NASA’s Curiosity rover, which has been exploring the Martian surface since August 2012, has detected planetary conditions that suggest the presence of a transient “liquid brine” that appears on the surface at nighttime. This is a big finding for Curiosity, a main goal of which has been to investigate the role of water in the history of microbial life in Mars’s Gale Crater. Curiosity’s findings are the result of over a year (that’s a Martian year – 687 days) of measuring the planet’s temperature and humidity levels.
Water has long been known to exist on Mars in the form of polar ice caps, but data has never hinted so strongly at its presence in a liquid state. What’s more, its probable appearance in an unlikely place suggests that this is a more pervasive phenomenon on Mars than previously thought. In turn, this may have implications for the search for microbial life on the Red Planet.
How transient brines might be appearing on Mars at night
The process, as scientists have proposed, begins with perchlorate, a type of salt that is prevalent in the Martian soil. Certain microbial life forms on earth use perchlorate as an energy source, but the reactive chemical is toxic to humans. When humidity levels on the Martian surface are high enough, the perchlorate salts in the soil can absorb enough water molecules that the salts are dissolved in a solution commonly referred to as a brine.
Still, the possible existence of such a brine near Mars’s equator may not be cause for excitement. Javier Martin-Torres, the lead author of the study containing the findings, downplayed the possibility that the brines near the equator would yield any earth-shattering findings, but he characterized it as a positive development nonetheless:
“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 process.”
Those keeping a close eye on future Mars missions, including the Mars One colonization project and NASA’s Asteroid Redirect Mission, might be especially interested in the habitability implications of Curiosity’s findings.
The brines may be more prevalent than previously believed
According to the report from NASA’s Jet Propulsion Laboratory, scientists have proposed for several years that such a brine may exist in this form, but never have they had such hard evidence. However, they have hypothesized the brine’s existence at much higher latitudes, so its presence in the Gale Crater suggests it may be much more prevalent elsewhere.
Alfred McEwan, also an author of the report, studies a phenomenon on Mars known as recurring slope linae (RSL), whereby dark flows appear at numerous locations on the Martian surface during warmer periods of the year. According to the JPL release, the brine-forming process described above is a part of the “leading hypothesis” for how RSL occur. McEwan is also among those who think the possibility of brines near the Martian equator is something to get excited about:
“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. So if brines can exist there, that strengthens the case they could form and persist even longer at many other locations, perhaps enough to explain RSL activity.”
See this video for more on how Curiosity makes its discoveries about Mars’s history and geography: