Brines may form from seasonal frost on Mars study finds

Brines may form from seasonal frost on Mars study finds
by Clarence Oxford
Los Angeles CA (SPX) Jul 22, 2025

Recent research led by Vincent Chevrier of the University of Arkansas offers new evidence that brines-salt-rich liquid water-could form on the Martian surface under specific seasonal conditions. Drawing on decades of research, Chevrier used atmospheric data from NASA's Viking 2 lander alongside advanced computer simulations to demonstrate that seasonal frost could briefly melt, creating small quantities of liquid brine.

According to Chevrier, Viking 2 remains the only mission to have definitively observed and analyzed surface frost on Mars. By merging this rare dataset with information from the Mars Climate Database, he identified a window in late winter to early spring when conditions may allow for brine formation-twice daily for a Martian month, particularly during early morning and late afternoon.

These brines would most likely form from calcium perchlorate, a salt known for its extremely low eutectic temperature of minus 75 degrees Celsius. Given that Mars' average equatorial temperature is around minus 50C, Chevrier's model indicates a narrow thermal window in which calcium perchlorate could temporarily exist as a liquid.

However, frost on Mars typically sublimates rapidly, bypassing the liquid state. Despite this, the study suggests that specific diurnal cycles may momentarily bring surface temperatures into the optimal range for brine formation.

Chevrier notes that any resulting liquid would be minimal, due to the thinness of Martian frost layers-less than a millimeter-and the relatively low concentration of calcium perchlorate in the regolith, estimated at only 1%.

Although the findings do not conclusively prove the existence of brines, they provide compelling support for transient liquid water in limited quantities. This has important implications for astrobiology, suggesting that Mars may occasionally host microenvironments suitable for life adapted to extreme cold and aridity.

Looking ahead, Chevrier advocates for robotic landers equipped with in situ hygrometers and chemical sensors to explore these seasonal windows. "The strong correlation between brine formation and seasonal frost cycles highlights specific periods when transient water activity is most likely, which could guide the planning of future astrobiological investigations," he concludes.

Research Report:Perchlorate brine formation from frost at the Viking 2 landing site