Olympus Mons is a large volcanic
mountainImage:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
on the planet
MarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
. At a height of almost 22 km (13.7 mi), it is one of the
tallest mountains in the Solar System, three times as tall as
Mount EverestMount Everest is the world's highest mountain, with a peak at above sea level. It is located in the Mahalangur section of the Himalayas. The international boundary runs across the precise summit point...
and more than twice the height of
Mauna KeaMauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
the tallest mountain on Earth. Olympus Mons is the youngest of the large volcanoes on Mars, having formed during Mars' Amazonian Period. Olympus Mons had been known to
astronomersAstronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
since the late 19th century as the
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....
Nix Olympica (Latin for "Snows of Olympus"). Its mountainous nature was suspected well before
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 confirmed its identity as a mountain.
The volcano is located in Mars' western hemisphere at approximately 18.4°N 226°E, just off the northwestern edge of the
TharsisThe Tharsis region on Mars is a vast volcanic plateau centered near the equator in Mars’ western hemisphere. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as...
bulge. The western portion of the volcano lies in the
Amazonis quadrangleThe Amazonis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Amazonis quadrangle is also referred to as MC-8 ....
(MC-8) and the central and eastern portions in the adjoining
Tharsis quadrangleThe Tharsis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey Astrogeology Research Program. The Tharsis quadrangle is also referred to as MC-9 ....
(MC-9). Two impact craters on Olympus Mons have been assigned provisional names by the
IAUThe International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
. They are the 15.6 km (10 mi)-
diameterIn geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
Karzok crater (18°25′N 131°55′W) and the 10.4 km (6 mi)-diameter Pangboche crater (17°10′N 133°35′W). The craters are notable for being two of several suspected source areas for shergottites, the most abundant class of Martian meteorites.
General description
Olympus Mons is a
shield volcanoA shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
, similar in morphology to the large volcanoes making up the
Hawaiian IslandsThe Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
. The edifice is about 600 km (372.8 mi) wide and stands nearly 22 km (13.7 mi) above the surrounding plains (a little over twice the height of
Mauna KeaMauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
as measured from its base on the ocean floor). The summit of the mountain has six nested
calderaA caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...
s (collapse craters) forming an irregular depression 60 × 80 km (37 × 50 mi) across and up to 3.2 km (2 mi) deep. The volcano's outer edge consists of an
escarpmentAn escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
, or cliff, up to 8 km (5 mi) tall, a feature unique among the
shield volcanoA shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
es of Mars. Olympus Mons covers an area approximately the size of
ArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
.
Being a shield volcano, Olympus Mons has a very low profile. The average slope on the volcano's flanks is only 5°. Slopes are highest near the middle part of the flanks and grow shallower toward the base, giving the flanks a
concaveThe word concave means curving in or hollowed inward, as opposed to convex. The former may be used in reference to:* Concave lens, a lens with inward-curving surfaces.* Concave polygon, a polygon which is not convex....
upward profile. The shape of Olympus Mons is distinctly asymmetrical. Its flanks are shallower and extend out further from the summit in the northwestern direction than they do to the southeast. The volcano's shape and profile have been likened to a "circus tent" held up by a single pole that is shifted off center.
Because of the size of Olympus Mons and its shallow slopes, an observer standing on the Martian surface would be unable to view the entire profile of the volcano, even from a great distance. The curvature of the planet and the volcano itself would obscure such a synoptic view. Similarly, an observer near the summit would be unaware of standing on a high mountain, as the slope of the volcano would extend beyond the horizon, a mere 3 kilometers away.
The typical atmospheric pressure at the top of Olympus Mons is 72
pascalThe pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
, about 12% of the average Martian surface pressure of 600 pascal. Both are exceedingly low by terrestrial standards. By comparison, the atmospheric pressure at the summit of
Mount EverestMount Everest is the world's highest mountain, with a peak at above sea level. It is located in the Mahalangur section of the Himalayas. The international boundary runs across the precise summit point...
is 32,000 pascals, or about 32% of Earth's sea level pressure. Even so, high-altitude
orographic cloudsOrographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions,...
are frequently observed over the Olympus Mons summit, and airborne Martian dust is still present. Although the average Martian surface atmospheric pressure is less than one percent of Earth's, the much lower gravity on Mars increases the atmosphere's
scale heightIn various scientific contexts, a scale height is a distance over which a quantity decreases by a factor of e...
