{"id":18727,"date":"2017-11-20T23:40:32","date_gmt":"2017-11-20T15:40:32","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/trickles-of-water-on-mars-scientists-say-theyre-more-likely-to-be-trickles-of-sand\/"},"modified":"2017-11-20T23:40:32","modified_gmt":"2017-11-20T15:40:32","slug":"trickles-of-water-on-mars-scientists-say-theyre-more-likely-to-be-trickles-of-sand","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/trickles-of-water-on-mars-scientists-say-theyre-more-likely-to-be-trickles-of-sand\/","title":{"rendered":"Trickles of water on Mars? Scientists say they\u2019re more likely to be trickles of sand"},"content":{"rendered":"
\"Recurring
Recurring slope lineae appear as dark streaks in this picture from the HiRISE camera on NASA\u2019s Mars Reconnaissance Orbiter. (NASA \/ JPL \/ Univ. of Arizona \/ Lujendra Ojha et al. \/ Geophysical Research Letters)<\/figcaption><\/figure>\n

Scientists have long been intrigued by what seem to be wet streaks that appear on the slopes of Martian craters in warm weather, and disappear in winter. Now a research team reports that the best explanation is that they\u2019re not wet streaks at all, but streaks of dust and sand.<\/p>\n

The findings, published today in Nature Geoscience, are likely to disappoint those who hoped that the features known as recurring slope lineae, or RSLs, point to sources of liquid water beneath the Red Planet\u2019s surface.<\/p>\n

\u201cThis new understanding of RSL supports other evidence that shows that Mars today is very dry,\u201d study lead author Colin Dundas of the U.S. Geological Survey\u2019s Astrogeology Science Center said in a news release.<\/p>\n

Some astrobiologists had hoped that the areas around the RSLs just might harbor subsurface life. That\u2019s why NASA has said the thousands of potential RSL sites, including a smattering of prospects near the Curiosity rover, should be off-limits for the time being due to concerns about contamination.<\/p>\n

The report in Nature Geoscience is based on an analysis of 151 streaky features at 10 sites. Nearly all of the streaks appear on slopes that are steeper than 27 degrees, which would be consistent with the behavior of tumbling sand. If the streaks were caused by water seeping from the subsurface, they should be seen on slopes that are less steep, the researchers say.<\/p>\n

What\u2019s more, all of the streaks stop at a place matching the dynamic \u201cangle of repose\u201d that applies to sand dunes on Mars and on Earth.<\/p>\n

\u201cIt can\u2019t be a coincidence,\u201d said the University of Arizona\u2019s Alfred McEwen, the principal investigator for the High Resolution Imaging Science Experiment on NASA\u2019s Mars Reconnaissance Orbiter.<\/p>\n

So why do the streaks gradually appear starting in the spring, and fade away in the winter? Researchers suggest that hydrated salts in Martian soil might pull traces of water vapor out of Mars\u2019 thin atmosphere when the weather warms, triggering flows of sand. The darkening and lightening of the streaks could be linked to changes in hydration over the course of the Red Planet\u2019s seasons.<\/p>\n