Until now, scientists had thought that conditions on the red planet were too cold and arid for liquid water to exist, although there were known to be deposits of ice.
Professor Andrew Coates, head of planetary science at the Mullard Space Mullard Space Science Laboratory, University College London, said, “The evidence so far is that any water would be in the form of permafrost. It’s the first time we’ve had evidence of liquid water there now.”
The latest findings suggest that Martian soil is damp with liquid brine, due to the presence of a salt that significantly lowers the freezing point of water. When mixed with calcium perchlorate liquid water can exist down to around -70C and the salt also soaks up water vapour from the atmosphere.
New measurements from the Gale crater show that during winter nights until just after sunrise, temperatures and humidity levels are just right for liquid brine to form.
Morten Bo Madsen, a senior Mars scientist at the University of Copenhagen and a co-investigator on the Curiosity rover, said, “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.”
Liquid water is traditionally considered an essential ingredient for life as we know it, but Mars remains hostile for other reasons, the scientists said. The latest findings are unlikely to change the view that if life ever blossomed on Mars, it probably died out more than a billion years ago. “There are organisms on Earth, halophiles, that can survive in salty environments, but if it’s also very cold and very dry that’s a problem” said Madsen.
“The radiation on Mars nails it – that environment is very hostile.” Professor Coates agreed, “Liquid water is one of the conditions you need for life, it’s not all of them.”