; in other words, Mars' atmosphere is puffy and doesn't drop off in density with height as sharply as Earth's.
Olympus Mons is an unlikely landing location for automated space probes in the near future. The high elevations preclude parachute-assisted landings because of insufficient atmospheric thickness to slow the spacecraft down. Moreover, Olympus Mons is located in one of the dustiest regions of Mars. A mantle of fine dust covers much of the terrain, obscuring the underlying bedrock (rock samples might be hard to come by). The dust layer would also likely cause severe maneuvering problems for rovers.
Geology
Olympus Mons is the result of many thousands of highly fluid,
basalticBasalt 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...
lavaLava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
flows that poured from volcanic vents over a long period of time. (The
Hawaiian IslandsThe Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
exemplify similar shield volcanoes on a smaller scale - see
Mauna KeaMauna Kea is a volcano on the island of Hawaii. Standing above sea level, its peak is the highest point in the state of Hawaii. However, much of the mountain is under water; when measured from its oceanic base, Mauna Kea is over tall—significantly taller than Mount Everest...
.) The extraordinary size of Olympus Mons is likely because Mars lacks mobile
tectonic platesTectonic Plates is a 1992 independent Canadian film directed by Peter Mettler. Mettler also wrote the screenplay based on the play by Robert Lepage. The film stars Marie Gignac, Céline Bonnier and Robert Lepage.-Plot summary:...
. Unlike on Earth, the crust of Mars remains fixed over a stationary
hotspotThe places known as hotspots or hot spots in geology are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the mantle elsewhere. They may be on, near to, or far from tectonic plate boundaries. There are two hypotheses to explain them...
, and a volcano can continue to discharge lava until it reaches an enormous height.
The flanks of Olympus Mons are made up of innumerable lava flows and lava channels. Many of the flows have levees along their margins (pictured). Levees are parallel ridges formed at the edges of lava flows. The cooler, outer margins of the flow solidify, leaving a central trough of molten, flowing lava. Partially collapsed lava tubes are visible as chains of pit craters, and broad lava fans formed by lava emerging from intact, subsurface tubes are also common. In places along the volcano's base, lava flows can be seen spilling out into the surrounding plains, forming broad aprons, and burying the basal escarpment. (Note: Lava flows refer to both actively flowing lava and the solidified landforms they produce. The meaning here is the latter, since Mars has no active flows at the present time.) Crater counts from high resolution images taken by the
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...
orbiter in 2004 indicate that lava flows on the northwestern flank of Olympus Mons range in age from 115 million years old (Mya) to only 2 Mya. These ages are very recent in geological terms, suggesting that the mountain may still be volcanically active, though in a very quiescent and episodic fashion.
The caldera complex at the peak of the volcano is made of at least six overlapping calderas and caldera segments (pictured). Calderas are formed by roof collapse following depletion and withdrawal of the subsurface
magma chamberA magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...
after an eruption. Each caldera thus represents a separate pulse of volcanic activity on the mountain. The largest and oldest caldera segment appears to have formed as a single, large lava lake. The size of a caldera is a reflection of the size of the underlying magma chamber. Using geometric relationships of caldera dimensions from laboratory models, scientists have estimated that the magma chamber associated with the largest caldera on Olympus Mons lies at a depth of about 32 km below the caldera floor. Crater size-frequency distributions on the caldera floors indicate the calderas range in age from 350 Mya to about 150 Mya. All probably formed within 100 million years of each other.
