Report: Mars crust holds two times or more water than thought

June 29, 2000
Web posted at: 11:26 a.m. EDT (1526 GMT)

By Richard Stenger
CNN.com Writer

(CNN) -- Mars could hold two to three times more water under its surface than previously estimated, according to a new study.

The conclusion is based on a comparison between the amount of deuterium, a heavier form of hydrogen, in the martian atmosphere and the amount found in a martian meteorite.

The report, to be published in the July 15 issue of Geophysical Research Letters, comes on the heels of a NASA announcement that the surface of Mars shows signs of recent liquid water activity.

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Deuterium combines with oxygen to make so-called heavy water, which is chemically the same as regular water, except that deuterium atoms replace hydrogen atoms.

In the martian atmosphere, water vapor has a ratio of deuterium to hydrogen five times greater than that of water on Earth.

This difference has been attributed to the escape of hydrogen from the martian atmosphere over time. Hydrogen is lighter than deuterium and escapes more easily, which would explain the much higher level of deuterium in the atmosphere of Mars, according to the report.

Postulating that Mars and Earth had the same ratio of the two gases billions of years ago, scientists have calculated that the red planet has lost 90 percent of the water in its atmosphere and crust.

Found in 1994 in Antarctica, this 12-g Mars meteorite holds clues about the red planet's wet past.

Yet Arizona State University geochemist Laurie A. Leshin came to another conclusion after studying water crystals in a Mars meteorite, found in the Antarctic in 1994.

She determined that Mars had a deuterium-to-hydrogen ratio nearly twice that of Earth before atmospheric escape could have taken place.

Since martian water originally contained higher deuterium levels than previously thought, Mars should have lost two or three times less water than scientists have estimated before, according to Leshin.

That water should still exist today within the crust of the red planet, she said.

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Geophysical Research Letters
Dr. Laurie Leshin Homepage
Arizona State University

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