There is good evidence in the form of observable river deltas, and the most recent measurements made on the surface of Mars suggest that liquid water flowed on Mars billions of years ago.
Mars likely has less water in the form of brine, salt-water mixtures that are more resistant to boiling, freezing, and evaporation.
Scientists at the Arkansas Center for Space and Planetary Sciences suggest that Mars has even less liquid water than previously thought. The scientists conclude by studying combined data on the evaporation rates of brine with a model of the planet’s global meteorological circulation.
The combined data allowed them to create planetary maps of where brines are most likely to be found.
All significant phase changes of the liquids (freezing, boiling, and evaporation) were taken into account to observe all properties simultaneously, rather than one at a time. Then they built a map taking into account all those processes simultaneously.
Vincent Chevrier, associate professor and first author of a study published in the Planetary Science Journal, said: “Doing so indicates that previous studies may have overestimated how long brines remain on the surface in the cold, thin and arid Martian atmosphere. The most important conclusion is that if all these processes are not taken together, the stability of the brines is always overestimated. That is the reality of the situation. “
“Favorable conditions for stable brines are more likely to exist on the planet’s surface in northern mid- and high-latitudes and in high-impact craters in the southern hemisphere. In the shallow subsoil, there may be brines near the equator. “
“In the best of cases, the brines could be present for up to 12 hours a day. Nowhere is there a stable brine for a whole day on Mars. “
Magazine reference:
- Vincent F. Chevrier et al. Global temporal and geographic stability of brines on current Mars, The Planetary Science Journal (2020). DOI: 10.3847 / PSJ / abbc14