Olympus Mons is asymmetrical
structurallyStructural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover information about the history of deformation in the rocks, and...
as well as
topographicallyTopography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
. The longer, more shallow northwestern flank displays extensional features, such as large slumps and normal faults. In contrast, the volcano's steeper southeastern side has features indicating compression. They include step-like terraces in the volcano's mid-flank region (interpreted as thrust faults) and a number of wrinkle ridges located at the basal escarpment. Why opposite sides of the mountain should show different styles of deformation is puzzling. The answer may lie in understanding how large shield volcanoes grow laterally and on how variations within the substrate of the volcano affect the final shape of the mountain.
Large shield volcanoes grow not only by adding material to their flanks as erupted lava, but also by spreading laterally at their bases. As a volcano grows in size, the stress field underneath the volcano changes from compressional to extensional. A subterranean rift may develop at the base of the volcano, causing the underlying crust to spread apart. If the volcano rests on sediments containing mechanically weak layers (e.g., beds of water-saturated clay), detachment zones (
decollementDécollement is a gliding plane between two rock masses. In French, "décoller" means "to detach from" or "to rip off" and was first used by geologists studying the structure of the Swiss Jura Mountains, but is also known as a detachment zone. This is a structure of strata owing to deformation,...
s) may develop in the weak layers. The extensional stresses in the detachment zones can produce giant landslides and normal faults on the volcano's flanks, leading to the formation of a basal escarpment. Further from the volcano, these detachment zones can express themselves as a succession of overlapping, gravity driven thrust faults. This mechanism has long been cited as an explanation of the Olympus Mons aureole deposits (discussed below).
Olympus Mons lies at the edge of the Tharsis bulge, a vast volcanic plateau that is very ancient. The formation of Tharsis was likely complete by the end of the Noachian Period. At the time Olympus Mons began to form in Hesperian times, the volcano was located on a shallow slope that descended from the high in Tharsis into the northern lowland basins. Over time, these basins would have received large volumes of sediment eroded from Tharsis and the southern highlands. The sediments likely contained abundant Noachian-aged phyllosilicates (clays) formed during a early period on Mars when surface water was abundant. The sediments would be thickest in the northwest where basin depth was greatest. As the volcano grew through lateral spreading, low-friction detachment zones preferentially developed in the thicker sediment layers to the northeast, creating the basal escarpment and widespread lobes of aureole material (
Lycus SulciLycus Sulci is a feature in the Amazonis quadrangle on Mars, with its location centered at 24.6° north latitude and 141.1° west longitude. It is 350 km long and is named after a classical albedo feature name....
). Spreading also occurred to the southeast; however, it was more constrained in that direction by the Tharsis rise, which presented a higher-friction zone at the volcano's base. Friction was higher in that direction because the sediments were thinner and probably consisted of coarser grained material resistant to sliding. The competent and rugged basement rocks of Tharsis acted as an additional source of friction. Thus, basal spreading of Mons Olympus was inhibited in the southeast direction, accounting for the structural and topographic asymmetry of the mountain. Numerical models of particle dynamics involving lateral differences in friction along the base of Olympus Mons have been shown to reproduce the volcano's present shape and asymmetry fairly well.
The detachment along the weak layers was likely aided by the presence of high-pressure water in the sediment pore spaces. This possibility has interesting astrobiological implications. If water-saturated zones still exist in sediments under the volcano, they would likely have been kept warm by a high geothermal gradient and residual heat from the volcano's magma chamber. Potential springs or seeps around the volcano would offer exciting possibilities for detecting microbial life.
Early observations and naming
Olympus Mons and a few other volcanoes in the Tharsis region stand high enough to reach above the frequent Martian dust-storms recorded by telescopic observers as early as the 19th century. The astronomer
Patrick MooreSir Patrick Alfred Caldwell-Moore, CBE, FRS, FRAS is a British amateur astronomer who has attained prominent status in astronomy as a writer, researcher, radio commentator and television presenter of the subject, and who is credited as having done more than any other person to raise the profile of...
points out that
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...
