Arsia Mons

Arsia Mons

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Arsia Mons is the southernmost of three volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

s (collectively known as Tharsis Montes
Tharsis Montes
The 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...

) on the 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...

 bulge near the equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

 of the planet
A 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,...

Mars 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...

. To its north is Pavonis Mons
Pavonis Mons
Pavonis 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 north of that is Ascraeus Mons
Ascraeus Mons
Ascraeus 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 tallest mountain in the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

, Olympus Mons
Olympus Mons
Olympus Mons is a large volcanic mountain on the planet Mars. At a height of almost , it is one of the tallest mountains in the Solar System, three times as tall as Mount Everest and more than twice the height of Mauna Kea the tallest mountain on Earth. Olympus Mons is the youngest of the large...

, is to its northwest. Its name comes from a corresponding albedo feature
Albedo feature
An albedo feature is a large area on the surface of a planet which shows a contrast in brightness or darkness with adjacent areas....

 on a map by Giovanni Schiaparelli
Giovanni Schiaparelli
Giovanni 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...

, which he named in turn after the legendary Roman forest of Arsia Silva.

Arsia Mons is 270 miles (approximately 435 kilometres) in diameter, almost 12 miles high (more than 9 kilometres (5.6 mi) higher than the surrounding plains), and the summit caldera
A 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...

 is 72 miles (approximately 110 km) wide. It experiences atmospheric pressure
Atmosphere of Mars
The atmosphere of Mars is relatively thin and is composed mostly of carbon dioxide . There has been interest in studying its composition since the detection of trace amounts of methane, which may indicate the presence of life on Mars, but may also be produced by a geochemical process, volcanic or...

 lower than 107 pascals
Pascal (unit)
The 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...

 at the summit. Except for Olympus Mons, it is the biggest volcano in volume. Arsia Mons has 30 times the volume of Mauna Loa
Mauna Loa
Mauna Loa is one of five volcanoes that form the Island of Hawaii in the U.S. state of Hawaii in the Pacific Ocean, and the largest on Earth in terms of volume and area covered. It is an active shield volcano, with a volume estimated at approximately , although its peak is about lower than that...

 in Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, the largest volcano on the Earth.
A repeated weather phenomenon
Climate of Mars
The climate of Mars has been an issue of scientific curiosity for centuries, not least because Mars is the only terrestrial planet whose surface can be directly observed in detail from the Earth....

 occurs each year near the start of southern winter over Arsia Mons. Just before southern winter begins, sunlight warms the air on the slopes of the volcano. This air rises, bringing small amounts of dust with it. Eventually the rising air converges over the volcano's caldera and the fine sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

 blown up from the volcano's slopes coalesces into a spiraling cloud of dust that is thick enough to observe from orbit. The spiral dust cloud over Arsia Mons repeats each year, but observations and computer calculations indicate it can only form during a short period of time each year. Similar spiral clouds have not been seen over the other large Tharsis volcanoes, but other types of clouds have been seen. The spiral dust cloud over Arsia Mons can tower 15 to 30 kilometers (9 to 19 miles) above the volcano.

The caldera of Arsia Mons was formed when the mountain collapsed in on itself after its reservoir of magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 was exhausted. There are many other geologic collapse features on the mountain's flanks.

Possible Plate Tectonics

The three Tharsis Montes, together with some smaller volcanoes to the north, form a rather straight line. It has been proposed that these are the result of plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

, which on Earth makes chains of "hot spot" volcanoes.


Recent studies provide evidence for glaciers on Arsia Mons. A series of parallel ridges resemble moraines dropped by glaciers. Another section looks as if ice melted under the ground and formed a knobby terrain. A third bit of evidence is the lower part that has lobes and seems to be flowing onto the lower surface. This lobed feature probably still contains an ice core that is covered with a thin layer of rocks that keep the ice from sublimating.

Possible cave entrances

As of 2007 seven putative cave entrances have been identified in satellite imagery of the flanks of Arsia Mons. They have been informally dubbed Dena, Chloë, Wendy, Annie, Abbey, Nikki, and Jeanne and resemble "skylights" formed by the collapse of cave ceilings.

  • Dena (6.084°N 239.061°E)
  • Chloë (4.296°N 239.193°E)
  • Wendy (8.099°N 240.242°E)
  • Annie (6.267°N 240.005°E)
  • Abbey and Nikki (8.498°N 240.349°E)
  • Jeanne (5.636°N 241.259°E)

From day to night, temperatures of the circular features change only about one-third as much as the change in temperature of surrounding ground. While this is more variable than large caves on Earth, it is consistent with them being deep pits. However, due to the extreme altitude, it is unlikely that they will be able to harbour any form of Martian life
Life on Mars
Scientists have long speculated about the possibility of life on Mars owing to the planet's proximity and similarity to Earth. Fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries, but it remains an open question whether life currently exists on...


A more recent photograph of one of the features shows sunlight illuminating a side wall, suggesting that it may simply be a vertical pit rather than an entrance to a larger underground space. Nonetheless, the darkness of this feature implies that it must be at least 78 metres deep.

See also

  • Caves of Mars Project
    Caves of Mars Project
    The Caves of Mars Project was a program funded through Phase II by the NASA Institute for Advanced Conceptsto assess the best place to situate the research and habitation modules that a manned mission to Mars would require....

  • List of mountains on Mars by height
  • Tharsis quadrangle
    Tharsis quadrangle
    The 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 ....

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