The new observations by rovers and orbiters indicate that liquid water exists on Mars, and covered large parts of the planet's surface for more than a billion year in the past. It was determined that the deposits were hydrated sulfate minerals, rich in iron and magnesium, concentrated just below the dusty surface. These landforms included enormous channels carved by catastrophic floods and large scale valley networks that is reminiscent of river drainage systems on Earth. Additional evidence of an Earth-like climate in Mars's past comes from high resolution images that were taken by Mars Odyssey and Global Surveyor orbiters of the small scale valley networks on the plateaus and walls of the Valles Marineris canyn system. Newly found networks have characteristics that are consistent with their formation by rainfall or snowmelt and surface runoff. Future mission to Mars may test the hypothesis by measuring the ages of ancient landforms.
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