Melas Chasma is the deepest part of, for 10 points, what several kilometer deep valley along the Martian equator that dwarfs the Grand Canyon
Theories for its formation tend to explain it by invoking the lack of plate tectonics on Mars and rifting caused by the uplift of neighboring Tharsis, although whether water or carbon dioxide decompression possible caused by the Oudermans crater was the primary erosion mechanism is highly debated. Surveys indicate that it formed over former seafloor crust, and the Noctis Labyrinthus' jumbled terrain provides some of the best evidence for flooding. Melas Chasma is the deepest part of, for 10 points, what several kilometer deep valley along the Martian equator that dwarfs the Grand Canyon
Theories for its formation tend to explain it by invoking the lack of plate tectonics on Mars and rifting caused by the uplift of neighboring Tharsis, although whether water or carbon dioxide decompression possible caused by the Oudermans crater was the primary erosion mechanism is highly debated.
{Valles Marineris}