The discovery of water in the soils of Mars bodes well for potential future settlers, but don't pack your bags quite yet.
The results come from NASA's Mars rover Curiosity, which landed inside a giant impact basin in August 2012 to assess if the planet most like Earth in the solar system has or ever had the chemical ingredients and environments for life.
Its first analysis of fine-grained sand scooped up from the planet's surface revealed between 1.5 percent and 3 percent of water by weight.
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"If you take a cubic foot of that soil you can basically get two pints of water out it -- a couple of water bottles like you'd take to the gym, worth of water," Curiosity scientist Laurie Leshin, of Rensselaer Polytechnic Institute, N.Y., told Discovery News.
"It was kind of a surprise to me," she added.
Leshin and colleagues found the water -- along with sulfur dioxide, carbon dioxide, water and other gases -- by heating tiny bits of the soil inside Curiosity's onboard laboratory and analyzing released gases with science instruments.
The way the water was released indicates it likely was absorbed into the soil from the atmosphere, a telltale clue that water-laced soil is globally spread.
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"The water is not very well bound at all. You still have to sort of gently heat this stuff, but it comes off pretty easily," Leshin said.
"It's good news from the point of view of future of human space missions," added Curiosity lead scientist John Grotzinger, with the California Institute of Technology.
"It's also good news from the point of the view of microbes. If there's a chance for modern life on Mars, if there was a way that these fine materials could have been exploited to produce water, it might have helped in that sense," Grotzinger told Discovery News.
The analysis, however, also revealed a potential hazard in the soil -- perchlorates, which are known to impact human thyroid production of hormones.
"We would need to think about how we would mitigate any hazard from that," Leshin said.
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As a first step in developing technology to live off the Martian land, NASA is planning to include an experiment on its next rover that would pull carbon dioxide out of the atmosphere and purify it. Ultimately, the gas could be converted into oxygen for breathing and for propellant. The rover, which will be a copy of the Curiosity chassis and landing system, but with different science instruments, is targeted for launch in 2020.
Curiosity's analysis also showed no clear indigenous source for organic carbon found on Mars, though it did not rule out that possibility either.
The research appears in special report in this week's Science on the first 100 days of the Mars Curiosity mission.