Liquid Water Remains on Mars Today, Rover Hints

No, Mars is not home to the massive ocean it once held. These days, most of its water is locked up in glaciers and large ice caps. Now, however, researchers think they have found signs that there is still some liquid water in the planet's soil, after finding evidence for liquid brine with NASA's Curiosity rover.

"Liquid water is a requirement for life as we know it, and a target for Mars exploration missions," Javier Martin-Torres of the Spanish Research Council, Spain, and Lulea University of Technology, Sweden, said in a statement. "Conditions near the surface of present-day Mars are hardly favorable for microbial life as we know it, but the possibility for liquid brines on Mars has wider implications for habitability and geological water-related processes."

Martin-Torres, a member of the Curiosity mission team, recently helped publish a new paper in the journal Nature Geosciences that considers more than a full Martian year (1.88 Earth years) of temperature and humidity measurements made by the rover - which began its scientific mission on the Red Planet in 2012.

New calculations based around that data show that conditions at the rover's near-equatorial location were favorable for small quantities of brine to form during some nights throughout the year, drying out again after sunrise. This would explain why the water has remained elusive and undetectable during Curiosity's solar powered missions.

"Gale Crater is one of the least likely places on Mars to have conditions for brines to form, compared to sites at higher latitudes or with more shading," added co-author Alfred McEwen, of the University of Arizona, Tucson. "So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations."

McEwen noted that enough of this disappearing brine could even explain for unusual geographic features, called recurring slope lineae (RSL). These appear as dark flows that can be observed on slopes during Martian warm seasons, but have not been personally seen by Curiosity. Instead, they have been highlighted by experts using the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter.

The rover's team now hopes that conditions for detecting this brine-building phenomenon will be more favorable as Curiosity climbs to higher altitudes. Currently, the unmanned robot is not far from Mars' upper Mount Sharp.

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