Olympus Mons, tallest mountain on Mars in the Solar System
Olympus Mons (Latin for "Mount Olympus") is a mountain which is located on the planet Mars at approximately 18°24′N 226°00′E / 18.4°N 226°E / 18.4; 226. It is a little under three times as tall as Mount Everest, and is in fact the tallest known volcano and mountain in the Solar System. Olympus Mons was formed during Mars' Amazonian epoch. Since the late 19th century — well before space probes confirmed its identity as a mountain — Olympus Mons was known to astronomers as the albedo feature Nix Olympica (Latin for "Snows of Olympus"), although its mountainous nature was suspected.
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 old lava flows on the flanks of Olympus Mons. Based on crater size and frequency counts, the surface of this western scarp has been dated from 115 million years old 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 Kea). The extraordinary size of Olympus Mons is likely because Mars does not have tectonic plates. Thus, the crust remained fixed over a hotspot and the volcano continued to discharge lava, until it reached 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. Additional caldera collapses were formed later due to subsequent lava production. These overlapped the original circular caldera, giving the edge a less symmetric appearance.
Early observations and namingEdit
The mountain, as well as a few other of the volcanoes in the Tharsis region, has sufficient height to reach above the frequent Martian dust storms, and that was visible from Earth already to 19th century observers. The astronomer Patrick Moore points out that during dust storms, "Schiaparelli had found that his Nodus Gordis and Olympic Snow were almost the only features to be seen. He guessed correctly that they must be high". Only with the Mariner probes could this be confirmed with certainty. After the Mariner 9 probe had photographed it from orbit in 1972, it became clear that the altitude was much greater than that of any mountain found on Earth, and the name was changed to Olympus Mons.
Caldera and pit craters on Olympus Mons. Olympus Mons is located in the Tharsis region, a huge swelling in the Martian surface that bears numerous other large volcanic features. Among them are a chain of lesser shield volcanoes called the Tharsis Montes—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 (1 mi) deep.
The volcano is surrounded by a region known as the Olympus Mons aureole (Latin, "circle of light") with gigantic ridges and blocks extending 1,000 km (621 mi) 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 basalt cliff was formed by landslides, and the aureole consists of material they deposited. A view of this escarpment (scarp/cliff) is shown in the picture taken by HiRISE below. From Wikipedia, the free encyclopedia