NASA's Mars Orbiters Find Clues to Seasonal Water Flow on Martian Surface

NASA says the Mars orbiters have returned with significant clues indicating the presence of free flowing water on the Martian surface.

The two spacecrafts, Mars Reconnaissance Orbiter (MRO) and  Mars Odyssey, offer clues about the seasonal features of the Red planet and which are the strongest indication that  liquid water may exist on Mars.

The indication of the presence of free flowing water comes from the seasonal dark flows also called the recurring slope lineae (RSL).  The agency says there are dark finger-like markings that appear to flow down the Martian mountains as the temperature on the surface rises. 

As reported in Forbes, scientists examining the Martian environment believe that these dark flows are triggered by saltwater that contain iron sulphate solution preventing the water from freezing in the Martian temperatures. Though it isn't clear whether RSL is due to the seasonal liquid flow during the summer, but images captured by MRO reveal that the RSL does have flowing water.

"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, a graduate student at the Georgia Institute of Technology, Atlanta, and lead author of two reports about these flows

These RSL on the Martian surface, currently a popular acronym discussed among Mars scientists, were basically discovered three years ago by Ojha in a high Resolution Imaging Science Experiment (HiRISE) camera mounted on MRO.

Ojha along with his colleagues focused on 13 confirmed RSL sites with the help of the images captured from MRO's HiRISE camera and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). Though the images didn't reveal any signs of salt or water but they show traces of iron containing minerals that were not present on the Martian slopes that lacked RSL. The presence of these minerals changes along with the seasons. The iron containing minerals increased during the warmer climate and in winters the presence of the spectral signature dropped.

An explanation of these RSL flows and seasonal changes in minerals involves water. Other explanation could be moisture, which darkens the flow, and oxidizing of these minerals adding to its iron components.

The presence of near-surface water adds to the theory of water on Mars and scientists say that the presence of salt prevents it from freezing.

 "The flow of water, even briny water, anywhere on Mars today would be a major discovery, impacting our understanding of present climate change on Mars and possibly indicating potential habitats for life near the surface on modern Mars," said Mars Reconnaissance Orbiter Project Scientist Richard Zurek, of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

They team found other ideal sites for RSL formations near the southern mid latitudes on rocky cliffs. But just 13 out of the 200 sites confirmed the presence of RSL. The fact that RSL can be seen only on few sites and not everywhere, strongly hints that certain unknown factors such as water or salts play a significant role in the formation of RSL. On comparing the new observations with images captured in previous years, it was seen that RSL was more abundant a few years ago.

"NASA likes to 'follow the water' in exploring the Red Planet, so we'd like to know in advance when and where it will appear," Georgia Tech assistant professor James Wray. "RSL have rekindled our hope of accessing modern water, but forecasting wet conditions remains a challenge."

The study was published in the journal Geophysical Research Letters.