WATER on Mars could be locked up in sponge-like salts, which might explain why water was found in the unlikeliest regions of the Red Planet last year.
In 2003, scientists reported that the Odyssey spacecraft had detected unusually high levels of hydrogen in the soil 鈥� a telltale sign of water 鈥� in some equatorial regions of Mars, where water ice would be unstable. This finding, coupled with the discovery of sulphates by the Mars Rover Opportunity at its landing site, prompted David Vaniman and his colleagues at the Los Alamos National Laboratory in New Mexico to simulate the Martian environment and study the water-retention capabilities of magnesium sulphate, which is widespread on Mars.
The team found that even under very dry Martian-like conditions the salts form a variety of hydrated crystals which can retain high amounts of water, enough to account for most of the hydrogen seen in some regions by Odyssey (Nature, vol 431, p 663). Studying these hydrates could also reveal how wet Mars has been in the past. But the hydrates are very sensitive to their environment, so any attempt to bring them back to Earth for analysis would be futile. Rather, they will have to be studied on Mars itself.
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