyptian...
, due to
iron oxideIron oxide—also known as ferric oxide, ferric iron, hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust—is one of the several oxide compounds of iron, and has paramagnetic properties...
prevalent on its surface.
Mars is a
terrestrial planetA terrestrial planet, telluric planet, rocky planet or inner planet is a planet that is primarily composed of silicate rocks. Within the solar system, the terrestrial planets are the closest planets to the Sun...
with a thin
atmosphereAn atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low...
, having surface features reminiscent both of the
impact craterIn the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
s of the
MoonThe Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is , about thirty times the diameter of the Earth. The common centre of mass of the system is located at about —a quarter the Earth's...
and the
volcano3. Conduit
4. Base
5. Sill
6. Dike
7. Layers of ash emitted by the volcano
8. Flank| 9. Layers of lava emitted by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14. Crater
15...
es,
valleyIn geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
s,
desertA desert is a landscape or region that receives almost no precipitation. Deserts are defined as areas with an average annual precipitation of less than per year, or as areas where more water is lost by evapotranspiration than falls as precipitation. In the Köppen climate classification system,...
s and polar ice caps of
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
. It is the site of
Olympus MonsOlympus Mons is the tallest known volcano and mountain in the Solar System and was formed during the Amazonian epoch. It is located on the planet Mars at approximately 18°N 133°W / 18, -133. It is three times as tall as Mount Everest...
, the highest known
mountainA mountain is a large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. The adjective montane is used to describe mountainous areas and things associated with them...
in the Solar System, and of
Valles MarinerisValles Marineris is system that runs along the Martian east of the Tharsis region...
, the largest canyon. Furthermore, in June 2008 three articles published in
NatureNature is a prominent British scientific journal, first published on 4 November 1869. Most scientific journals are now highly specialized, and Nature is among the few journals that still publish original research articles across a wide range of scientific...
presented evidence of an enormous impact crater in Mars's northern hemisphere, 10,600 km long by 8,500 km wide, or roughly four times larger than the largest impact crater yet discovered, the
South Pole-Aitken basinThe South Pole-Aitken basin is an impact crater on Earth's Moon. Roughly 2500 kilometers in diameter and 13 kilometers deep, it is the second largest known impact crater in the entire Solar System, the largest being the one on Mars' northern hemisphere which is approximately four times as big. An...
. In addition to its geographical features, Mars’ rotational period and
seasonA season is a division of the year, marked by changes in weather.Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution...
al cycles are likewise similar to those of Earth.
Until the first flyby of Mars by
Mariner 4Mariner 4 was the fourth in a series of spacecraft, launched on November 28, 1964, intended for planetary exploration in a flyby mode and performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface...
in 1965, many speculated that there might be liquid water on the planet's surface. This was based on observations of periodic variations in
lightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
and
darkDarkness is the absence of light. Scientifically it is only possible to have a reduced amount of light. The emotional response to an absence of light has inspired metaphor in literature, symbolism in art, and emphasis....
patches, particularly in the polar
latitudeLatitude, usually denoted by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the imaginary horizontal lines shown running east-to-west on maps that run either north or south of the equator...
s, which looked like seas and continents, while long, dark striations were interpreted by some observers as irrigation channels for liquid water. These straight line features were later proven not to exist and were instead explained as
optical illusionAn optical illusion is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source...
s. Still, of all the planets in the Solar System other than Earth, Mars is the most likely to harbor liquid water, and perhaps
lifeLife is a characteristic that distinguishes objects that have self-sustaining biological processes from those that do not—either because such functions have ceased , or else because they lack such functions and are classified as "inanimate."In biology, the science of living organisms, "life"...
. Radar data from
Mars ExpressMars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...
and the
Mars Reconnaissance OrbiterNASA's Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit....
have revealed the presence of large quantities of water ice both at the poles (July 2005) and at mid-latitudes (November 2008). The Phoenix Mars Lander directly sampled water ice in shallow martian soil on July 31, 2008.
Mars is currently host to three functional orbiting
spacecraftA spacecraft is a craft or machine designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as...
:
Mars Odyssey,
Mars ExpressMars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...
, and the
Mars Reconnaissance OrbiterNASA's Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit....
. With the exception of Earth, this is more than any planet in the Solar System. The surface is also home to the two
Mars Exploration RoverNASA's Mars Exploration Rover Mission is an ongoing robotic mission of exploring Mars, that began in 2003 with the sending of two rovers — MER-A Spirit and MER-B Opportunity — to explore the Martian surface and geology....
s (
SpiritSpirit, mission designation MER-A , is the first of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully on Mars on 04:35 Ground UTC on January 4, 2004, three weeks before its twin Opportunity landed on the other side of the planet...
and
OpportunityOpportunity, mission designation MER-B , is the second of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully at Meridiani Planum on Mars on January 25, 2004 05:05 Ground UTC , three weeks after its twin Spirit had landed on the other side of the planet...
) and several inert landers and rovers, both successful and unsuccessful. The
PhoenixPhoenix was a robotic spacecraft on a space exploration mission on Mars under the Mars Scout Program. The Phoenix lander descended on Mars on May 25, 2008...
landerA lander is a spacecraft which descends toward and comes to rest on the surface of an astronomical body. For bodies with atmospheres, the landing is called atmospheric reentry and the lander descends as a re-entry vehicle...
recently completed its mission on the surface. Geological evidence gathered by these and preceding missions suggests that Mars previously had large-scale water coverage, while observations also indicate that small
geyserA geyser is a hot spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase . The name geyser comes from Geysir, the name of an erupting spring at Haukadalur, Iceland; that name, in turn, comes from the Icelandic verb gjósa, "to gush".The...
-like water flows have occurred during the past decade.
Observations by
NASAThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
's
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
show evidence that parts of the southern polar ice cap have been receding.
Mars has two
moonsA natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify...
,
PhobosPhobos is the larger and closer of two small moons of Mars, the other being Deimos. It is named after the Greek god Phobos , a son of Ares...
and
DeimosDeimos , is the smaller and outer of Mars’ two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:...
, which are small and irregularly shaped. These may be captured
asteroidthumb|260px|right|[[253 Mathilde]], a [[C-type asteroid]] measuring about across. Photograph taken in 1997 by the [[NEAR Shoemaker]] probe.Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are...
s, similar to
5261 Eureka5261 Eureka was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Lagrangian asteroid. It trails Mars at a distance varying by only 0.3 AU during each revolution...
, a Martian
Trojan asteroidThe Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of the planet's two Lagrangian points of stability, and , that respectively lie 60° ahead...
. Mars can be seen from Earth with the naked eye. Its
apparent magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere...
reaches −2.9, a brightness surpassed only by
VenusVenus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6...
, the Moon, and the Sun, although most of the time
JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with a mass slightly less than one-thousandth that of the Sun but is two and a half times the mass of all of the other planets in our Solar System combined. Jupiter is classified as a gas...
will appear brighter to the naked eye than Mars. Mars has an average opposition distance of 78 million km but can come as close as 55.7 million km during a close approach, such as occurred in 2003.
Physical characteristics
Mars has approximately half the
radiusIn classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter....
of Earth. It is less dense than Earth, having about 15% of Earth's volume and 11% of the
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
. Its
surface areaSurface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved then the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...
is only slightly less than the total area of Earth's dry land. While Mars is larger and more massive than
MercuryFor the liquid metallic element, see Mercury .Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three...
, Mercury has a higher density. This results in a slightly stronger gravitational force at Mercury's surface. Mars is also roughly intermediate in size, mass, and
surface gravityThe surface gravity, g, of an astronomical or other object is the gravitational acceleration experienced at its surface. The surface gravity may be thought of as the acceleration due to gravity experienced by a hypothetical test particle which is very close to the object's surface and which, in...
between Earth and Earth's Moon (the Moon is about half the diameter of Mars, whereas Earth is twice; the Earth is about ten times more massive than Mars, and the Moon ten times
less massive). The red-orange appearance of the Martian surface is caused by
iron(III) oxideIron oxide—also known as ferric oxide, ferric iron, hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust—is one of the several oxide compounds of iron, and has paramagnetic properties...
, more commonly known as hematite, or rust.
Geology
Based on orbital observations and the examination of the Martian meteorite collection, the surface of Mars appears to be composed primarily of
basaltBasalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey.On Earth, most...
. Some evidence suggests that a portion of the Martian surface is more silica-rich than typical basalt, and may be similar to andesitic rocks on Earth; however, these observations may also be explained by silica glass. Much of the surface is deeply covered by finely grained
iron(III) oxideIron oxide—also known as ferric oxide, ferric iron, hematite, red iron oxide, synthetic maghemite, colcothar, or simply rust—is one of the several oxide compounds of iron, and has paramagnetic properties...
dust.
Although Mars has no evidence of structured global
magnetic fieldMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges...
, observations show that parts of the planet's crust have been magnetized and that alternating polarity reversals of its dipole field have occurred. This
paleomagnetismPaleomagnetism is the study of the record of the Earth's magnetic field preserved in various magnetic minerals through time. The study of paleomagnetism has demonstrated that the Earth's magnetic field varies substantially in both orientation and intensity through time.A paleomagnetist is a...
of magnetically susceptible minerals has properties that are very similar to the alternating bands found on the ocean floors of Earth. One theory, published in 1999 and re-examined in October 2005 (with the help of the
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
), is that these bands demonstrate
plate tectonicsPlate tectonics is a theory which describes the large scale motions of Earth's lithosphere...
on Mars 4
billion1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 10
9....
years ago, before the planetary
dynamoThe dynamo theory proposes a mechanism by which a celestial body such as the Earth generates a magnetic field.-History of theory:In 1905, shortly after composing his special relativity paper, Albert Einstein described the origin of the Earth's magnetic field as being one of the great unsolved...
ceased to function and caused the planet's magnetic field to fade away.
Current models of the planet's interior imply a core region about 1,480 kilometres in radius, consisting primarily of
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
with about 14–17%
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
. This
iron sulfideIron sulfide or Iron sulphide may refer to a chemical compound of iron and sulfur with a formula*FeS*FeS2...
core is partially fluid, and has twice the concentration of the lighter elements than exist at Earth's core. The core is surrounded by a silicate
mantleThe mantle is a part of an astronomical object. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core. Earth's mantle is about 2,970 km thick rocky shell that...
that formed many of the tectonic and volcanic features on the planet, but now appears to be inactive. The average thickness of the planet's crust is about 50 km, with a maximum thickness of 125 km. Earth's crust, averaging 40 km, is only a third as thick as Mars’ crust relative to the sizes of the two planets.
The geological history of Mars can be split into many epochs, but the following are the three main ones:
- Noachian epoch (named after Noachis Terra
Noachis Terra is an extensive southern landmass of the planet Mars. It lies roughly between the latitudes −20° and −80° and longitudes 30° west and 30° east, centered on The term "Noachian epoch" is derived from this region....
): Formation of the oldest extant surfaces of Mars, 3.8 billion years ago to 3.5 billion years ago. Noachian age surfaces are scarred by many large impact craters. The TharsisThe Tharsis region on Mars is an enormous volcanic plateau located on Mars' equator, at the western end of Valles Marineris. Its name comes from the Bible, where it was the name for the land at western extremity of the known world....
bulge volcanic upland is thought to have formed during this period, with extensive flooding by liquid water late in the epoch.
- Hesperian epoch (named after Hesperia Planum): 3.5 billion years ago to 1.8 billion years ago. The Hesperian epoch is marked by the formation of extensive lava plains.
- Amazonian epoch (named after Amazonis Planitia
Amazonis Planitia is one of the smoothest plains on Mars. It is located between the Tharsis and Elysium volcanic provinces to the west of Olympus Mons in the Valles Marineris region of the Memnonia quadrangle, centered at . Its topography exhibits extremely smooth features at several different...