(1835-1910) "had found that his
Nodus Gordis and
Olympic Snow [Nix Olympica] were almost the only features to be seen" during dust storms, and "guessed correctly that they must be high". The
Mariner 9Mariner 9 was a NASA space orbiter that helped in the exploration of Mars and was part of the Mariner program. Mariner 9 was launched toward Mars on May 30, 1971 from Cape Canaveral Air Force Station and reached the planet on November 13 of the same year, becoming the first spacecraft to orbit...
spacecraft arrived in orbit around Mars in 1971 during a global dust-storm. The first objects to become visible as the dust began to settle, the tops of the Tharsis volcanoes, demonstrated that the altitude of these features greatly exceeded that of any mountain found on Earth, as astronomers expected. Afterward, astronomers adopted the name
Olympus Mons for the albedo feature known as Nix Olympica.
Regional setting and surrounding features
Olympus Mons is located at the northwestern edge of the
TharsisThe Tharsis region on Mars is a vast volcanic plateau centered near the equator in Mars’ western hemisphere. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as...
region, about 1200 km from the other three large Martian shield volcanoes, collectively called the
Tharsis MontesThe Tharsis Montes are three large shield volcanoes in the Tharsis region of the planet Mars. From north to south, the volcanoes are Ascraeus Mons, Pavonis Mons and Arsia Mons. Mons is the Latin word for mountain...
(
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...
,
Pavonis MonsPavonis Mons is a large shield volcano located in the Tharsis region of the planet Mars. It is the middle member of a chain of three volcanic mountains that straddle the Martian equator between longitudes 235°E and 259°E. The volcano was discovered by the Mariner 9 spacecraft in 1971 and was...
, and
Ascraeus MonsAscraeus Mons is a large shield volcano located in the Tharsis region of the planet Mars. It is the northernmost and tallest of three shield volcanoes collectively known as the Tharsis Montes. The volcano's location corresponds to the classical albedo feature Ascraeus Lacus.Ascraeus Mons was...
). The Tharsis Montes are slightly smaller than Olympus Mons.
A wide,
annularIn mathematics, an annulus is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. Or, it is the area between two concentric circles...
depression or
moatA moat is a deep, broad ditch, either dry or filled with water, that surrounds a castle, other building or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices...
about 2 km (1 mi) deep surrounds the base of Olympus Mons and is thought to be due to the volcano's immense weight pressing down on the Martian crust. The depth of this depression is greater on the northwest side of the mountain than on the southeast side.
Olympus Mons is partially surrounded by a region of distinctive grooved or corrugated terrain known as the Olympus Mons aureole. The aureole consists of several large lobes. Northwest of the volcano, the aureole extends a distance of up to 750 km and is known as
Lycus SulciLycus Sulci is a feature in the Amazonis quadrangle on Mars, with its location centered at 24.6° north latitude and 141.1° west longitude. It is 350 km long and is named after a classical albedo feature name....
(24.6° N, 219° E). East of Olympus Mons, the aureole is partially covered by lava flows, but where it is exposed it goes by different names (
Gigas SulciGigas Sulci is an area of subparallel furrows and ridges in the Tharsis quadrangle of Mars, located at . It is 398 km across and was named after a classical albedo feature name....
, for example). The origin of the aureole remains debated, but it was likely formed by huge landslides or gravity-driven
thrust sheetsA thrust fault is a type of fault, or break in the Earth's crust across which there has been relative movement, in which rocks of lower stratigraphic position are pushed up and over higher strata. They are often recognized because they place older rocks above younger...
that sloughed off the edges of the Olympus Mons shield.
See also
- List of mountains on Mars by height
- Volcanism on Mars
Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast volcanic plains, and the...
- Geology of Mars
The geology of Mars is the scientific study of the surface, crust, and interior of the planet Mars. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is fully analogous to the field of terrestrial geology. In planetary science, the term geology is...
- Tharsis
The Tharsis region on Mars is a vast volcanic plateau centered near the equator in Mars’ western hemisphere. The region is home to the largest volcanoes in the Solar System, including the three enormous shield volcanoes Arsia Mons, Pavonis Mons, and Ascraeus Mons, which are collectively known as...
plateau
External links