Water on Mars: Look just below the surface

Ingenious detective work by University of Guelph researchers has uncovered the strongest evidence yet of large reservoirs of water today at the Martian surface.


The water isn't a liquid, but is chemically bound up in a white layer of mineral salts located only a penny's thickness below the planet's characteristic red surface.

The iron and sulphur compound that makes up this white layer contains as much as 18 per cent water by weight, says Iain Campbell, a retired University of Guelph physics professor who led the research.

"Nobody has gone up there with a water sniffer. But this is the best evidence we have from the surface of Mars until someone does," Campbell said in an interview yesterday.

On Earth, water is often part of minerals that contain sulphates. Each molecule of the mineral gypsum, for instance, contains two molecules of water making it valuable in drywall.

Physics professor Ralf Gellert, a co-investigator on the Guelph research team, said the white mineral layer wasn't limited to a just a few spots in the Columbia Hills region where NASA's Spirit rover has been exploring. "It seems to be a very common thing in this area." he said.

The chemically trapped water is most likely what's left from surface water pools that evaporated, the researchers speculate.

Water that could be easily extracted at the Martian surface would overcome a key obstacle facing colonization of Earth's solar system neighbour. A $1.7 billion NASA Mars Science Laboratory scheduled to land on the planet in three years is equipped to confirm the present-day existence of water beyond any doubt.

Indirect indications water still exists on the red planet have come from orbiting satellites, which recorded high concentrations of hydrogen, the element that combines with oxygen to form H{-2}O, or water. Spirit and its rover twin, Opportunity, have also found erosion and other geological signs of the presence of water in the distant past.

The novel Guelph findings are based on both serendipity and scientific ingenuity.

The serendipity arose when one of Spirit's six wheels locked up. The balky wheel carves a deep track in the Martian soil, churning up a bright white underlying layer at four sites in the Columbia Hills.

This white material was checked with a sophisticated chemical analyzer on Spirit, called an alpha particle X-ray spectrometer, which Gellert helped design when at a research institute in Germany.

Roughly the size and shape of a soda can, the analyzer is manoeuvred on the rover's articulated arm to touch surface areas considered scientifically promising. It detects the unique X-ray signatures of many elements, but not of lighter elements such as hydrogen or oxygen.

The ingenuity entered when Guelph's Campbell, assisted by physics colleague Joanne O'Meara, devised a novel technique to extract information about these lighter elements from bits of the spectrometer's measurements scientists had been dismissing as interference.

"We made our calculations more and more rigorous and the water didn't go away," said Campbell.

The University of Guelph is the only place doing this sophisticated analysis. A research paper spelling out the results has been provisionally accepted for publication in a special issue of an American Geophysical Union journal.

An improved version of the X-ray spectrometer is being assembled in Brampton at MacDonald, Dettwiler and Associates Ltd. to fly on the Mars Science Laboratory in 2010.

Other key contributors to the Guelph results were students Mary Lee and Christiane Mallett. The work is financed by the Natural Science and Engineering Research Council, a federal funding agency.