): 1.8 billion years ago to present. Amazonian regions have few meteorite impactAn impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Impact events have been a plot and background element in science fiction since knowledge of real impacts became established in the scientific mainstream.-Sizes and...
craters but are otherwise quite varied. Olympus MonsOlympus Mons is the tallest known volcano and mountain in the Solar System and was formed during the Amazonian epoch. It is located on the planet Mars at approximately 18°N 133°W / 18, -133. It is three times as tall as Mount Everest...
formed during this period along with lava flows elsewhere on Mars.
A major geological event occurred on Mars on February 19, 2008, and was caught on camera by the
Mars Reconnaissance OrbiterNASA's Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit....
. Images capturing a spectacular avalanche of materials thought to be fine grained ice, dust, and large blocks are shown to have detached from a 700-metre high cliff. Evidence of the avalanche is present in the dust clouds left above the cliff afterwards.
Recent studies support a theory, first proposed in the 1980s, that Mars was struck by a
PlutoPluto, formal designation 134340 Pluto, is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun...
-sized body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet.
Soil
In June, 2008, the Phoenix Lander returned data showing Martian soil to be slightly alkaline and containing vital nutrients such as
magnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the earth's crust by mass, although ninth in the Universe as a whole...
,
sodiumSodium is a metallic element with a symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1"...
,
potassiumPotassium is the chemical element with the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash...
and
chlorideThe chloride ion is formed when the element chlorine picks up one electron to form an anion Cl
−...
, all of which are necessary for living organisms to grow. Scientists compared the soil near Mars's north pole to that of backyard gardens on Earth, and concluded that it could be suitable for growth of plants such as
asparagusAsparagus officinalis is a flowering plant species in the genus Asparagus from which the vegetable known as asparagus is obtained. It is native to most of Europe, northern Africa and western Asia...
. However, in August, 2008, the Phoenix Lander conducted simple
chemistryChemistry is the science concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions...
experiments, mixing water from Earth with Martian soil in an attempt to test its
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
, and discovered traces of the salt
perchloratePerchlorates are the salts derived from perchloric acid . They occur both naturally and through manufacturing. They have been used as a medicine for more than 50 years to treat thyroid gland disorders. They are also used as an oxidizer in rocket fuel and explosives and can be found in airbags...
, while also confirming many scientists theories that the Martian surface was considerably basic, measuring at 8.3. The presence of the perchlorate, if confirmed, would make Martian soil more exotic than previously believed. Further testing is necessary to eliminate the possibility of the perchlorate readings being caused by terrestrial sources, which may have migrated from the spacecraft either into samples or the instrumentation.
Hydrology
Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, except at the lowest elevations for short periods but water ice is in no short supply, with two polar ice caps made largely of ice. In March 2007, NASA announced that the volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 metres. Additionally, an ice
permafrostIn geology, permafrost or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground...
mantle stretches down from the pole to latitudes of about 60°.
Large quantities of waterThe evolution of water on either planet needs be understood in the context of the other terrestrial planetary bodies and their current water status.- Water Inventory of Mars:...
are thought to be trapped underneath Mars's thick
cryosphereThe cryosphere, derived from the Greek word cryo for "cold" or "to cold", is the term which collectively describes the portions of the Earth’s surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps and ice sheets, and frozen ground...
. Radar data from
Mars ExpressMars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...
and the
Mars Reconnaissance OrbiterNASA's Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit....
have revealed the presence of large quantities of water ice both at the poles (July 2005) and at mid-latitudes (November 2008). The Phoenix Mars Lander directly sampled water ice in shallow martian soil on July 31, 2008. A large release of liquid water is thought to have occurred when the
Valles MarinerisValles Marineris is system that runs along the Martian east of the Tharsis region...
formed early in Mars's history, forming massive
outflow channelsThe outflow channels of Mars are large channel systems that formed by fluid flow from the sub-surface. The largest outflow channels are thousands of kilometers in length....
. A smaller but more recent outflow may have occurred when the
Cerberus FossaeThe Cerberus Fossae are a series of semi-parallel fissures on Mars formed by faults which pulled the crust apart in the Cerberus region . Ripples seen at the bottom of the fault are sand blown by the wind ....
chasm opened about 5
millionOne million or one thousand thousand, is the natural number following 999,999 and preceding 1,000,001. The name is derived from Italian, where mille was 1,000, and 1,000,000 became milione, "a large thousand"....
years ago, leaving a supposed sea of frozen ice still visible today on the
Elysium PlanitiaElysium Planitia is the second largest volcanic region on Mars, after Tharsis Montes. It includes volcanoes, from north to south, Hecates Tholus, Elysium Mons and Albor Tholus. It is centered at ....
centered at Cerberus Palus. However, the morphology of this region may correspond to the ponding of lava flows, causing a superficial morphology similar to ice flows, which probably draped the terrain established by earlier massive floods of Athabasca Valles. Rough surface texture at decimetre (dm) scales, thermal inertia comparable to that of the Gusev plains, and hydrovolcanic cones are consistent with the lava flow hypothesis. Furthermore, the stoichiometric mass fraction of water in this area to tens of centimetre depths is only ~4%, easily attributable to hydrated minerals and inconsistent with the presence of near-surface ice.
More recently the high resolution Mars Orbiter Camera on the
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
has taken pictures which give much more detail about the history of liquid water on the surface of Mars. Despite the many giant flood channels and associated tree-like network of tributaries found on Mars there are no smaller scale structures that would indicate the origin of the flood waters. It has been suggested that weathering processes have denuded these, indicating the river valleys are old features. Higher resolution observations from spacecraft like Mars Global Surveyor also revealed at least a few hundred features along crater and canyon walls that appear similar to terrestrial seepage
gulliesA gully is a landform created by running water eroding sharply into soil, typically on a hillside. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width...
. The gullies tend to be in the highlands of the southern hemisphere and to face the Equator; all are poleward of 30° latitude. The researchers found no partially degraded (
i.e. weathered) gullies and no superimposed impact craters, indicating that these are very young features.
In a particularly striking example (see image) two photographs, taken six years apart, show a gully on Mars with what appears to be new deposits of sediment. Michael Meyer, the lead scientist for NASA's Mars Exploration Program, argues that only the flow of material with a high liquid water content could produce such a debris pattern and colouring. Whether the water results from precipitation, underground or another source remains an open question.
However, alternative scenarios have been suggested, including the possibility of the deposits being caused by carbon dioxide frost or by the movement of dust on the Martian surface.
Further evidence that
liquidLiquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container....
water once existed on the surface of Mars comes from the detection of specific minerals such as
hematiteHematite, also spelled as hæmatite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...
and
goethiteGoethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
, both of which sometimes form in the presence of water.
Nevertheless, some of the evidence believed to indicate ancient water basins and flows has been negated by higher resolution studies taken at resolution about 30 cm by the Mars Reconnaissance Orbiter.
Geysers on Mars
The seasonal frosting and defrosting of the southern ice cap results in the formation of spider-like radial channels carved on 1 meter thick ice by sunlight. Then, sublimed CO
2 -and probably water- increase pressure in their interior producing geyser-like eruptions of cold fluids often mixed with dark basaltic sand or mud. This process is rapid, observed happening in the space of a few days, weeks or months, a growth rate rather unusual in geology — especially for Mars.
Dark Slope Streaks
The inset photo of
Tharsis TholusTharsis Tholus is a Martian intermediate sized shield volcano which measures 155 km x 126 km. It is up to 9 km high at the west flank and located at 13.5°N, 91°W on the margin of the Tharsis area....
shows an example of a dark streak. Such streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. Sometimes the streaks start in a tiny area which then spreads out for hundreds of metres. They have also been seen to travel around boulders and other obstacles in their path. The mainstream theory is that they are dark underlying layers of soil revealed after avalanches of bright dust, however several ideas have been put forward to explain them, some of which involve
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
or even the growth of organisms.
Geography
Although better remembered for mapping the Moon, Johann Heinrich Mädler and
Wilhelm BeerWilhelm Wolff Beer was a banker and astronomer from Berlin, Prussia, and the brother of Giacomo Meyerbeer.- Astronomy :...
were the first "areographers". They began by establishing once and for all that most of Mars’ surface features were permanent, and determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. Rather than giving names to the various markings, Beer and Mädler simply designated them with letters; Meridian Bay (Sinus Meridiani) was thus feature "
a."
Today, features on Mars are named from a number of sources. Large
albedoThe albedo of an object is the extent to which it diffusely reflects light from light sources such as the Sun. It is therefore a more specific form of the term reflectivity. Albedo is defined as the ratio of diffusely reflected to incident electromagnetic radiation. It is a unitless measure...
features retain many of the older names, but are often updated to reflect new knowledge of the nature of the features. For example,
Nix Olympica (the snows of Olympus) has become
Olympus Mons (Mount Olympus).
Mars’ equator is defined by its rotation, but the location of its
Prime MeridianThe Prime Meridian is the meridian at which longitude is defined to be 0°.The Prime Meridian and its opposite the 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.Unlike the parallels of...
was specified, as was Earth's (at
GreenwichGreenwich is a district in south-east London, England, on the south bank of the River Thames in the London Borough of Greenwich. It is best known for its maritime history and as giving its name to the Greenwich Meridian and Greenwich Mean Time.The town became the site of a Royal palace, the...
), by choice of an arbitrary point; Mädler and Beer selected a line in 1830 for their first maps of Mars. After the spacecraft
Mariner 9Mariner 9 was a NASA space probe orbiter that helped in the exploration of Mars and was part of the Mariner program...
provided extensive imagery of Mars in 1972, a small crater (later called
Airy-0Airy-0 is a crater on Mars whose location defines the position of the prime meridian of that planet. Airy-0 is about 0.5 kilometers across and lies within the larger crater Airy in the region Sinus Meridiani....
), located in the
Sinus MeridianiSinus Meridiani is a feature name for an albedo feature on Mars stretching east-west just south of that planet's equator. It was named by the French astronomer Camille Flammarion in the late 1870s.-Observational History:...
("Middle Bay" or "Meridian Bay"), was chosen for the definition of 0.0° longitude to coincide with the original selection.
Since Mars has no oceans and hence no 'sea level', a zero-elevation surface or mean gravity surface also had to be selected. Zero altitude is defined by the height at which there is 610.5
PaThe pascal is the SI derived unit of pressure, stress, Young's modulus and tensile strength. It is a measure of force per unit area, defined as one newton per square metre...
(6.105 mbar) of atmospheric pressure. This pressure corresponds to the
triple pointIn thermodynamics, the triple point of a substance is the temperature and pressure at which three phases of that substance coexist in thermodynamic equilibrium...
of water, and is about 0.6% of the sea level surface pressure on Earth (.006 atm).
The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. Research in 2008 has presented evidence regarding a theory proposed in 1980 postulating that, four billion years ago, the northern hemisphere of Mars was struck by an object one-tenth to two-thirds the size of the Moon. If validated, this would make Mars's northern hemisphere the site of an impact crater 10,600 km long by 8,500 km wide, or roughly the area of Europe, Asia, and Australia combined, surpassing the
South Pole-Aitken basinThe South Pole-Aitken basin is an impact crater on Earth's Moon. Roughly 2500 kilometers in diameter and 13 kilometers deep, it is the second largest known impact crater in the entire Solar System, the largest being the one on Mars' northern hemisphere which is approximately four times as big. An...
as the largest impact crater in the Solar System. The surface of Mars as seen from Earth is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian 'continents' and given names like
Arabia TerraArabia Terra is a large upland region in the north of Mars in that lies mostly in the Arabia quadrangle. It is densely cratered and heavily eroded. This battered topography indicates great age, and Arabia Terra is presumed to be one of the oldest terrains on the planet...
(
land of Arabia) or
Amazonis PlanitiaAmazonis Planitia is one of the smoothest plains on Mars. It is located between the Tharsis and Elysium volcanic provinces to the west of Olympus Mons in the Valles Marineris region of the Memnonia quadrangle, centered at . Its topography exhibits extremely smooth features at several different...
(
Amazonian plain). The dark features were thought to be seas, hence their names
Mare ErythraeumMare Erythraeum is a very large dark dusky region of Mars that can be viewed by even a small telescope. The name comes from the Latin for the Arabian Sea, because it was originally thought to be a large sea of liquid water. It was included in Percival Lowell's 1895 map of Mars.-External links:*...
