Washington, Nov 22 (PTI) Dark features on Mars, that werethought to be evidence of liquid water flowing on the redplanet, were created by moving sand and dust, a studysuggests.
The findings indicate that present-day Mars may not havea significant volume of liquid water. The water-restrictedconditions that exist on Mars would make it difficult forEarth-like life to exist near the surface of the planet.
Scientists, including those from the University ofArizona in the US and Durham University in the UK analysednarrow, down-slope trending surface features on Mars that aredarker than their surroundings, called Recurring Slope Linea(RSL).
These RSL features grow incrementally, fade when inactiveand recur annually during the warmest time of year on Mars.
RSL are mostly found on steep rocky slopes in darkregions of Mars, such as the southern mid-latitudes, VallesMarineris near the equator, and in Acidalia Planitia on thenorthern plains.
The appearance and growth of these features resembleseeping liquid water, but how they form remains unclear, andthis research demonstrated that the RSL flows seen by HiRISEare likely moving granular material like sand and dust.
"We've thought of RSL as possible liquid water flows, butthe slopes are more like what we expect for dry sand," saidColin Dundas, scientist at US Geological Survey.
"This new understanding of RSL supports other evidencethat shows that Mars today is very dry," said Dundas, leadauthor of the study published in the journal NatureGeoscience.
The terminal end of the RSL slopes are identical to theslopes of sand dunes where movement is caused by dry granularflows, he said.
Water almost certainly is not responsible for thisbehaviour, which would require the volume of liquid tocorrespond to the length of slope available, producing moreliquid on longer slopes.
Instead, the 151 RSL examined by the study authors allend on similar slopes despite very different lengths.
According to the scientists, water is unlikely to beproduced only near the tops of slopes at these angles and ifit were, it should be able to flow onto lower slopes.
This new research finds that these RSL features are flowsof granular material and thus, align with the long-standinghypothesis that the surface of Mars lacks flowing water.
Small amounts of water could still be involved in theirinitiation in some fashion, as hydrated minerals have beendetected at some RSL locations.
Researchers conclude that liquid on present-day Mars maybe limited to traces of dissolved moisture from the atmosphereand thin films of water. PTI MHN SARMHN.
This is unedited, unformatted feed from the Press Trust of India wire.