Planetary science: Martian surface brines common but not habitable

Liquid brines on Mars may be more common, and can last longer, than previously thought, suggests a paper published in Nature Astronomy. However, the study also suggests that the properties and temperatures of the brines make them inhospitable for Earth’s microorganisms.

Stable liquid water is unable to persist on the surface of Mars, as the planet’s atmosphere is too thin and cold. However, the presence of salts can create liquid substances, like brines, that can last stably for some time under Martian conditions.

Edgard Rivera-Valentín and colleagues combined an experimentally validated thermodynamic model with a climate model to investigate where brines could form on Mars and for how long. They found that up to 40% of the Martian surface, at all latitudes down to the equator, could host stable brines. These brines could last for up to six consecutive hours and during up to 2% of the entire Martian year. The authors also found that brines in the subsurface could last up to 10% of the Martian year at a depth of 8 cm.

The authors note that these brines cannot be classified as ‘Special Regions’ according to Planetary Protection policies, as they cannot sustain terrestrial life. The locations of the stable brines could be targets for future Martian exploration, since the risk of biological contamination from Earth is negligible.