, Mare Sirenum and
Aurorae SinusAurorae Sinus is a dark feature in the southern hemisphere of the planet Mars. Together with albedo features contributed by Aonius Sinus and Solis Lacus, it is part of a feature known as the "eye of Mars"....
. The largest dark feature seen from Earth is
Syrtis MajorSyrtis Major Planum is a "dark spot" located in the boundary between the northern lowlands and southern highlands of Mars. It was discovered, on the basis of data from Mars Global Surveyor, to be a low-relief shield volcano, but was formerly believed to be a plain, and was then known as Syrtis...
.
The
shield volcanoA shield volcano is a large volcano with shallow-sloping sides. Shield volcanoes are formed from fluid lava that can travel long distances across slight inclines, resulting in their relatively flat, broad profile...
,
Olympus MonsOlympus Mons is the tallest known volcano and mountain in the Solar System and was formed during the Amazonian epoch. It is located on the planet Mars at approximately 18°N 133°W / 18, -133. It is three times as tall as Mount Everest...
(
Mount Olympus), at 26 km is the highest known mountain in the Solar System. It is an extinct volcano in the vast upland region
TharsisThe Tharsis region on Mars is an enormous volcanic plateau located on Mars' equator, at the western end of Valles Marineris. Its name comes from the Bible, where it was the name for the land at western extremity of the known world....
, which contains several other large volcanoes. Olympus Mons is over three times the height of
Mount EverestMount Everest – also called Sagarmāthā , Chomolungma or Qomolangma or Zhumulangma – is the highest mountain on Earth, and the highest point on the Earth's crust, as measured by the height above sea level of its summit,...
, which in comparison stands at just over 8.8 km.
Mars is also scarred by a number of
impact craterIn the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
s: a total of 43,000 craters with a diameter of 5 km or greater have been found. The largest confirmed of these is the
Hellas impact basinHellas Planitia, also known as the Hellas Impact Basin, is a huge, roughly circular impact basin located in the southern hemisphere of the planet Mars. It is the second or third largest impact crater and the largest visible impact crater known in the Solar System. The basin floor is 3 km deeper...
, a light
albedo featureAn albedo feature is a large area on the surface of a planet which shows a contrast in brightness or darkness with adjacent areas....
clearly visible from Earth. Due to the smaller mass of Mars, the probability of an object colliding with the planet is about half that of the Earth. However, Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is also more likely to be struck by short-period
cometA comet is a Small Solar System Body that has coma and is bigger than a meteoroid. When close enough to the Sun, a comet exhibits a visible coma , and sometimes a tail, both because of the effects of solar radiation upon the comet's nucleus...
s,
i.e., those that lie within the orbit of Jupiter. In spite of this, there are far fewer craters on Mars compared with
the MoonThe Moon is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is , about thirty times the diameter of the Earth. The common centre of mass of the system is located at about —a quarter the Earth's...
because Mars's atmosphere provides protection against small meteors. Some craters have a morphology that suggests the ground was wet when the meteor impacted.
The large canyon,
Valles MarinerisValles Marineris is system that runs along the Martian east of the Tharsis region...
(Latin for
MarinerThe Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury...
Valleys, also known as Agathadaemon in the old canal maps), has a length of 4,000 km and a depth of up to 7 km. The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the
Grand CanyonThe Grand Canyon is a steep-sided gorge carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, one of the first national parks in the United States...
on Earth is only 446 km long and nearly 2 km deep. Valles Marineris was formed due to the swelling of the Tharsis area which caused the crust in the area of Valles Marineris to collapse. Another large canyon is
Ma'adim VallisMa'adim Vallis is one of the largest canyons on Mars, about 700 km long and significantly larger than Earth's Grand Canyon. It is over 20 km wide and 2 km deep in some places. It runs from a region of southern lowlands thought to have once contained a large group of lakes north to...
(
Ma'adim is Hebrew for Mars). It is 700 km long and again much bigger than the Grand Canyon with a width of 20 km and a depth of 2 km in some places. It is possible that Ma'adim Vallis was flooded with liquid water in the past.
Images from the
Thermal Emission Imaging SystemThe Thermal Emission Imaging System is a camera on board the 2001 Mars Odyssey orbiter. It images Mars in the visible and infrared parts of the electromagnetic spectrum in order to determine the thermal properties of the surface and to refine the distribution of minerals on the surface of Mars as...
(THEMIS) aboard NASA's
Mars Odyssey orbiter2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. Its mission is to use spectrometers and imagers to hunt for evidence of past or present water and volcanic activity on Mars. It is hoped that the data Odyssey obtains will help answer the question of whether life has ever existed...
have revealed seven possible
caveA cave or cavern is a natural underground void large enough for a human to enter. Some people suggest that the term cave should only apply to cavities that have some part that does not receive daylight; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and...
entrances on the flanks of the
Arsia MonsArsia Mons is the southernmost of three volcanos on the Tharsis bulge near the equator of the planet Mars. To its north is Pavonis Mons, and north of that is Ascraeus Mons. The tallest mountain in the solar system, Olympus Mons, is to its northwest...
volcano. The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters." Cave entrances measure from 100 m to 252 m wide and they are believed to be at least 73 m to 96 m deep. Because light does not reach the floor of most of the caves, it is likely that they extend much deeper than these lower estimates and widen below the surface. "Dena" is the only exception; its floor is visible and was measured to be 130 m deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation,
solar flareA solar flare is a large explosion in the Sun's atmosphere that can release as much as 6 × 10
25 joules of energy. The term is also used to refer to similar phenomena in other stars, where the more accurate term stellar flare applies....
s and high energy particles that bombard the planet's surface. Some researchers have suggested that this protection makes the caves good candidates for future efforts to find liquid water and signs of life.
Mars has two permanent polar ice caps: the northern one at
Planum BoreumPlanum Boreum is the northern polar plain on Mars. It extends northward from roughly 80°N and is centered at . Surrounding the high polar plain is a flat and featureless lowland plain called Vastitas Borealis which extends for approximately 1500 kilometres southwards, dominating the northern...
and the southern one at
Planum AustralePlanum Australe is the southern polar plain on Mars. It extends southward of roughly 75°S and is centered at . The geology of this region was to be explored by the failed NASA mission Mars Polar Lander, which lost contact on entry into the Martian atmosphere.-Ice cap:Planum Australe is partially...
.
Atmosphere
Mars lost its
magnetosphereA magnetosphere is a highly magnetized region around and possessed by an astronomical object. Earth is surrounded by a magnetosphere, as are the magnetized planets Mercury, Jupiter, Saturn, Uranus, and Neptune. Jupiter's moon Ganymede is magnetized, but too weak to trap solar wind plasma. Mars has...
4 billion years ago, so the
solar windThe solar wind is a stream of charged particles ejected from the upper atmosphere of the sun. It consists mostly of electrons and protons with energies of about 1 keV. The stream of particles varies in temperature and speed with the passage of time...
interacts directly with the Martian
ionosphereThe ionosphere is the uppermost part of the atmosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer. Both
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
and Mars Express have detected these ionised atmospheric particles trailing off into space behind Mars.
The atmosphere of Mars is now relatively thin.
Atmospheric pressureAtmospheric pressure is defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above...
on the surface varies from around 30
PaThe pascal is the SI derived unit of pressure, stress, Young's modulus and tensile strength. It is a measure of force per unit area, defined as one newton per square metre...
(0.03 kPa) on
Olympus MonsOlympus Mons is the tallest known volcano and mountain in the Solar System and was formed during the Amazonian epoch. It is located on the planet Mars at approximately 18°N 133°W / 18, -133. It is three times as tall as Mount Everest...
to over 1,155 Pa (1.155 kPa) in the depths of
Hellas PlanitiaHellas Planitia, also known as the Hellas Impact Basin, is a huge, roughly circular impact basin located in the southern hemisphere of the planet Mars. It is the second or third largest impact crater and the largest visible impact crater known in the Solar System. The basin floor is 3 km deeper...
, with a mean surface level pressure of 600 Pa (0.6 kPa). Mars's mean surface pressure equals the pressure found 35 km above the Earth's surface. This is less than 1% of the surface pressure on Earth (101.3 kPa). The
scale heightA scale height is a term often used in scientific contexts for a distance over which a quantity decreases by a factor of e...
of the atmosphere, about 11 km, is higher than Earth's (6 km) due to the lower gravity. Mars' gravity is only about 38% of the surface gravity on Earth.
The atmosphere on Mars consists of 95%
carbon dioxideCarbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
, 3%
nitrogenNitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
, 1.6%
argonArgon is a chemical element designated by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is present in the Earth's atmosphere at 0.94%. Terrestrially, it is the most abundant and most frequently used of the noble gases...
, and contains traces of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
and water. The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a
tawnyTawny is a pale orange-brown, or yellow-brown colour, close to fulvous. Tawny is often used as a feminine given or assumed name. In heraldry, it is usually called tenné.Notable people with the name include:* Tawny Cypress , American actress...
color when seen from the surface.
Several researchers claim to have detected
methaneMethane is a chemical compound with the chemical formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane and its clean...
in the Martian atmosphere with a concentration of about 30 ppb by volume.
Since methane is an unstable
gasThis page is about the physical properties of gas as a state of matter. For the uses of gases, and other meanings, see Gas .A gas is one of four states of matter. Near absolute zero, a substance exists as a solid...
that is broken down by
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation, typically lasting about 340 years in the Martian atmosphere, its presence would indicate a current or recent source of the gas on the planet. Volcanic activity,
cometA comet is a Small Solar System Body that has coma and is bigger than a meteoroid. When close enough to the Sun, a comet exhibits a visible coma , and sometimes a tail, both because of the effects of solar radiation upon the comet's nucleus...
ary impacts, and the presence of
methanogenMethanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They were once classified as archaebacteria but archaebacteria have now been reclasified as archaea a group quite distinct from bacteria...
ic
microbialA microorganism or microbe is an organism that is microscopic...
life forms are among possible sources. It was recently pointed out that methane could also be produced by a non-biological process called
serpentinizationSerpentinite is a rock composed of one or more serpentine minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle. The alteration is particularly important at the sea floor at tectonic plate boundaries...
involving water, carbon dioxide, and the
mineralA mineral is a naturally occurring solid formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock, by comparison, is an aggregate of minerals and/or mineraloids, and need not have a specific...
olivineThe mineral olivine is a magnesium iron silicate with the formula
2SiO
4...
, which is known to be common on Mars.
During a pole's winter, it lies in continuous darkness, chilling the surface and causing 25–30% of the atmosphere to condense out into thick slabs of
CO2Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state...
ice (
dry iceDry ice, sometimes referred to as "Cardice" or as "card ice" is the solid form of carbon dioxide. It is commonly used as a versatile cooling agent.- Properties :...
). When the poles are again exposed to sunlight, the frozen CO
2 sublimesSublimation of an element or compound is a transition from the solid to gas phase with no intermediate liquid stage. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below the triple point ....
, creating enormous winds that sweep off the poles as fast as 400 km/h. These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like
frostFrost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air. Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. There are many types of...
and large
cirrus cloudCirrus clouds generally refer to atmospheric clouds that are characterized by thin, wisplike strands, often accompanied by tufts, leading to their common name of mare's tail. Sometimes these clouds are so extensive that they are virtually indistinguishable from one another, forming a sheet of...
s. Clouds of water-ice were photographed by the
OpportunityOpportunity, mission designation MER-B , is the second of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully at Meridiani Planum on Mars on January 25, 2004 05:05 Ground UTC , three weeks after its twin Spirit had landed on the other side of the planet...
rover in 2004.
