Zee Media Bureau
Washington: NASA scientists studying Mars have given convincing clues that possible liquid water may still exist on the surface of Mars even today in the form of ice.
NASA`s Mars Reconnaissance Orbiter and Odyssey orbiter have sent back new images that show streaks that appear and disappear on the surface of the Red Planet.
Researchers call these dark flows “recurring slope lineae” (RSL). RSL emanate from bedrock exposures at Palikir crater on Mars during southern summer.
These flows are observed to form and grow during warm seasons and fade or completely disappear in cold season.
"We still don`t have a smoking gun for existence of water in RSL, although we`re not sure how this process would take place without water," said Lujendra Ojha, lead author of two reports published in the journals Geophysical Research Letters and Icarus.
Although the team did not find any spectral signature tied to water or salts, they did find distinct and consistent spectral signatures of ferric and ferrous minerals at most of the confirmed RSL sites.
The researchers said these iron-bearing minerals were more abundant or featured distinct grain sizes in RSL-related materials as compared to non-RSL slopes.
One possible explanation for these changes is a sorting of grain sizes, such as removal of fine dust from the surface, which could result from either a wet process or dry one, the researchers said.
Other explanations could be an increase in the more-oxidized component of the minerals, or an overall darkening due to moisture. Either of these would point to water, even though no water was directly detected, they noted.
The researchers also compared new observations with images from previous years, revealing that RSL are much more abundant some years than others.
(With Agency inputs)