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.