NASA's Curiosity rover finds evidence of water below surface of Mars

Days after NASA's Curiosity rover said Mars must be holding glaciers beneath its dusty surface, the US space agency said on Monday the Red Planet has liquid water just below its surface, according to new measurements.

The Rover Environmental Monitoring Station (REMS) on NASA's Curiosity Mars rover includes temperature and humidity sensors mounted on the rover's mast. (Image: NASA/JPL-Caltech/MSSS)

Last week researchers at the Niels Bohr Institute in Copenhagen, Denmark, said Mars has huge glaciers of frozen water covered with thick layer of dust that appears as surface of the ground (See: Mars has frozen water beneath its dust cover, say Niels Bohr researchers).

Until now, scientists had thought that conditions on the red planet were too cold and arid for liquid water to exist, although there were known to be deposits of ice.

But, now, NASA's Curiosity rover has measured that Martian weather and soil conditions together with a type of salt found in Martian soil could put liquid brine in the soil at night.

Curiosity's latest findings suggest that Martian soil is damp with liquid brine, due to the presence of a salt that significantly lowers the freezing point of water. When mixed with calcium perchlorate liquid water can exist down to around -70 degree C, and the salt also soaks up water vapour from the atmosphere.

New measurements from the Gale crater show that during winter nights until just after sunrise, temperatures and humidity levels are just right for liquid brine to form.

''Perchlorate identified in Martian soil by the Curiosity mission, and previously by NASA's Phoenix Mars Lander mission, has properties of absorbing water vapor from the atmosphere and lowering the freezing temperature of water. This has been proposed for years as a mechanism for possible existence of transient liquid brines at higher latitudes on modern Mars, despite the Red Planet's cold and dry conditions.

''New calculations were based on more than a full Mars year of temperature and humidity measurements by Curiosity. They indicate 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. Conditions should be even more favorable at higher latitudes, where colder temperatures and more water vapor can result in higher relative humidity more often,'' NASA said in a release.

''The evidence so far is that any water would be in the form of permafrost. It's the first time we've had evidence of liquid water there now,'' Prof Andrew Coates, head of planetary science at the Mullard Space, said.

"We have not detected brines, but calculating the possibility that they might exist in Gale Crater during some nights testifies to the value of the round-the-clock and year-round measurements REMS is providing," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California, one of the new report's co-authors.

The chemical elements in water, hydrogen and oxygen, are some of the most abundant elements in the universe. Astronomers see the signature of water in giant molecular clouds between the stars, in disks of material that represent newborn planetary systems, and in the atmospheres of giant planets orbiting other stars (The Solar System and beyond is awash in water). 

Liquid water is traditionally considered an essential ingredient for life as we know it, but Mars remains hostile for other reasons. The latest findings are unlikely to change the view that if life ever blossomed on Mars, it probably died out more than a billion years ago, the scientists said.