NASA scientists say they have found new evidence that a groundwater-fed lake may have existed in an Mars crater that adds to the increasingly complex picture of the Red Planet's early evolution.
The new findings published in Sunday's online edition of Nature Geoscience, were obtained from analysis of spectrometer data from NASA's Mars Reconnaissance Orbiter (MRO) of the McLaughlin Crater.
The Martian crater, which is 57 miles in diameter and 1.4 miles deep, was found to have contained layered, flat rocks at its bottom that contain carbonate and clay minerals which only form in the presence of water, according to NASA.
The crater lacks large inflow channels, and small channels originating within the crater wall end near a level that could have marked the surface of a lake, said scientists.
"Taken together, the observations in McLaughlin Crater provide the best evidence for carbonate forming within a lake environment instead of being washed into a crater from outside," said Joseph Michalski, lead author of the paper.
Michalski and his co-authors used the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on MRO to check for minerals such as carbonates, which are best preserved under non-acidic conditions.
"A number of studies using CRISM data have shown rocks exhumed from the subsurface by meteor impact were altered early in Martian history, most likely by hydrothermal fluids," Michalski said.
"These fluids trapped in the subsurface could have periodically breached the surface in deep basins such as McLaughlin Crater, possibly carrying clues to subsurface habitability," he added.
McLaughlin Crater sits at the low end of a regional slope several hundreds of miles long on the western side of the Arabia Terra region of Mars.
As on Earth, groundwater-fed lakes are expected to occur at low regional elevations. Therefore, this site would be a good candidate for such a process.
"This new report and others are continuing to reveal a more complex Mars than previously appreciated, with at least some areas more likely to reveal signs of ancient life than others," said MRO project scientist Rich Zurek of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
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