Streaks on Mars are flowing sand, not water, study says
Photo provided by NASA's Jet Propulsion Laboratory at California Institute of Technology (JPL-Caltech), the University of Arizona (UA), and the United States Geological Survey (USGS), taken by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter (MRO) showing the inner slope of a crater on southern Mars with several of the seasonal dark streaks called "recurrent slope lineae," or RSL, that a November 2017 report interprets as granular flows, rather than darkening due to flowing water. EPA-EFE/NASA/JPL-Caltech/UA/USGS
Washington, Nov 20 (efe-epa).- A new interpretation of data obtained in 2011 by the Mars Reconnaissance Orbiter (MRO) concludes that what were initially considered to be the streaks caused by rivulets on Mars are really the marks of flowing sand, NASA reported Monday.
"Dark features on Mars previously considered evidence for subsurface flowing of water are interpreted by new research as granular flows, where grains of sand and dust slip downhill to make dark streaks, rather than the ground being darkened by seeping water," said NASA in a statement.
The conclusions of this new analysis, which was published in the scientific journal Nature Geoscience, appear to rule out the presence of flowing water - either above or below ground - on the Red Planet.
"We've thought of RSL (recurring slope lineae) as possible liquid water flows, but the slopes are more like what we expect for dry sand," said Colin Dundas of the US Geological Survey's Astrogeology Science Center in Flagstaff, Arizona.
"This new understanding of RSL supports other evidence that shows that Mars today is very dry," he added.
The new interpretation of the data thus means that there is not enough liquid water on Mars to create rivulets that could have caused the streaks.
Thousands of these streaks, called "intermittent flows" because they appear only during the planet's warmest season, have been detected in more than 50 areas on the planet's surface, thus initially raising hopes about the presence of free-flowing water there and leading NASA in 2015 to say it had evidence of water on Mars.
Using the spectrometer on the MRO space probe, scientists at that time detected signs of hydrated minerals on the slopes of Martian mountains where they also found the mysterious streaks.
The color of the streaks darkens during the Martian summer, thus seemingly corroborating the idea of water trickling down the sides of the slopes.