Flowing water on Mars' surface may just be rolling sand instead
Source: The Verge
Flowing water on Mars' surface may just be rolling sand instead
by Loren Grush Nov 22, 2017, 11:05am EST
Two years ago, NASA made a big splash when it announced the discovery of flowing water on the surface of Mars. But it turns out, the space agency might have been wrong. The surface features that NASA thought were made up of liquid water may actually be flowing grains of sand instead, according to new research from the US Geological Survey. And that could decrease the chances of microbial life living on the Red Planet.
The features in question are dark streaks that show up periodically on Martian hills, known as recurring slope lineae, or RSLs. When one of NASA’s spacecraft, the Mars Reconnaissance Orbiter, studied these lines more closely, it found that the RSLs were made up of hydrated salts — meaning they were mixed with water molecules. At the time, NASA thought that was significant evidence that flowing liquid water caused these bizarre streaks.
But researchers at the USGS say these features look identical to certain types of slopes found on sand dunes here on Earth. Those slopes are caused by dry grains of sand flowing downhill, without the help of any water. It’s possible the same thing is happening on Mars, too. Since liquid water is key for life here on Earth, many thought these strange lines of flowing water may help support life on the Martian surface. But now these RSLs may not be the best place to look for life anymore.
Of course, it’s still possible that life could exist on Mars, but researchers may want to focus on other places, like under the surface. It’s thought that liquid water exists underground, where it’s a bit warmer and easier for water to stay a liquid. “Mars still has water now, it just might be in fewer accessible places,” Michael Meyer, the lead scientist for NASA’s Mars Exploration Program, tells The Verge.
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Read more: https://www.theverge.com/2017/11/22/16685278/nasa-mars-recurring-slope-lineae-liquid-water-sand
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Related: Previous Evidence of Water on Mars Now Identified as Grainflows (U.S. Geological Survey)
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Source: Nature Geoscience
Granular flows at recurring slope lineae on Mars indicate a limited role for liquid water
Colin M. Dundas, Alfred S. McEwen, Matthew Chojnacki, Moses P. Milazzo, Shane Byrne, Jim N. McElwaine & Anna Urso
Nature Geoscience (2017)
doi:10.1038/s41561-017-0012-5
Received: 10 January 2017
Accepted: 23 October 2017
Published online: 20 November 2017
Abstract
Recent liquid water flow on Mars has been proposed based on geomorphological features, such as gullies. Recurring slope lineae — seasonal flows that are darker than their surroundings — are candidate locations for seeping liquid water on Mars today, but their formation mechanism remains unclear. Topographical analysis shows that the terminal slopes of recurring slope lineae match the stopping angle for granular flows of cohesionless sand in active Martian aeolian dunes. In Eos Chasma, linea lengths vary widely and are longer where there are more extensive angle-of-repose slopes, inconsistent with models for water sources. These observations suggest that recurring slope lineae are granular flows. The preference for warm seasons and the detection of hydrated salts are consistent with some role for water in their initiation. However, liquid water volumes may be small or zero, alleviating planetary protection concerns about habitable environments.
https://www.nature.com/articles/s41561-017-0012-5
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