Thursday, November 23, 2017

Flowing Water Marks on Mars Identified as Grainflows

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 According to a new study published in Nature Geoscience by the U.S. Geological Survey (USGS), dark features previously identified as liquid water flows on Mars have now been identified as flows of dust and sand. These new findings indicate that present-day Mars may not have significant volumes of liquid water on the surface to support the existence of Earth-like life.
 Scientists from the USGS, the University of Arizona, Durham University (England) and the Planetary Science Institute identified the dark, narrow surface features as Recurring Slope Lineae (RSL).  These RSL features grew and faded incrementally, recurring annually during the warmest time of the year on Mars.
 It was found with further analysis that the terminal ends of these RS slopes were identical to the slopes of sand dunes where movement was caused by dry granular flows. For water to cause these RSLs, the volume of water present would have to correspond to the length of slope available (needing more liquid on longer slopes). However, the similar slopes had very different lengths. Furthermore it was found that water was unlikely to be found near just the tops of the slopes with such defining angles.

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