OCEANS on Mars would have been acidic, a new analysis of the planet鈥檚 chemistry suggests. This could explain why scientists have failed to clinch the case for Martian oceans, despite NASA鈥檚 rovers finding evidence of water on the planet.
On Earth, oceans absorb carbon dioxide from the atmosphere and deposit it as carbonate rock. Scientists have looked for, but failed to find, similar deposits on Mars. Now Alberto Fairen from the Autonomous University of Madrid (UAM) in Spain and colleagues have shown why Martian oceans would not have formed carbonates.
Earlier this year, NASA鈥檚 rover Opportunity found iron-rich minerals and sulphate salts at its landing site, Meridiani Planum. The researchers worked out that oceans contaminated with such compounds would interact with an early Martian atmosphere rich in carbon dioxide and become acidic, preventing carbonates from forming (Nature, vol 431, p 423).
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But other experts are not convinced that the problem has been solved. Joshua Bandfield of Arizona State University in Tempe, who has studied the distribution of carbonates on Mars, warns that the geology of Meridiani Planum might not be representative of the rest of Mars.
