The latest data collected by US space agency NASA’s Curiosity rover has offered strong evidence for the existence of salty liquid water at the surface of Mars.

The Curiosity rover has discovered evidence of salty perchlorate compounds in the soil present on the Martian surface. According to the new findings, these compounds in the right conditions can absorb water vapour from the Martian atmosphere and reduce the freezing point of water. In simpler terms, liquid water present in the form of concentrated salt water (or brine) can form at the surface as well as at a few centimetres below it.

According to the scientists, the process is likely to take place only when the air available in the Martian environment is at its coldest. It means the favorable time would be at night or during winter mornings.

Morten Bo Madsen, a professor and a member of science team behind Curiosity rover project, said, “Perchlorates are not only oxidants, but they also form highly hygroscopic (water-absorbing) salts and are strong freezing-point depressors when added to water.”

After sunset, condensation of some water vapour begins on the surface of the planet as frost. The freezing point of the water is reduced with the absorption of perchlorates, like calcium perchlorate, in the soil. This will lead to turning the icy frost into a liquid. The soil is porous and this is the reason why the now-liquid water can soak down and precipitate elsewhere below the surface.

Morten Bo Madsen said, “This can explain salts mobility just below the surface, and with this research we now know that this can occur presently and hence is not just a relic from the past.”

The data were collected by Curiosity’s Sample Analysis at Mars (SAM), Rover Environmental Monitoring Station (REMS), and Dynamic Albedo of Neutrons (DAN) instruments. The data were gathered for over the period of a full Martian year (1.88 Earth years).

Concluding the findings, Torres said, “Generally, the study’s results have broad implications for the research works on the availability and the history of water on the Red Planet, for preserving plausible organic products, for studying the corrosive interaction of these brines with spacecraft materials, and, of course, for other geological processes related to water and climate on Mars today.”

The Curiosity instruments have offered the scientists with the largest ever environmental data recorded in-situ on Mars.

The findings of the new study have been detailed in the Journal Nature Geoscience.