Valles Marineris

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Valles Marineris (Latin for Mariner Valleys, named after the Mariner 9 Mars orbiter of 1971–72 which discovered it) is a system that runs along the Martian surface east of the Tharsis region. At more than 4,000 km long, 200 km wide and up to 7 km deep,[1][2] the Valles Marineris rift system is the largest known canyon, surpassing all canyons on Earth.

Valles Marineris is located along the equator of Mars, on the east side of the Tharsis Bulge, and stretches for nearly a quarter of the planet’s circumference. The Valles Marineris system starts in the west with the Noctis Labyrinthus; proceeding to the east are Tithonium and Ius chasmata, then Melas and Ophir chasmata, then Coprates Chasma, then Ganges, Capri and Eos chasmata; finally it empties into an outflow channel region containing chaotic terrain that ends in the basin of Chryse Planitia. Most researchers agree that Valles Marineris is a large tectonic "crack" in the Martian crust that formed as the crust rose in the Tharsis region to the west, and was subsequently widened by erosional forces. However, near the eastern flanks of the rift there appear to be some channels that may have been formed by water or carbon dioxide.



There have been many different theories about the formation of Valles Marineris that have changed over the years. Ideas in the 1970s were erosion by water or thermokarst activity, which is the melting of permafrost in glacial climes. Thermokarst activity may contribute, but erosion by water is not very likely because liquid water cannot exist in most current Martian surface conditions, which typically experience about 1% earth’s atmospheric pressure and a temperature range of 148 to 310 kelvins.However, scientists agree that there was liquid water flowing on the Martian surface in the past. Valles Marineris may have been formed by flowing water at this time. Another hypothesis by McCauley in 1972 was that the canyons formed by withdrawal of subsurface magma. Around 1989 Tanaka and Golombek proposed a theory of formation by tensional fracturing. The most agreed upon theory today is that Valles Marineris was formed by rift faults like the East African Rift Valley, later made bigger by erosion and collapsing of the rift walls. One source of this erosion, proposed by Nick Hoffman is decompression of the Noctis Labyrinthus carbon dioxide aquifer. As carbon dioxide is decompressed it turns from a solid to a fluid/gas and can travel at great velocities through the thin atmosphere of Mars.

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