Lurking just beneath the surface of Mars is enough water to cover the entire planet ankle-deep, says Los Alamos National Laboratory scientist Bill Feldman. Feldman on Saturday released the first global map of hydrogen distribution identified by instruments aboard NASA’s Mars Odyssey spacecraft and offered initial minimum estimates of the total amount of water stored near the Martian surface. His presentation came at the annual meeting of the American Association for the Advancement of Science in Denver. For nearly a year, Los Alamos’ neutron spectrometer has been carefully mapping the hydrogen content of the planet’s surface by measuring changes in neutrons given off by soil, an indicator of hydrogen likely in the form of water-ice, within about 35 degrees latitude of the north and south poles. “It’s becoming increasingly clear that Mars has enough water to support future human exploration,” Feldman said. “In fact, there’s enough to cover the entire planet to a depth of at least five inches, and we’ve only analyzed the top few feet of soil.”

The observation of small gullies on Mars was one of the more unexpected discoveries of the Mars Observer Camera (MOC) aboard the Mars Global Surveyor spacecraft. The characteristics of these gullies suggested that they were formed by flowing water and soil and rocks transported by these flows. They appeared to be surprisingly young, as if they had formed in the last few million years or even more recently. This was a major surprise because the presence of liquid water seemed impossible on Mars in such a recent past. In their initial analysis, the MGS Camera investigators Mike Mallin and Ken Edgett proposed a scenario involving ground water seepage from a sub-surface liquid water reservoir located a few hundred meters or less below the surface. The existence of such an aquifer would have had major consequences for the future of Mars exploration and the possibility of life. However, the process capable of maintaining such a shallow aquifer at temperatures above the freezing point of water remained unclear. Analysing the MGS Camera data archive, we were able to find example of gullies originating from the top of isolated peaks and from dune crests. In these cases, the involvement of a subsurface aquifer was unlikely.

Soon after Mars was formed, it was bombarded by numerous large meteorites and asteroids. Scientists have discovered an unexpectedly large grouping of impact basins buried under Mars’ northern plains that resulted from this pounding. They used Mars Orbiter Laser Altimeter (MOLA) topographic data to find them, because they can