Previous discoveries by Curiosity and Opportunity have already established that liquid water may have flowed in abundance on the planet in the distant past.
Far from the cold and dry desert that the planet currently displays, Mars could have proposed vast oceans and rivers which have dug canyons like bloodlings on its surface during a few million years.
Despite everything, a new discovery relaunches the hypothesis that we can find water in liquid form on Mars today.
"We discovered calcium perchlorate in the soil (…), a substance which under certain conditions absorbs water vapor present in the atmosphere" says Morten Bo Madsen, co-author of the work which benefits from a publication in the scientific journal Nature.
Perchlorate is a type of salt that lowers the freezing point of water and allows it to stay in its liquid form despite a negative temperature.
At nightfall, part of the water vapor in the atmosphere condenses on the surface of the planet. The calcium perchlorate present on the surface would be able to absorb this water and create a kind of "brine". The planet's soil being porous, water would infiltrate it almost instantly, leaving only a small chance of finding this type of puddle without digging.
The study of the different strata of the Mars crust around Mount Sharp has also highlighted the formation of sedimentary deposits, which only form when large quantities of water flow along the crater.
Most of the water formerly present on Mars would have evaporated in space when the planet lost its magnetic field and its atmosphere became lighter.
But if we came to find liquid water on Mars, this does not mean that we will find a form of life there: "Even if water in liquid form exists on Mars, it is unlikely that life will be found on Mars." The environment is "too dry, too cold and undergoes such powerful cosmic radiation that it penetrates at least a meter below the surface, killing all life."