Climate
Of all the planets, Mars's seasons are the most Earth-like, due to the similar tilts of the two planets' rotational axes. However, the lengths of the Martian seasons are about twice those of Earth's, as Mars’ greater distance from the Sun leads to the Martian year being about two Earth years in length. Martian surface temperatures vary from lows of about −140
°CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(−220 °F) during the polar winters to highs of up to 20 °C (68 °F) in summers. The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure, and the low
thermal inertiaVolumetric heat capacity describes the ability of a given volume of a substance to store internal energy while undergoing a given temperature change, but without undergoing a phase change. It is different from specific heat capacity in that the VHC depends on the volume of the material, while the...
of Martian soil.
If Mars had an Earth-like orbit, its seasons would be similar to Earth's because its
axial tiltIn astronomy, axial tilt is the angle between an object's rotational axis and a line perpendicular to its orbital plane. The angle is measured between the line perpendicular to object's orbital plane and object's rotational axis passing through north pole at which the planet appears to rotate...
is similar to Earth's. However, the comparatively large eccentricity of the Martian orbit has a significant effect. Mars is near
perihelionIn celestial mechanics, an apsis, plural apsides is the point of greatest or least distance of the elliptical orbit of an object from its center of attraction, which is generally the center of mass of the system....
when it is summer in the southern hemisphere and winter in the north, and near
aphelionIn celestial mechanics, an apsis, plural apsides is the point of greatest or least distance of the elliptical orbit of an object from its center of attraction, which is generally the center of mass of the system....
when it is winter in the southern hemisphere and summer in the north. As a result, the seasons in the southern hemisphere are more extreme and the seasons in the northern are milder than would otherwise be the case. The summer temperatures in the south can reach up to 30 °C (54 °F)
warmer than the equivalent summer temperatures in the north.
Mars also has the largest
dust stormA dust storm or sandstorm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front blows loose sand and dust from a dry surface. Particles are transported by saltation and suspension, causing soil erosion from one place and deposition in another...
s in our Solar System. These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase the global temperature.
The polar caps at both poles consist primarily of water ice. However, there is dry ice present on their surfaces. Frozen carbon dioxide (dry ice) accumulates as a thin layer about one metre thick on the north cap in the northern winter only, while the south cap has a permanent dry ice cover about eight metres thick.
The northern polar cap has a diameter of about 1,000 kilometres during the northern Mars summer,
and contains about 1.6 million cubic kilometres of ice, which if spread evenly on the cap would be 2 kilometres thick. (This compares to a volume of 2.85 million cubic kilometres for the
Greenland ice sheetThe Greenland ice sheet is a vast body of ice covering 1.71 million km², roughly 80% of the surface of Greenland. It is the second largest ice body in the World, after the Antarctic Ice Sheet. The ice sheet is almost 2,400 kilometers long in a north-south direction, and its greatest width is 1,100...
.) The southern polar cap has a diameter of 350 km and a thickness of 3 km. The total volume of ice in the south polar cap plus the adjacent layered deposits has also been estimated at 1.6 million cubic kilometres. Both polar caps show spiral troughs, which are believed to form as a result of differential solar heating, coupled with the sublimation of ice and condensation of water vapor. Both polar caps shrink and regrow following the temperature fluctuation of the Martian seasons.
Evolution
Recent exploration of Mars has revealed evidence of several defining moments in its history. For example, the remnants of a magnetic field suggest that something more than the mass of Mars once kept its interior molten; the ancient presence of water would have required an atmosphere thicker than that of today; and the Northern Basin records a massive and disruptive impact. Possible explanations include:
- A massive satellite, perhaps a captured asteroid, caused enough tidal heating to melt the interior enough to generate a substantial magnetic field. The field protected the Martian atmosphere from the Solar wind, allowing liquid water to remain on the surface.
- A massive impact removes the crust of one hemisphere and strips Mars of its atmosphere This may have been the satellite, whose orbit could have decayed. from tidal forces. The entire crust shifts to a more stable configuration with the impact basin centered at the north pole and Mars' massive volcanoes near the equator. Without tidal heating from the satellite, the magnetic field fades, and Solar wind striking the surface prevents the atmosphere from reforming.
- The lack of stabilizing satellite allows significant wobble on the order of five million years. This periodically warms the polar regions enough for at least some liquid water to form, and leaves striations in the polar ice cap.
Orbit and rotation
Mars’ average distance from the Sun is roughly 230 million km (1.5 AU) and its orbital period is 687 (Earth) days. The solar day (or
solVarious schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...
) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours.
Mars's axial tilt is 25.19 degrees, which is similar to the axial tilt of the Earth. As a result, Mars has seasons like the Earth, though on Mars they are nearly twice as long given its longer year. Mars passed its perihelion in April 2009 and its aphelion in May 2008. It next reaches perihelion in May 2011 and aphelion in March 2010.
Mars has a relatively pronounced
orbital eccentricityIn astrodynamics, under standard assumptions, any orbit must be of conic section shape. The eccentricity of this conic section, the orbit's eccentricity, is an important parameter of the orbit that defines its absolute shape...
of about 0.09; of the seven other planets in the Solar System, only
MercuryFor the liquid metallic element, see Mercury .Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three...
shows greater eccentricity. However, it is known that in the past Mars has had a much more circular orbit than it does currently. At one point 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. The Mars cycle of eccentricity is 96,000 Earth years compared to the Earth's cycle of 100,000 years. However, Mars also has a much longer cycle of eccentricity with a period of 2.2 million Earth years, and this overshadows the 96,000-year cycle in the eccentricity graphs. For the last 35,000 years Mars' orbit has been getting slightly more eccentric because of the gravitational effects of the other planets. The closest distance between the Earth and Mars will continue to mildly decrease for the next 25,000 years.
The image to the left shows a comparison between Mars and CeresCeres, formal designation 1 Ceres, is the smallest identified dwarf planet in the Solar System and the only one in the asteroid belt. It was discovered on 1 January 1801, by Giuseppe Piazzi, and is named after the Roman goddess Ceres — the goddess of growing plants, the harvest, and motherly...
, a dwarf planetA dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but has not cleared its neighbouring region of planetesimals and is not a satellite. More explicitly, it has to have sufficient mass to...
in the Asteroid BeltThe asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets...
, as seen from the north eclipticThe ecliptic is the apparent path that the Sun traces out in the sky during the year, appearing to move eastwards on an imaginary spherical surface, the celestial sphere, relative to the fixed stars. More accurately, it is the intersection of the celestial sphere with the ecliptic plane, which is...
pole, while the image to the right is as seen from the ascending node. The segments of orbits south of the ecliptic are plotted in darker colors. The perihelia (q) and aphelia (Q) are labelled with the date of the nearest passage. |
Moons
Mars has two tiny natural moons,
PhobosPhobos is the larger and closer of two small moons of Mars, the other being Deimos. It is named after the Greek god Phobos , a son of Ares...
and
DeimosDeimos , is the smaller and outer of Mars’ two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:...
, which orbit very close to the planet. Their known composition suggests the moons are captured asteroids but their origin remains uncertain.
Both satellites were discovered in 1877 by
Asaph HallAsaph Hall III was an American astronomer who is most famous for having discovered the moons of Mars in 1877...
, and are named after the characters
PhobosPhobos is the embodiment of fear and horror in Greek mythology. He is the offspring of Ares and Aphrodite. He was known for accompanying Ares into battle along with his brother, Deimos, the goddess Enyo, and his father’s attendants. Timor is his Roman equivalent.-Genealogy:Phobos is the son of...
(panic/fear) and
DeimosIn Greek mythology, Deimos was the personification of dread.He was the son of Ares and Aphrodite. He, his twin brother Phobos and the goddess Enyo accompanied Ares into battle, as well as his father's attendants, Trembling, Fear, Dread, and Panic...
(terror/dread) who, in
Greek mythologyGreek mythology is the body of myths and legends belonging to the ancient Greeks concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
, accompanied their father
AresIn Greek mythology, Ares is the son of Zeus and Hera. Though often referred to as the Olympian god of warfare, he is more accurately the god of bloodlust, or slaughter personified: "Ares is apparently an ancient abstract noun meaning throng of battle, war."-Etymology:Ares is the god of war...
, god of war, into battle. Ares was known as Mars to the Romans.
From the surface of Mars, the motions of Phobos and Deimos appear very different from that of our own moon. Phobos rises in the west, sets in the east, and rises again in just 11 hours. Deimos, being only just outside
synchronous orbitA synchronous orbit is an orbit in which an orbiting body has a period equal to the average rotational period of the body being orbited , and in the same direction of rotation as that body.-Properties:...
—where the orbital period would match the planet's period of rotation—rises as expected in the east but very slowly. Despite the 30 hour orbit of Deimos, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars, then just as long again to rise.
Because Phobos' orbit is below synchronous altitude, the
tidal forceThe tidal force is a secondary effect of the force of gravity and is responsible for the tides. It arises because the gravitational force exerted on one body by a second body is not constant across its diameter...
s from the planet Mars are gradually lowering its orbit. In about 50 million years it will either crash into Mars’ surface or break up into a ring structure around the planet.
The origin of the two moons is not well understood. Their low albedo and
carbonaceous chondriteCarbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 7 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites...
composition are similar to asteroids and capture remains the favored theory. Phobos' unstable orbit would seem to point towards a relatively recent capture. But both have
circular orbitthumb|200px|Two bodies with a slight difference in mass orbiting around a common [[barycenter]] with circular orbits.In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0...
s, very near the equator, which is very unusual for captured objects and the required capture dynamics are complex. Accretion early in Mars' history is also plausible but does not account for the moons' composition resembling asteroids rather than Mars itself. A third possibility is the involvement of a third body or some kind of impact disruption.
Life
The current understanding of
planetary habitabilityPlanetary habitability is the measure of a planet's or a natural satellite's potential to sustain life. Life may develop directly on a planet or satellite or be transferred to it from another body, a theoretical process known as panspermia...
—the ability of a world to develop and sustain life—favors planets that have liquid water on their surface. This most often requires that the orbit of a planet lie within the habitable zone, which for the Sun currently extends from just beyond Venus to about the
semi-major axisIn geometry, the semi-major axis is used to describe the dimensions of ellipses and hyperbolae.- Ellipse :The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
of Mars. During perihelion Mars dips inside this region, but the planet's thin (low-pressure) atmosphere prevents liquid water from existing over large regions for extended periods. The past flow of liquid water, however, demonstrates the planet's potential for habitability. Recent evidence has suggested that any water on the Martian surface would have been too salty and acidic to support terran life.
The lack of a magnetosphere and extremely thin atmosphere of Mars are a greater challenge: the planet has little
heat transferHeat transfer is the transition of thermal energy from a hotter object to a cooler object...
across its surface, poor insulation against bombardment and the
solar windThe solar wind is a stream of charged particles ejected from the upper atmosphere of the sun. It consists mostly of electrons and protons with energies of about 1 keV. The stream of particles varies in temperature and speed with the passage of time...
, and insufficient atmospheric pressure to retain water in a liquid form (water instead sublimates to a gaseous state). Mars is also nearly, or perhaps totally, geologically dead; the end of volcanic activity has stopped the recycling of chemicals and minerals between the surface and interior of the planet.
Evidence suggests that the planet was once significantly more habitable than it is today, but whether living
organismIn biology, an organism is any living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole...
s ever existed there is still unclear.
The
Viking probesNASA's Viking program consisted of a pair of space probes sent to Mars, Viking 1 and Viking 2. Each vehicle was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites, and had some apparently positive results, including a temporary increase of CO
2 production on exposure to water and nutrients. However this sign of life was later disputed by many scientists, resulting in a continuing debate, with NASA scientist
Gilbert LevinGilbert Levin is an American engineer, the founder of Spherix and famous for experiments on Mars soil by the Viking Program and the development of tagatose.Levin is a member of the "International Committee Against Mars Sample Return" .....
asserting that Viking may have found life. A re-analysis of the now 30-year-old Viking data, in light of modern knowledge of
extremophileAn extremophile is an organism that thrives in and even may require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth...
forms of life, has suggested that the Viking tests were also not sophisticated enough to detect these forms of life. The tests may even have killed a (hypothetical) life form. Tests conducted by the Phoenix Mars Lander have shown that the soil has a very alkaline
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
and it contains magnesium, sodium, potassium and chloride. The soil nutrients may be able to support life, but life would still have to be shielded from the intense ultraviolet light.
