TORONTO - A mysterious white substance churned out of the Martian dust by the wheels of the Spirit rover is the first "on-the-spot" evidence of water beneath the surface of the Red Planet, researchers at a Canadian university declared Wednesday.
As scientists around the world work to determine if the basic requirement for life exists on Mars, the first solid evidence based on soil samples "clicks" with earlier satellite data suggesting the presence of water, said University of Guelph physicist Iain Campbell.
"All this other geological evidence says, there really should be some water here," Campbell said.
"Then we come along and say, 'Hey, we think we found some water here,' and the last thing clicks into place."
The white, salty substance that forms the basis of the university's findings was kicked up by the rover's wheels in the Columbia Hills region of the planet, near the equator.
Campbell's team used X-ray analysis transmitted back to earth by Spirit to conclude that the samples, most likely the remnants of oceans or pools that evaporated, contain up to 16 per cent water.
"This is on-the-spot. We're looking, for the first time, with an instrument on the surface . . . at soil that's been churned up by the rover wheels," Campbell said.
"We're seeing indirect evidence of water, water that's chemically bound into a white, salty stuff that seems to lie below the surface sand."
The research, which is under review by the Journal of Geophysical Research, is based on four samples taken from various locations within the Columbia Hills.
As for how widespread those concentrations of water might be, Campbell said he couldn't speculate.
"What we'd very much like is if the rover would go back there and take some more," said Campbell, who added that's unlikely, given the demands placed on the two Mars rovers.
The Spirit was launched in June 2003 and landed on the Martian surface the following January. A second rover, christened Opportunity, touched down on the opposite side of the planet later the same month.
Both were given a shelf life of 90 days.
More than 3 1/2 years later and on borrowed time, the two 180-kilogram robots are still roaming the planet. They've transmitted almost 200,000 images of Martian terrain and microscopic images of rocks and soil surfaces back to Earth.
John Rummel, a senior scientist with NASA's astrobiology department, said Mars exploration is primarily focused on "where water is today and how what we see can tell us about the availability of water on Mars in the distant past."
"Only by solving that puzzle can we also focus our search for life, past or present, and understand how the habitability of Mars continues to evolve."
Assisting the search from high above the planet is NASA's Mars Reconnaissance Orbiter. Its camera, the most powerful ever used in a planetary exploration mission, has provided images showing alternating layers of dark- and light-toned rock in a giant rift valley.
In February, University of Arizona researchers said those images suggest evidence of water passing through bedrock.
Last year, scientists reported that images from the Mars Global Surveyor provided evidence that water may have moved through craters on the Red Planet as recently as several years ago.
"So you have lots of bits of evidence . . . that conspire to say you had quite a lot of water in the distant past and it looks like you have some right now," said Campbell.
"Our thing is a piece of the puzzle. It fits into an overall picture."
