Martian anti-freeze makes liquid water possible

Data from NASA’s rover – Curiosity – has shown that liquid water could exist on Mars. A research team at the University of Copenhagen used soil data and discovered that a substance known as perchlorate – which lowers the freezing point of water – may indicate the presence of liquid water in a very salty state.

“We have discovered the substance calcium perchlorate in the soil and, under the right conditions, absorbs water vapour from the atmosphere. Our measurements from the Curiosity rover’s weather monitoring station show that these conditions exist at night and just after sunrise in the winter,” said Professor Morten Madsen, head of the Mars Group at the Niels Bohr Institute at the University of Copenhagen.

In the study, published in Nature, the scientists analysed the relative humidity, air temperature and ground temperature data from the Curiosity rover located at Gale Crater on Mars. They found that liquid water in very salty state – known as liquid brines – forms at night-time in the uppermost 5 cm of the subsurface and then evaporates after sunrise.

Madsen said: “When night falls, some of the water vapour in the atmosphere condenses on the planet surface as frost, but calcium perchlorate is very absorbent and it forms a brine with the water, so the freezing point is lowered and the frost can turn into a liquid. The soil is porous, so what we are seeing is that the water seeps down through the soil. Over time, other salts may also dissolve in the soil and now that they are liquid, they can move and precipitate elsewhere under the surface”.

Also, from close-up images the team recorded sedimentary deposits indicating that the entire Gale Crater may have been a lake.

“These kind of deposits are formed when large amounts of water flow down the slopes of the crater and these streams of water meet the stagnant water in the form of a lake,” added Madsen.

The researchers believe that liquid brines on the red planet are abundant beyond equatorial regions where atmospheric humidity is higher and temperatures are lower.