At the Johnson space center lab, some curious shapes have been found in the Martian
meteoriteA meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
ALH84001Allan Hills 84001 is a meteorite found in Allan Hills, Antarctica on December 27, 1984 by a team of US meteorite hunters from the ANSMET project. Like other members of the group of SNCs , ALH 84001 is thought to be from Mars. On discovery, its mass was 1.93 kg...
. Some scientists propose that these geometric shapes could be fossilized microbes extant on Mars before the meteorite was blasted into space by a meteor strike and sent on a 15 million-year voyage to Earth. Also, small quantities of
methaneMethane is a chemical compound with the chemical formula . It is the simplest alkane, and the principal component of natural gas. Methane's bond angles are 109.5 degrees. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane and its clean...
and
formaldehydeFormaldehyde is a chemical compound with the formula CH2O. It is the simplest aldehyde. Formaldehyde also exists as the cyclic trimer trioxane and the polymer paraformaldehyde. It exists in water as the hydrate H2C2. Aqueous solutions of formaldehyde are referred...
recently detected by Mars orbiters are both claimed to be hints for life, as these
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s would quickly break down in the Martian atmosphere. It is possible that these compounds may be replenished by volcanic or geological means such as serpentinization.
Exploration
Dozens of
spacecraftA spacecraft is a craft or machine designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as...
, including
orbiterAn orbiter is a space probe that orbits a planet or natural satellite without landing on it in order to study its surface from a distance.-Asteroids:*NEAR Shoemaker...
s,
landersA lander is a spacecraft which descends toward and comes to rest on the surface of an astronomical body. For bodies with atmospheres, the landing is called atmospheric reentry and the lander descends as a re-entry vehicle...
, and
roversThere are two main types of rovers.A rover is a space exploration vehicle designed to move across the surface of a planet or other astronomical body. Some rovers have been designed to transport members of a human spaceflight crew; others have been partially or fully autonomous robots...
, have been sent to Mars by the
Soviet UnionThe Soviet space program refers to the rocketry and space exploration programs conducted by the Soviet Union from the 1930s until its dissolution in 1991...
, the
United StatesThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
, Europe, and Japan to study the planet's surface, climate, and geology. The current price of transporting material from the surface of
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
to the surface of Mars is approximately 309000
USDThe United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
/
kgThe kilogram is the base unit of mass in the International System of Units .[The spelling kilogram is the modern spelling used by the International Bureau of Weights and Measures , the U.S...]
.
Roughly two-thirds of all spacecraft destined for Mars have failed in one manner or another before completing or even beginning their missions. While this high failure rate can be ascribed to technical problems, enough have either failed or lost communications for causes unknown for some to search for other explanations. Examples include an Earth-Mars "
Bermuda TriangleThe Bermuda Triangle, also known as the Devil's Triangle, is a region in the western part of the North Atlantic Ocean in which a number of aircraft and surface vessels are alleged to have mysteriously disappeared and cannot be explained as human error, piracy, equipment failure, or natural disasters...
", a Mars Curse, or even the long-standing NASA in-joke, the "Great Galactic Ghoul" that feeds on Martian spacecraft.
Past missions
The first successful fly-by mission to Mars was NASA's
Mariner 4Mariner 4 was the fourth in a series of spacecraft, launched on November 28, 1964, intended for planetary exploration in a flyby mode and performed the first successful flyby of the planet Mars, returning the first pictures of the Martian surface...
, launched in 1964. On November 14, 1971
Mariner 9Mariner 9 was a NASA space probe orbiter that helped in the exploration of Mars and was part of the Mariner program...
became the first space probe to orbit another planet when it entered into orbit around Mars. The first successful objects to land on the surface were two
SovietThe Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the , tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated СССР, SSSR. The common short name is Soviet Union, from , Sovetskiy Soyuz...
probes,
Mars 2The Mars program was a series of Mars unmanned landers and orbiters launched by the Soviet Union in the early 1970s.The Mars 2 and Mars 3 missions consisted of identical spacecraft, each with an orbiter and an attached lander; they were the first human artifacts to impact the surface of Mars...
and
Mars 3The Mars program was a series of Mars unmanned landers and orbiters launched by the Soviet Union in the early 1970s.The Mars 2 and Mars 3 missions consisted of identical spacecraft, each with an orbiter and an attached lander; they were the first human artifacts to touch down on Mars...
from the
Mars probe programThe Mars program was a series of Mars unmanned landers and orbiters launched or attempted to launch by the Soviet Union in the 1960s-1970s.- First generation - Marsnik design :...
, launched in 1971, but both lost contact within seconds of landing. Then came the 1975 NASA launches of the
Viking programNASA's Viking program consisted of a pair of space probes sent to Mars, Viking 1 and Viking 2. Each vehicle was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
, which consisted of two orbiters, each having a lander; both landers successfully touched down in 1976.
Viking 1Viking 1 was the first of two spacecraft sent to Mars as part of NASA's Viking program. It was the first spacecraft to successfully land on Mars and perform its mission, and holds the record for the longest Mars surface mission of 6 years and 116 days .- Mission :Following launch using a...
remained operational for six years,
Viking 2The Viking 2 mission was part of the Viking program to Mars, and consisted of an orbiter and a lander essentially identical to that of the Viking 1 mission. The Viking 2 lander operated on the surface for 1,281 Mars days and was turned off on 11 April 1980 when its batteries failed...
for three. The Viking landers relayed color panoramas of Mars and the orbiters mapped the surface so well that the images remain in use.
The Soviet probes
Phobos 1 and 2The Phobos program was an unmanned space mission consisting of two probes launched by the Soviet Union to study Mars and its moons Phobos and Deimos. Phobos 2 became a Mars orbiter and returned 38 images with a resolution of up to 40 meters...
were sent to Mars in 1988 to study Mars and its two moons. Phobos 1 lost contact on the way to Mars. Phobos 2, while successfully photographing Mars and Phobos, failed just before it was set to release two landers on Phobos's surface.
Following the 1992 failure of the
Mars ObserverMars Observer was an unmanned spacecraft designed to study the geoscience and climate of Mars. The first of the proposed Observer series of planetary missions, it was launched by NASA on September 25, 1992. Three days before Mars Observer was scheduled to enter the orbit of Mars, contact with the...
orbiter, NASA launched the
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
in 1996. This mission was a complete success, having finished its primary mapping mission in early 2001. Contact was lost with the probe in November 2006 during its third extended program, spending exactly 10 operational years in space. Only a month after the launch of the Surveyor, NASA launched the
Mars PathfinderThe Mars Pathfinder later called The Carl Sagan Memorial Station was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor was launched. After a 7-month voyage it landed on Ares Vallis, in a region called Chryse Planitia on Mars, in the Oxia Palus...
, carrying a robotic exploration vehicle Sojourner, which landed in the
Ares VallisAres Vallis is a valley on Mars which appears to have been carved by fluids, perhaps water. The valley 'flows' northwest out of the hilly Margaritifer Terra, where the Iani Chaos depression is connected to the beginning of Ares Vallis by a 100 km wide transition zone centred around 342.5°...
on Mars in the summer of 1997. This mission was also successful, and received much publicity, partially due to the many images that were sent back to Earth.
The most recent mission to Mars was the NASA
PhoenixPhoenix was a robotic spacecraft on a space exploration mission on Mars under the Mars Scout Program. The Phoenix lander descended on Mars on May 25, 2008...
Mars lander, which launched August 4, 2007 and arrived on the north polar region of Mars on May 25, 2008. The lander has a robotic arm with a 2.5 m reach and capable of digging a metre into the Martian soil. The lander has a microscopic camera capable of resolving to one-thousandth the width of a human hair, and discovered a substance at its landing site on June 15, 2008, which was confirmed to be water ice on June 20. The mission was declared concluded on November 10, 2008, after engineers were unable to contact the craft.
Current missions
In 2001 NASA launched the successful Mars Odyssey orbiter, which is still in orbit as of March 2009, and the ending date has been extended to September 2010. Odyssey's
Gamma Ray SpectrometerA Gamma-Ray Spectrometer, or , is an instrument for measuring the distribution of the intensity of gamma radiation versus the energy of each photon....
detected significant amounts of hydrogen in the upper metre or so of Mars's
regolithRegolith is a layer of loose, heterogeneous material covering solid rock. The term is a combination of two Greek words: Rhegos , which means blanket, and Lithos , which means rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, some asteroids,...
. This hydrogen is thought to be contained in large deposits of water ice.
In 2003, the
European Space Agency|owner = |headquarters = Paris|spaceport = Guiana Space Centre|image = ESA LOGO.svg|size = 240px|acronym = ESA|established = 1975|administrator = Jean-Jacques Dordain...
(ESA) launched the Mars Express craft, consisting of the Mars Express Orbiter and the lander
Beagle 2Beagle 2 was an unsuccessful British landing spacecraft that formed part of the European Space Agency's 2003 Mars Express mission. It is not known for certain whether the lander reached the Martian surface; all contact with it was lost upon its separation from the Mars Express six days before its...
. Beagle 2 failed during descent and was declared lost in early February 2004. In early 2004 the
Planetary Fourier SpectrometerThe Planetary Fourier Spectrometer is an infrared spectrometer built by the Istituto Nazionale di Astrofisica along with the Istituto di Fisica dello spazio Interplanetario and the Consiglio Nazionale delle Ricerche...
team announced it had detected methane in the Martian atmosphere. ESA announced in June 2006 the discovery of
auroraeAuroras, sometimes called the northern and southern lights or aurorae , are natural light displays in the sky, usually observed at night, particularly in the polar regions. They typically occur in the ionosphere. They are also referred to as polar auroras...
on Mars.
Also in 2003, NASA launched the twin Mars Exploration Rovers named
SpiritSpirit, mission designation MER-A , is the first of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully on Mars on 04:35 Ground UTC on January 4, 2004, three weeks before its twin Opportunity landed on the other side of the planet...
(MER-A) and
OpportunityOpportunity, mission designation MER-B , is the second of the two rovers of NASA's Mars Exploration Rover Mission. It landed successfully at Meridiani Planum on Mars on January 25, 2004 05:05 Ground UTC , three weeks after its twin Spirit had landed on the other side of the planet...
(MER-B). Both missions landed successfully in January 2004 and have met or exceeded all their targets. Among the most significant scientific returns has been conclusive evidence that liquid water existed at some time in the past at both landing sites. Martian dust devils and windstorms have occasionally cleaned both rovers' solar panels, and thus increased their lifespan.
On August 12, 2005 the NASA
Mars Reconnaissance OrbiterNASA's Mars Reconnaissance Orbiter is a multipurpose spacecraft designed to conduct reconnaissance and exploration of Mars from orbit....
probe was launched toward the planet, arriving in orbit on March 10, 2006 to conduct a two-year science survey. The orbiter will map the Martian terrain and weather to find suitable landing sites for upcoming lander missions. It also contains an improved telecommunications link to Earth, with more bandwidth than all previous missions combined. The Mars Reconnaissance Orbiter snapped the first image of a series of active
avalancheAn avalanche is a rapid flow of snow down a slope, from either natural triggers or human activity. Typically occurring in mountainous terrain, an avalanche can mix air and water with the descending snow...
s near the planet's
north poleThe North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets the Earth's surface...
, scientists said March 3, 2008.
The
DawnDawn is a robotic spacecraft sent by NASA on a space exploration mission to the two most massive members of the asteroid belt: the asteroid Vesta and the dwarf planet Ceres. Launched September 27, 2007, Dawn is scheduled to explore Vesta between 2011 and 2012, and Ceres in 2015...
spacecraft flew by Mars in February 2009 for a gravity assist on its way to investigate
Vesta4 Vesta is the second most massive object in the asteroid belt, with a mean diameter of about 530 km and an estimated mass of 9% of the mass of the entire asteroid belt...
and then Ceres.
