Dirt sample reveals two pints of liquid water per cubic feet, not freely accessible but bound to other minerals in the soil.
Water has been discovered in the fine-grained soil on the surface of Mars, which could be a useful resource for future human missions to the red planet, according to measurements made by Nasa's Curiosity rover.
Each cubic foot of Martian soil contains around two pints of liquid water, though the molecules are not freely accessible, but rather bound to other minerals in the soil.
The Curiosity rover has been on Mars since August 2012, landing in an area near the equator of the planet known as Gale Crater. Its target is to circle and climb Mount Sharp, which lies at the centre of the crater, a five-kilometre-high mountain of layered rock that will help scientists unravel the history of the planet.
On Thursday Nasa scientists published a series of five papers in the journal Science, which detail the experiments carried out by the various scientific instruments aboard Curiosity in its first four months on the martian surface. Though highlights from the year-long mission have been released at conferences and Nasa press conferences, these are the first set of formal, peer-reviewed results from the Curiosity mission.
"We tend to think of Mars as this dry place – to find water fairly easy to get out of the soil at the surface was exciting to me," said Laurie Leshin, dean of science at Rensselaer Polytechnic Institute and lead author on the Science paper which confirmed the existence of water in the soil. "If you took about a cubic foot of the dirt and heated it up, you'd get a couple of pints of water out of that – a couple of water bottles' worth that you would take to the gym."
About 2% of the soil, by weight, was water. Curiosity made the measurement by scooping up a sample of the Martian dirt under its wheels, sieving it and dropping tiny samples into an oven in its belly, an instrument called Sample Analysis at Mars. "We heat [the soil] up to 835C and drive off all the volatiles and measure them," said Leshin. "We have a very sensitive way to sniff those and we can detect the water and other things that are released."