Olympus Mons

Olympus Mons (Latin, "Mount Olympus") is the tallest known mountain in our solar system, located on the planet Mars at approximately . Before space probes revealed its identity as a mountain, Olympus Mons was known to astronomers as the albedo feature, Nix Olympica ("Snows of Olympus").

General description

The central edifice stands 25 kilometres (about 88,600 feet) high over its base (about three times the height of Mount Everest above sea level and 2.6 times the height of Mauna Kea above its base); it reaches 22 km (13 miles) above the mean surface level of Mars, since it stands in a 3 km (1.2 mile)-deep depression. It is 550 km (342 miles) in width, flanked by steep cliffs, and has a caldera that is 85 km (53 miles) long, 60 km (37 miles) wide, and up to 3 km (1.8 miles) deep with six overlapping pit craters. Its outer edge is defined by an escarpment up to 6 km (4 miles) tall unique among the shield volcanoes of Mars.

The size of Olympus Mons is so great (roughly the size of the American state of Arizona) that a person standing on the surface of Mars would be unable to view the profile of the volcano even from a distance as the curvature of the planet would obscure such detail. The only way to view the mountain properly is from orbit. Similarly, if one were to stand on the highest point of its summit, the slope of the volcano would extend all the way to the horizon.

An occasional misconception is that the top of Olympus Mons is above the Martian atmosphere. The atmospheric pressure at the top is about 2% that of average Martian surface pressure; by comparison the atmospheric pressure at the summit of Mount Everest is about 25% of that at sea level. Even so, airborne martian dust is still present and high altitude carbon dioxide-ice cloud cover is still possible at the peak of Olympus Mons, though water-ice clouds are not. Although the Martian average atmospheric pressure is less than 1% of that seen on Earth, the much lower gravity on Mars allows its atmosphere to extend much higher.

Two of the craters on Olympus Mons have been provisionally assigned names by the IAU. These are the 15.6 km diameter Karzok crater (18.4 N, 131.9 W) and the 10.4 km diameter Pangboche crater (17.2 N, 133.6 W).

Volcanism

Olympus Mons is a shield volcano, the result of highly fluid lava flowing out of volcanic vents over a long period of time, and is much wider than it is tall; the average slope of Olympus Mons' flanks is very gradual. In 2004 the Mars Express orbiter imaged lava flows on the flanks of Olympus Mons. Based on Base on crater size and frequency counts, the surface of this western scarp has been dated from 115 million years in age down to a region that is only 2 million years old. This is very recent in geological terms, suggesting that the mountain may yet have some ongoing volcanic activity.

The Hawaiian Islands are examples of similar shield volcanoes on a smaller scale (see Mauna Loa). The extraordinary size of Olympus Mons is likely due to the fact that Mars does not have tectonic plates. Thus, the crust remained fixed over a hot spot and continued to discharge lava, bringing the volcano to such a height.

The caldera at the peak of the volcano was formed after volcanism ceased and the roof of the emptied magma chamber collapsed. During the collapse the surface became extended and formed fractures. Later additional caldera collapses were formed due to subsequent lava production. These overlapped the original circular caldera, giving the edge a less symmetrical appearance.

Surroundings

Olympus Mons is located in the Tharsis bulge, a huge swelling in the Martian surface that bears numerous other large volcanic features. Among them are a chain of lesser shield volcanoes including Arsia Mons, Pavonis Mons and Ascraeus Mons, which are small only in comparison to Olympus Mons itself. The land immediately surrounding Olympus Mons is a depression in the bulge 2 km deep.

The volcano is surrounded by a region known as the Olympus Mons Aureole (Latin, "Circle of Light") with gigantic ridges and blocks extending 1000 km (600 miles) from the summit that show evidence of development and resurfacing connected with glacial activity. Both the escarpment and the Aureole are poorly understood. In one theory this basal cliff was formed by landslides and the Aureole consists of material piled up at the bottom of these landslides.

References

External links

Shield volcanoes | Volcanoes of Mars | Mountains on Mars

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General description

Volcanism

Surroundings

See also

References

External links