Future missions
Phoenix will be followed by the
Mars Science LaboratoryThe Mars Science Laboratory , known as Curiosity, is a NASA rover scheduled to be launched between October and December 2011 and perform the first-ever precision landing on Mars. The MSL rover will be over five times as heavy and carry over ten times the weight in scientific instruments as one of...
in 2011, a bigger, faster (90
m/hMetre per hour is a metric unit of both speed and velocity . Its symbol is m/h or m·h−1 Metre per hour (American spelling: meter per hour) is a metric unit of both speed (scalar) and velocity (Vector (geometry)). Its symbol is m/h or m·h−1 Metre per hour...
), and smarter version of the Mars Exploration Rovers. Experiments include a laser chemical sampler that can deduce the make-up of rocks at a distance of 13 m.
The joint Russian and Chinese
Phobos-GruntPhobos-Grunt is a planned Russian sample return mission to Phobos, one of the moons of Mars. The Chinese Mars orbiter Yinghuo-1 will be sent together with the mission. Scheduled for launch in 2011, Phobos-Grunt will be the first Russian interplanetary mission since the failed Mars 96 mission...
mission to return samples of Mars's moon Phobos (
grunt is the Russian word for soil) was originally scheduled for October 2009, but the mission was postponed till the next launch window in 2011. On September 15, 2008, NASA announced MAVEN, a robotic mission in 2013 to provide information about Mars' atmosphere. In 2018 the ESA plans to launch its first Rover to Mars; the
ExoMarsExoMars is a European-led mission currently under development by the European Space Agency that would send a robotic rover to the surface of Mars...
rover will be capable of drilling 2 m into the soil in search of organic molecules.
The Finnish-Russian
MetNetMetNet is an atmospheric science mission to Mars, initiated and defined by the Finnish Meteorological Institute. The mission includes sending several tens of MetNet Landers on the Martian surface...
mission will land tens of small vehicles on the Martian surface to establish a widespread surface observation network to investigate the planet's atmospheric structure, physics and meteorology. A precursor mission using one or a few landers is scheduled for launch in 2009 or 2011. One possibility is a piggyback launch on the Russian Phobos-Grunt mission. Other launches will take place in the launch windows extending to 2019.
Manned Mars explorationA manned mission to Mars has not taken place but is the subject of science fiction, engineering, and scientific proposals and plans throughout the 20th Century and into the 21st Century...
by the United States has been explicitly identified as a long-term goal in the
Vision for Space ExplorationThe Vision for Space Exploration is the United States space policy announced on January 14, 2004 by then-U.S. President George W. Bush. It is seen as a response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a way to regain public enthusiasm for space...
announced in 2004 by the then US President
George W. BushGeorge Walker Bush was the 43rd President of the United States from 2001 to 2009 and the 46th Governor of Texas from 1995 to 2000....
. NASA and
Lockheed MartinLockheed Martin is a multinational aerospace manufacturer, global security and advanced technology company formed in 1995 by the merger of Lockheed with Martin Marietta. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area. Lockheed Martin employs 146,000 people...
have begun work on the
OrionOrion is a spacecraft design currently under development by the United States space agency NASA. Each Orion spacecraft will carry a crew of four to six astronauts. The spacecraft is designed to be launched by the Ares I, a launch vehicle, also currently under development...
spacecraft, formerly the Crew Exploration Vehicle, which is currently scheduled to send a human expedition to Earth's moon by 2020 as a stepping stone to an expedition to Mars thereafter. On September 28, 2007, NASA administrator
Michael D. GriffinMichael Douglas Griffin is an American physicist, aerospace engineer and the former Administrator of NASA, from April 13, 2005 to January 20, 2009. As the chief of America's space agency, Dr. Griffin oversaw such areas as the future of human spaceflight, the fate of the Hubble telescope and NASA's...
stated that NASA aims to put a man on Mars by 2037.
ESA hopes to land humans on Mars between 2030 and 2035. This will be preceded by successively larger probes, starting with the launch of the ExoMars probe and a Mars Sample Return Mission.
Mars DirectMars Direct is a proposal for a relatively low-cost manned mission to Mars with current rocket technology. The plan was originally detailed in a research paper by Robert Zubrin and David Baker in 1990. The mission was expanded upon in Zubrin's 1996 book The Case for Mars...
, an extremely low-cost human mission proposed by Bob Zubrin, a founder of the
Mars SocietyThe Mars Society is an international space advocacy non-profit organization dedicated to encouraging the exploration and settlement of Mars. Founded by Robert Zubrin and others in mid-1998 and attracting the support of notable science fiction writers and filmmakers , the organization is dedicated...
, uses heavy-lift
Saturn VThe Saturn V was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs from 1967 until 1973. In total NASA launched thirteen Saturn V rockets with no loss of payload. It remains the largest and most powerful launch vehicle ever brought to operational status from a...
class rockets, such as the Space X Falcon 9, or, the
Ares VThe Ares V is the cargo launch component of the upcoming Constellation program, which will replace the Space Shuttle after its retirement in 2010...
, to skip orbital construction, LEO rendezvous, and lunar fuel depots. A modified proposal, called "Mars to Stay", involves not returning the first immigrant/explorers immediately, if ever. Dean Unick has suggested the cost of sending a four to six person team is one fifth to one tenth the cost of returning that same four to six person team; twenty settlers could be sent for the cost of returning four.
Astronomy on Mars
With the existence of various orbiters, landers, and rovers, it is now possible to study
astronomyAstronomy is the scientific study of celestial objects and phenomena that originate outside the Earth's atmosphere...
from the Martian skies. While Mars’ moon Phobos appears about one third the
angular diameterThe angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...
of the full Moon as it appears from Earth, Deimos appears more or less star-like, and appears only slightly brighter than Venus does from Earth.
There are also various phenomena well-known on Earth that have now been observed on Mars, such as
meteorMETEOR is a metric for the evaluation of machine translation output. The metric is based on the harmonic mean of unigram precision and recall, with recall weighted higher than precision...
s and auroras. A
transit of the Earth as seen from MarsA transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars. During a transit, Earth could be seen from Mars as a small black disc moving across the face of the Sun...
will occur on November 10, 2084. There are also
transits of MercuryA transit of Mercury across the Sun as seen from Mars takes place when the planet Mercury passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars...
and
transits of VenusA transit of Venus across the Sun as seen from Mars takes place when the planet Venus passes directly between the Sun and Mars, obscuring a small part of the Sun's disc for an observer on Mars...
, and the moon Deimos is of sufficiently small angular diameter that its partial "eclipses" of the Sun are best considered transits (see
Transit of Deimos from MarsA transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Sun's disc for an observer on Mars...
).
Viewing
To the naked eye, Mars usually appears a distinct yellow, orange, or reddish color, and varies in brightness more than any other planet as seen from Earth over the course of its orbit. However the actual color of Mars is closer to
butterscotchButterscotch is a type of confectionery whose primary ingredients are brown sugar and butter. Other ingredients such as corn syrup, cream, vanilla, and salt are typically part of the recipe also. The ingredients for butterscotch are similar to toffee; the major difference is that the sugar is...
, and the redness seen is actually just dust in the planets atmosphere; considering this
NASAThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
's Spirit rover has taken pictures of a greenish-brown, mud-colored landscape with blue-grey rocks and patches of light red colored sand. The
apparent magnitudeThe apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, normalized to the value it would have in the absence of the atmosphere...
of Mars varies from +1.8 at conjunction to as high as −2.9 at
perihelicIn celestial mechanics, an apsis, plural apsides is the point of greatest or least distance of the elliptical orbit of an object from its center of attraction, which is generally the center of mass of the system....
oppositionOpposition is a term used in positional astronomy to indicate when one celestial body is on the opposite side of the sky when viewed from a particular place . In particular, two planets are in opposition to each other when their ecliptic longitudes differ by 180°.The symbol of opposition is...
. When farthest away from the Earth, it is more than seven times as far from the latter as when it is closest. When least favorably positioned, it can be lost in the Sun's glare for months at a time. At its most favorable times—at 15- or 17-year intervals, and always between late July and late September—Mars shows a wealth of surface detail to a
telescopeA telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century...
. Especially noticeable, even at low magnification, are the
polar ice capA polar ice cap is a high latitude region of a planet or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor any geological requirement for it to be over land; only that it must be a body of...
s.
The point of Mars’ closest approach to the Earth is known as opposition. The length of time between successive oppositions, or the synodic period, is 780 days. Because of the eccentricities of the orbits, the times of opposition and minimum distance can differ by up to 8.5 days. The minimum distance varies between about 55 and 100 million km due to the planets'
ellipticalIn mathematics, an ellipse is the bounded case of a conic section, the geometric shape that results from cutting a circular conical or cylindrical surface with an oblique plane...
orbits. The next Mars opposition will occur on January 29, 2010.
As Mars approaches opposition it begins a period of retrograde motion, which means it will appear to move backwards in a looping motion with respect to the background stars.
2003 closest approach
On August 27, 2003, at 9:51:13 UT, Mars made its closest approach to Earth in nearly 60,000 years: 55,758,006 km . This occurred when Mars was one day from opposition and about three days from its perihelion, making Mars particularly easy to see from Earth. The last time it came so close is estimated to have been on September 12,
57 617 BCThe Middle Paleolithic is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle Paleolithic in African archeology. The Middle Paleolithic and the Middle Stone Age...
, the next time being in 2287.
However, this record approach was only very slightly closer than other recent close approaches. For instance, the minimum distance on August 22, 1924 was , and the minimum distance on August 24, 2208 will be .
Historical observations
The history of observations of Mars is marked by the oppositions of Mars, when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the perihelic oppositions of Mars which occur every 15 or 17 years, and are distinguished because Mars is close to perihelion, making it even closer to Earth.
AristotleAristotle was a Greek philosopher, a student of Plato and teacher of Alexander the Great. He wrote on many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, politics, government, ethics, biology, and zoology.Together with Plato and Socrates , Aristotle is one of...
was among the first known writers to describe observations of Mars, noting that, as it passed behind the Moon, it was farther away than was originally believed.
The only
occultationAn occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy and can also be used in a general sense to describe when an object in the foreground occults objects in the background...
of Mars by Venus observed was that of October 13, 1590, seen by
Michael MaestlinMichael Maestlin was a German astronomer and mathematician, known for being the mentor of Johannes Kepler.-Career:...
at
HeidelbergHeidelberg is a city in Baden-Württemberg, Germany. As of 2008, over 145,000 people live within the city's area. Heidelberg is a unitary authority...
. In 1609, Mars was viewed by Galileo, who was first to see it via telescope.
Martian 'canals'
By the 19th century, the resolution of telescopes reached a level sufficient for surface features to be identified. In September 1877, a perihelic opposition of Mars occurred on September 5. In that year, Italian astronomer
Giovanni SchiaparelliGiovanni Virginio Schiaparelli was an Italian astronomer and science historian. He studied at the University of Turin and Berlin Observatory. In 1859-1860 he worked in Pulkovo Observatory and then worked for over forty years at Brera Observatory...
, then in
MilanMilan in Italy, is the capital of the region of Lombardia and of the province of Milan. The city proper has a population of about 1.3 million, while the urban area is the fifth largest in the E.U. with an estimated population of 4.3 million...
, used a 22 cm telescope to help produce the first detailed map of Mars. These maps notably contained features he called
canali, which were later shown to be an
optical illusionAn optical illusion is characterized by visually perceived images that differ from objective reality. The information gathered by the eye is processed in the brain to give a percept that does not tally with a physical measurement of the stimulus source...
. These
canali were supposedly long straight lines on the surface of Mars to which he gave names of famous rivers on Earth. His term, which means 'channels' or 'grooves', was popularly mistranslated in English as
canals.
