A new NASA study suggests if life ever existed on Mars, the place where it was most likely was just below the surface of the planet.
A new twist of years of data, that were collected from more than 350 sites on Mars by European and NASA orbiters, suggests Mars had abundant liquid water on the surface only briefly. These short periods occurred toward the end of hundreds of millions of years during which warm water interacted with subsurface rocks. This has implications about where and when life may have existed on Mars and how its atmosphere has changed over time.
Discovery of clay minerals in rocks several years ago indicated the planet once was warmer and wetter. If those conditions existed on the surface for longer, the planet would have needed a much thicker
atmosphere as compared to what it has now to keep the water from evaporating or freezing. Researchers have sought reasons to explain why the atmosphere may have eroded.
A new study supports an alternative hypothesis in which persistent warm water was confined only to the subsurface and many erosional features were carved during short periods when water was found at the surface.
During the past five years, researchers used OMEGA and NASA's Compact Reconnaissance Imaging Spectrometer, or CRISM, instrument on the Mars Reconnaissance Orbiter to identify clay minerals at thousands of locations on Mars. Clay minerals that form where the ratio of water interacting with rock is low generally retain the same chemical elements as the original volcanic rocks later changed by the water.
The study interprets this to be the case for most terrains on Mars with iron and magnesium clays, so the amount of water on the surface of Mars was likely small and also short-lived. Thus the atmosphere in the past may have been thicker as well.
NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, in development for a 2013 launch, may provide evidence for or against this new interpretation of the Red Planet's environmental history. The report predicts MAVEN's findings consistent with the atmosphere not having been thick enough to provide warm, wet surface conditions for a long period.
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