Salty water might exist on Mars, but it’s probably too cold for life

Liquid brine can hang around on Mars’ surface, a new study suggests, but conditions may not be great for life as we know it.

That’s bad news for any Earth-based microorganisms determined to colonize the Red Planet, but good news for humans who don’t want to contaminate Mars with microbes hitching a ride on robot explorers.

Pure liquid water can’t last on Mars’ frigid surface. But mix in some salts, and H₂O might stick around for a bit. NASA’s Curiosity and Phoenix landers have detected salts known as perchlorates in the Martian soil, and researchers have suggested that such salts might make transient brines possible (SN: 3/20/09).

No salty liquid water has been definitively found on Mars. But there have been hints of water dribbling out from underground (SN: 9/28/15), and a controversial report of a buried lake near the Red Planet’s south pole (SN: 12/17/18).

To learn more about how brines would behave in contemporary Martian conditions, Edgard Rivera-Valentín, a planetary scientist at the Lunar and Planetary Institute in Houston, and colleagues ran computer simulations. They found that one type of brine could remain liquid on the planet’s surface and a few centimeters below for up to six consecutive hours across 40 percent of the planet, mostly at middle to high northern latitudes. However, those brines would never get warmer than about –48° Celsius, about 25 degrees below the known tolerance for life on Earth, the team reports online May 11 in Nature Astronomy.

This finding is useful for anyone planning a mission to Mars, the researchers say. Expeditions to locales with the potential for liquid water are subject to strict protection protocols (SN: 10/29/19) to reduce the risk of contamination from Earth. If Martian brines are truly uninhabitable by any known organism from our planet, that may ease restrictions on future exploration.