Influenced by the observations, the orientalist
Percival LowellPercival Lawrence Lowell was a businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death...
founded an
observatoryLowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory is among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
which had a 300 and 450 mm telescope. The observatory was used for the exploration of Mars during the last good opportunity in 1894 and the following less favorable oppositions. He published several books on Mars and life on the planet, which had a great influence on the public. The
canali were also found by other astronomers, like Henri Joseph Perrotin and Louis Thollon in
NiceNice is a city in southern France located on the Mediterranean coast, between Marseille, France, and Genoa, Italy, with 347 060 inhabitants in the 2006 estimate...
, using one of the largest telescopes of that time.
The seasonal changes (consisting of the diminishing of the polar caps and the dark areas formed during Martian summer) in combination with the canals lead to speculation about life on Mars, and it was a long held belief that Mars contained vast seas and vegetation. The telescope never reached the resolution required to give proof to any speculations. However, as bigger telescopes were used, fewer long, straight
canali were observed. During an observation in 1909 by
FlammarionNicolas Camille Flammarion was a French astronomer and author. He is commonly referred to as Camille Flammarion.-Life:Camille Flammarion was born in Montigny-le-Roi, Haute-Marne, France...
with a 840 mm telescope, irregular patterns were observed, but no
canali were seen.
Even in the 1960s articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars. Detailed scenarios for the metabolism and chemical cycles for a functional ecosystem have been published.
It was not until
spacecraftA spacecraft is a craft or machine designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters space then returns to the Earth. For an orbital spaceflight, a spacecraft enters a closed orbit around the planetary body. Spacecraft used for human spaceflight carry people on board as...
visited the planet during NASA's
Mariner missionsThe Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury...
in the 1960s that these myths were dispelled. The results of the Viking life-detection experiments started an intermission in which the hypothesis of a hostile, dead planet was generally accepted.
Some maps of Mars were made using the data from these missions, but it was not until the
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
mission, launched in 1996 and operated until late 2006, that complete, extremely detailed maps were obtained. These maps are now available online, for example, at
Google MarsGoogle Mars was at first an in-browser version of Google Maps which provides a visible imagery view, like Google Moon, as well as infrared imagery and shaded relief of the planet Mars. Users can toggle between the elevation, visible, and infrared data, in the same manner as switching between map,...
.
Historical connections
Mars is named after the
RomanAncient Rome was a civilization that grew out of a small agricultural community founded on the Italian Peninsula as early as the 10th century BC. Located along the Mediterranean Sea, it became one of the largest empires in the ancient world....
god of warMars was the Roman god of war, the son of Juno and Jupiter, husband of Bellona, and the lover of Venus. He was the most prominent of the military gods that were worshipped by the Roman legions. The martial Romans considered him second in importance only to Jupiter...
. In
BabyloniaBabylonia was a civilization in Lower Mesopotamia , with Babylon as its capital. Babylonia emerged when Hammurabi created an empire out of the territories of the former kingdoms of Sumer and Akkad...
n astronomy, the planet was named after
NergalThe name Nergal refers to a deity in Babylonia with the main seat of his cult at Cuthah represented by the mound of Tell-Ibrahim. Nergal is mentioned in the Hebrew bible as the deity of the city of Cuth : "And the men of Babylon made Succoth-benoth, and the men of Cuth made Nergal"...
, their
deityA deity is a postulated preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....
of fire, war, and destruction, most likely due to the planet's reddish appearance. When the
GreeksAncient Greece is the civilisation belonging to the period of Greek history lasting from the Greek Dark Ages ca. 1100 BC and the Dorian invasion, to 146 BC and the Roman conquest of Greece after the Battle of Corinth. It is generally considered to be the seminal culture which provided the...
equated Nergal with their god of war, Ares, they named the planet Ἄρεως ἀστἡρ (
Areos aster), or "star of Ares". Then, following the
identificationInterpretatio graeca is a Latin term for the common tendency of ancient Greek writers to equate foreign divinities to members of their own pantheon...
of Ares and Mars, it was translated into Latin as
stella Martis, or "star of Mars", or simply
Mars. The Greeks also called the planet Πυρόεις
Pyroeis meaning "fiery". In
Hindu mythologyHindu mythology is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Indian mythology...
, Mars is known as
MangalaIn Jyotish astrology, Mangala is the name for Mars, the red planet. Mars is also called Angaraka or Bhauma in Sanskrit. He is the god of war and is celibate. He is considered the son of Prithvi or Bhumi, the Earth Goddess...
(मंगल). The planet is also called
Angaraka in
SanskritSanskrit is a historical Indo-Aryan language, one of the liturgical languages of Hinduism and Buddhism, and one of the 22 official languages of India. It is also declared as a classical language by the government of India....
, after the celibate god of war, who possesses the signs of
AriesAries is the first astrological sign in the Zodiac, named for the constellation of Aries, called "The Ram" in the Greek tradition, after the golden ram that rescued Phrixos, taking him to the land of Colchis....
and
ScorpioScorpio is the eighth astrological sign in the Zodiac, originating from the constellation of Scorpius. Scorpio is considered a "feminine", negative sign by most modern astrologers. It is also considered a water sign and one of the four fixed signs. Traditionally, the planet Mars has been...
, and teaches the occult sciences. The planet was known by the
EgyptiansAncient Egypt was an ancient civilization of eastern North Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. The civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh, and...
as "
Ḥr Dšr";;;; or "
HorusHorus is one of the oldest and most significant of the deities in the Ancient Egyptian religion who was worshipped from at least the late Predynastic period through to Greco-Roman times. Different forms of Horuses are recorded in history and these are treated as distinct gods by Egyptologists...
the Red". The
HebrewsHebrews are an ancient people defined as descendants of the prophet Eber, son of Shelah.In the Bible, the patriarch Abraham is referred to a single time as the ivri, which is the singular form of the...
named it
Ma'adim (מאדים) — "the one who blushes"; this is where one of the largest canyons on Mars, the
Ma'adim VallisMa'adim Vallis is one of the largest canyons on Mars, about 700 km long and significantly larger than Earth's Grand Canyon. It is over 20 km wide and 2 km deep in some places. It runs from a region of southern lowlands thought to have once contained a large group of lakes north to...
, gets its name. It is known as
al-Mirrikh in Arabic, and
Merih in Turkish. In
UrduUrdu is a Central Indo-Aryan language of the Indo-Iranian branch, belonging to the Indo-European family of languages. It is one of the two official languages of Pakistan. It is also one of the 22 scheduled languages of India and is an official language of five Indian states...
and Persian it is written as
مریخ and known as "Merikh". The etymology of
al-Mirrikh is unknown. Ancient Persians named it
Bahram, the Zoroastrian god of faith and it is written as
بهرام. Ancient Turks called it
Sakit. The Chinese, Japanese,
KoreaKorea is a civilization and formerly unified nation currently divided into two states. Located on the Korean Peninsula, it borders China to the northwest, Russia to the northeast, and is separated from Japan to the east by the Korea Strait....
n and
VietnamVietnam , officially the Socialist Republic of Vietnam , is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea to the east...
ese cultures refer to the planet as 火星, or the
fire star, a name based on the ancient Chinese mythological cycle of
Five elementsThe Wu Xing , or the Five Movements, Five Phases or Five Steps/Stages, are chiefly an ancient mnemonic device, in many traditional Chinese fields....
.
Its symbol, derived from the astrological symbol of Mars, is a circle with a small arrow pointing out from behind. It is a stylized representation of a shield and spear used by the Roman God Mars. Mars in Roman mythology was the God of War and patron of warriors. This symbol is also used in biology to describe the
maleMale refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
sex, and in
alchemyAlchemy is both a philosophy and a practice with an aim of achieving ultimate wisdom as well as immortality, involving the improvement of the alchemist as well as the making of several substances described as possessing unusual properties...
to
symboliseAlchemic symbols, originally devised as part of the protoscience of alchemy, were used to denote some elements and some compounds until the 18th century...
the element iron which was considered to be dominated by Mars whose characteristic red colour is coincidentally due to iron oxide. ♂ occupies
UnicodeUnicode is a computing industry standard allowing computers to consistently represent and manipulate text expressed in most of the world's writing systems...
position U+2642.
Intelligent "Martians"
The popular idea that Mars was populated by intelligent
MartianAs an adjective, the term "martian" is used to describe anything pertaining to the planet Mars.However, a Martian is more usually a hypothetical or fictional native inhabitant of the planet Mars. Historically, life on Mars has often been hypothesized, although there is currently no solid evidence...
s exploded in the late 19th century.
Schiaparelli'sGiovanni Virginio Schiaparelli was an Italian astronomer and science historian. He studied at the University of Turin and Berlin Observatory. In 1859-1860 he worked in Pulkovo Observatory and then worked for over forty years at Brera Observatory...
"canali" observations combined with
Percival Lowell'sPercival Lawrence Lowell was a businessman, author, mathematician, and astronomer who fueled speculation that there were canals on Mars, founded the Lowell Observatory in Flagstaff, Arizona, and formed the beginning of the effort that led to the discovery of Pluto 14 years after his death...
books on the subject put forward the standard notion of a planet that was a drying, cooling, dying world with ancient civilizations constructing irrigation works.
Many other observations and proclamations by notable personalities added to what has been termed "Mars Fever". In 1899 while investigating atmospheric radio noise using his receivers in his Colorado Springs lab, inventor
Nikola TeslaNikola Tesla was an inventor and a mechanical and electrical engineer. He is frequently cited as one of the most important contributors to the birth of commercial electricity and is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th...
observed repetitive signals that he later surmised might have been radio communications coming from another planet, possibly Mars. In a 1901 interview Tesla said:
It was some time afterward when the thought flashed upon my mind that the disturbances I had observed might be due to an intelligent control. Although I could not decipher their meaning, it was impossible for me to think of them as having been entirely accidental. The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another.
Tesla's theories gained support from
Lord KelvinWilliam Thomson, 1st Baron Kelvin , OM, GCVO, PC, PRS, FRSE, was a British mathematical physicist and engineer...
who, while visiting the United States in 1902, was reported to have said that he thought Tesla had picked up Martian signals being sent to the United States. However, Kelvin "emphatically" denied this report shortly before departing America: "What I really said was that the inhabitants of Mars, if there are any, were doubtless able to see New York, particularly the glare of the electricity."
In a
New York Times article in 1901,
Edward Charles PickeringEdward Charles Pickering was an American astronomer and physicist, brother of William Henry Pickering.Along with Carl Vogel, Pickering discovered the first spectroscopic binary stars. He wrote Elements of Physical Manipulations .Pickering attended Boston Latin School, and received his B.S. from...
, director of the
Harvard College ObservatoryThe Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, USA, and was founded in 1839...
, said that they had received a telegram from
Lowell ObservatoryLowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory is among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
in
ArizonaThe State of Arizona is a state located in the southwestern region of the United States. The capital and largest city is Phoenix. The second largest city is Tucson, followed in size by the four Phoenix metropolitan area cities of Mesa, Glendale, Chandler, and Scottsdale.Arizona was the 48th and...
that seemed to confirm that Mars was trying to communicate with the Earth.
Early in December 1900, we received from Lowell Observatory in Arizona a telegram that a shaft of light had been seen to project from Mars (the Lowell observatory makes a specialty of Mars) lasting seventy minutes. I wired these facts to Europe and sent out neostyle copies through this country. The observer there is a careful, reliable man and there is no reason to doubt that the light existed. It was given as from a well-known geographical point on Mars. That was all. Now the story has gone the world over. In Europe it is stated that I have been in communication with Mars, and all sorts of exaggerations have spring up. Whatever the light was, we have no means of knowing. Whether it had intelligence or not, no one can say. It is absolutely inexplicable.
Pickering later proposed creating a set of mirrors in
TexasTexas is the second-largest U.S. state in both area and population, and the largest state in the contiguous United States.The name had wide usage among native Americans, meaning "friends" or "allies"...
with the intention of signaling Martians.
In recent decades, the high resolution mapping of the surface of Mars, culminating in
Mars Global SurveyorThe Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on , the...
, revealed no artifacts of habitation by 'intelligent' life, but pseudoscientific speculation about intelligent life on Mars continues from commentators such as
Richard C. HoaglandRichard C. Hoagland is an American author and a proponent of various conspiracy theories about NASA, lost alien civilizations on the moon and on Mars and other related topics...
. Reminiscent of the
canali controversy, some speculations are based on small scale features perceived in the spacecraft images, such as 'pyramids' and the 'Face on Mars'. Planetary astronomer
Carl SaganCarl Edward Sagan was an American astronomer, astrochemist, author, and highly successful popularizer of astronomy, astrophysics and other natural sciences...
wrote:
Mars has become a kind of mythic arena onto which we have projected our Earthly hopes and fears.
In fiction
The depiction of Mars in fiction has been stimulated by its dramatic red color and by early scientific speculations that its surface conditions not only might support life, but intelligent life.
Thus originated a large number of
science fictionScience fiction is a genre of fiction. It differs from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically-established or scientifically-postulated laws of nature...
scenarios, the best known of which is
H. G. WellsHerbert George Wells was an English author, best known for his work in the science fiction genre. He was also a prolific writer in many genres, including contemporary novels, history, and social commentary....
'
The War of the Worlds, published in 1898, in which Martians seek to escape their dying planet by invading Earth. A subsequent radio version of
The War of the WorldsThe War of the Worlds was an episode of the American radio drama anthology series Mercury Theatre on the Air. It was performed as a Halloween episode of the series on October 30, 1938 and aired over the Columbia Broadcasting System radio network. Directed and narrated by Orson Welles, the episode...
on October 30, 1938 was presented as a live news broadcast, and many listeners mistook it for the truth.
Also influential were Ray Bradbury's
The Martian ChroniclesThe Martian Chronicles is a 1950 science fiction short story collection by Ray Bradbury that chronicles the colonization of Mars by humans fleeing from a troubled and eventually atomically devastated Earth, and the conflict between aboriginal Martians and the new colonists...
, in which human explorers accidentally destroy a Martian civilization,
Edgar Rice BurroughsEdgar Rice Burroughs was an American author, best known for his creation of the jungle hero Tarzan and the heroic Mars adventurer John Carter, although he produced works in many genres.-Biography:...
'
Barsoom seriesBarsoom is a fictional representation of the planet Mars created by American pulp fiction author Edgar Rice Burroughs, who wrote close to 100 swashbuckling action adventure stories in various genres in the first half of the 20th century, and is now best known as the creator of the character Tarzan...
and a number of
Robert A. HeinleinRobert Anson Heinlein was an American science fiction writer. Often called "the dean of science fiction writers", he was one of the most popular, influential, and controversial authors of the genre. He set a high standard for science and engineering plausibility and helped to raise the genre's...
stories before the mid-sixties.
Author
Jonathan SwiftJonathan Swift was an Anglo-Irish satirist, essayist, political pamphleteer , poet and cleric who became Dean of St...
made reference to the moons of Mars, about 150 years before their actual discovery by
Asaph HallAsaph Hall III was an American astronomer who is most famous for having discovered the moons of Mars in 1877...
, detailing reasonably accurate descriptions of their orbits, in the 19th chapter of his novel
Gulliver's TravelsGulliver's Travels , officially Travels into Several Remote Nations of the World, in Four Parts. By Lemuel Gulliver, First a Surgeon, and then a Captain of several Ships, is a novel by Irish writer and clergyman Jonathan Swift that is both a satire on human nature and a parody of the "travellers'...
.
Another reference is found in
C. S. LewisClive Staples Lewis , commonly referred to as C. S. Lewis and known to his friends and family as Jack, was an Irish-born British novelist, academic, medievalist, literary critic, essayist, lay theologian and Christian apologist...
' Space Trilogy, and in particular in the first book entitled
Out of the Silent Planet__FORCETOC__Out of the Silent Planet is the first novel of a science fiction trilogy written by C. S. Lewis, sometimes referred to as the Space Trilogy, Ransom Trilogy or Cosmic Trilogy. The other volumes are Perelandra and That Hideous Strength, and a fragment of a sequel was published...
(1938). Three men, Weston, Devine and Ransom, set out for an interplanetary voyage from Earth to Mars (called
Malacandra in the narrative). Ransom, who had been brought along forcefully by Weston and Devine, in order to be handed over to the Sorns, succeeds in escaping after they have landed on the red planet, and thus comes to discover the geology, flora, fauna, and cultures present on Malacandra. He also discovers the relationship of planet Earth (called
Thulcandra, the
silent planet, in the narrative) with the other planets and forms of life present in the Solar System.
A comic figure of an intelligent Martian,
Marvin the MartianMarvin the Martian is a fictional character appearing in the Looney Tunes cartoons. Despite appearing in only five of the original shorts, Marvin has developed a cult following...
, appeared on television in 1948 as a character in the
Looney TunesLooney Tunes is a Warner Brothers animated cartoon series which ran in many movie theaters from 1930 to 1969. It preceded the Merrie Melodies series and is Warner Bros.'s first animated theatrical series. The regular Warner Bros...
animated cartoons of Warner Brothers, and has continued as part of popular culture to the present.
After the
MarinerThe Mariner program was a program conducted by the American space agency NASA that launched a series of robotic interplanetary probes designed to investigate Mars, Venus and Mercury...
and
VikingNASA's Viking program consisted of a pair of space probes sent to Mars, Viking 1 and Viking 2. Each vehicle was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...
spacecraft had returned pictures of Mars as it really is, an apparently lifeless and canal-less world, these ideas about Mars had to be abandoned and a vogue for accurate, realist depictions of human colonies on Mars developed, the best known of which may be
Kim Stanley RobinsonKim Stanley Robinson is an American science fiction writer known for his award-winning Mars trilogy. His work delves into ecological and sociological themes regularly, and many of his novels appear to be the direct result of his own scientific fascinations, such as the fifteen years of research...
's
Mars trilogyThe Mars trilogy is a series of award-winning science fiction novels by Kim Stanley Robinson that chronicle the settlement and terraforming of the planet Mars through the intensely personal and detailed viewpoints of a wide variety of characters spanning almost two centuries...
. However, pseudo-scientific speculations about the Face on Mars and other enigmatic landmarks spotted by
space probeA robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...
s have meant that ancient civilizations continue to be a popular theme in science fiction, especially in film.
Another popular theme, particularly among American writers, is the Martian colony that fights for independence from Earth. This is a major plot element in the novels of
Greg BearGregory Dale Bear is an American science fiction and mainstream author. His work has covered themes of galactic conflict , artificial universes , consciousness and cultural practices , and accelerated evolution .-Biography:Bear was...
and
Kim Stanley RobinsonKim Stanley Robinson is an American science fiction writer known for his award-winning Mars trilogy. His work delves into ecological and sociological themes regularly, and many of his novels appear to be the direct result of his own scientific fascinations, such as the fifteen years of research...
, as well as the movie
Total Recall (based on a short story by
Philip K. DickPhilip Kindred Dick was an American novelist, short story writer, and essayist whose published work during his lifetime was almost entirely in the science fiction genre. Dick explored sociological, political and metaphysical themes in novels dominated by monopolistic corporations, authoritarian...
) and the television series
Babylon 5Babylon 5 is an American science fiction television series created, produced and largely written by J. Michael Straczynski. The show centers on the Babylon 5 space station: a focal point for politics, diplomacy, and conflict during the years 2257–2262...
. Many video games also use this element, including
Red FactionRed Faction is a first-person shooter video game that was released in 2001 for the PlayStation 2, Microsoft Windows, and Macintosh by THQ and Volition. A version for the Nokia N-Gage was developed by Monkeystone Games. The game was also re-developed as a top-down shooter for the mobile phone.Red...
and the
Zone of the Enders, often abbreviated as Z.O.E., is a video game that was developed and published by Konami in 2001 for the PlayStation 2. It was produced by, and is closely associated with, Hideo Kojima. The game is based around mecha combat. The mechas were designed by Yoji Shinkawa, the character and mechanical...
series. Mars (and its moons) were also the setting for the popular
Doom video game franchise and the later
Martian GothicMartian Gothic: Unification is a survival horror game for the PlayStation and PC. It was developed by Creative Reality and published by Take-Two Interactive...
.
See also
- 2007 WD5
' is a diameter Apollo class Near-Earth object and a Mars-crosser asteroid discovered on November 20, 2007 by Andrea Boattini of the Catalina Sky Survey. Early observations of 2007 WD5 caused excitement amongst the scientific community when it was estimated as having as high as a 1 in...
– asteroid that had a possible impact with Mars on January 30, 2008
- Colonization of Mars
The colonization of Mars by humans is the focus of speculation and serious study, as the surface conditions and availability of water on Mars make it arguably the most hospitable planet in the solar system other than Earth...
- Darian calendar
The Darian Calendar is a proposed system of time-keeping designed to serve the needs of any possible future human settlers on the planet Mars. It was created by aerospace engineer and political scientist Thomas Gangale in 1985 and named by him after his son Darius.-Year length and intercalation:The...
– system of time-keeping
- Extraterrestrial life
Extraterrestrial life is defined as life which does not originate from planet Earth. The existence of life outside the planet is theoretical and all assertions of such life remain disputed....
- List of artificial objects on Mars
- List of chasmata on Mars
- List of craters on Mars
- List of valles on Mars
- Mars Direct
Mars Direct is a proposal for a relatively low-cost manned mission to Mars with current rocket technology. The plan was originally detailed in a research paper by Robert Zubrin and David Baker in 1990. The mission was expanded upon in Zubrin's 1996 book The Case for Mars...
- Mars Society
The Mars Society is an international space advocacy non-profit organization dedicated to encouraging the exploration and settlement of Mars. Founded by Robert Zubrin and others in mid-1998 and attracting the support of notable science fiction writers and filmmakers , the organization is dedicated...
- Terraforming of Mars
The terraforming of Mars is the hypothetical process by which the climate, surface, and known properties of Mars would be deliberately changed with the goal of making it habitable by humans and other terrestrial life, thus providing the possibility of safe and sustainable colonization of large...
External links
- 3D maps of Mars in NASA World Wind
- Google Mars – Interactive image of Mars
- Guide to Mars – information about Mars and how to observe it.
- Nine Planets Mars page
- On Mars: Exploration of the Red Planet 1958–1978 from the NASA History Office.
- Martian Law – a CATO white paper
- Computer Simulation of a flyby through Mariner Valley
- Mars Unearthed – Comparisons of terrains between Earth and Mars
- Ralph Aeschliman's Online Atlas of Mars
- Be on Mars – Anaglyphs from the Mars Rovers (3D)
- NASA/JPL OnMars WMS Server for Mars Data – Work as Google Earth client overlays
- Exploring Mars: Image Center
- Mars Astronomy Cast
Astronomy Cast is an educational nonprofit podcast discussing various topics in the field of astronomy. The specific subject matter of each episode shifts from week to week, ranging from planets and stars to cosmology and mythbusting...
episode #52, includes full transcript.
- Feb 07: ESA Prepares for a Human Mission to Mars
- Mars' apparent relative size at opposition as seen by HST
- Mars articles in Planetary Science Research Discoveries
- BBC News update on Mars Express' findings of polar water ice and water-eroded features on the surface
- BBC News Mars pictures reveal frozen sea
- Flight Into Mariner Valley – NASA/JPL/Arizona State University 3D flythrough of Valles Marineris
- Geody Mars – World's search engine that supports NASA World Wind
World Wind is a free, open source virtual globe developed by NASA and the open source community for use on personal computers. Old versions need Microsoft Windows but more recent Java versions are cross platform...
, CelestiaCelestia is a 3-D astronomy program created by Chris Laurel. The program is based on the Hipparcos Catalogue and allows users to travel through an extensive universe, modeled after reality, at any speed, in any direction and at any time in history...
, and other applications
- Mars Society – The Mars Society
The Mars Society is an international space advocacy non-profit organization dedicated to encouraging the exploration and settlement of Mars. Founded by Robert Zubrin and others in mid-1998 and attracting the support of notable science fiction writers and filmmakers , the organization is dedicated...
, an international organization dedicated to the study, exploration, and settlement of Mars.
Cartographic resources