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	Mars Hides Much More Water, Study Suggests By Andrew Bridges Pasadena Bureau Chief posted: 07:00 am ET 28 June 2000

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New research claims the crust of Mars may harbor up to three times more water than previously thought, providing the latest blow to the tarnished notion that the planet today is a dry, lifeless place.

The study suggests that Mars may have lost far less water to space over time than scientists have believed. That leaves the tantalizing possibility the planet still holds sizable reservoirs of water that future space missions could tap in the search for life.

These Martian gullies appear to have been carved by water. A new study points toward higher estimates for the amount of water on the Red Planet.

The paper describing the work, by Arizona State University geochemist Laurie Leshin, comes on the tail of a report last week that vast stores of liquid water may lie just below the surface of Mars.

Leshins work compared the amount of deuterium, a heavy form of hydrogen, found in water in the Martian atmosphere, to that in a meteorite blasted from the planets surface 3 million years ago and discovered in Antarctica in 1994.

Leshin found that ancient water-bearing crystals in the meteorite QUE 94201 were richer in deuterium than expected and thus similar to the water in the planets present-day atmosphere. The unexpected similarity in deuterium ratios suggests the planet has held on to two to three times as much water as previously estimated.

Martian meteorite QUE 94201 was found in Antarctica in 1994.

"They are more similar than we thought they were, although they are still different," said Leshin, an assistant professor at the Arizona States Tempe campus. "Its the size of the difference between the two thats less than previously thought." Leshins report will be published in the July 15 issue of the journal Geophysical Research Letters.

Many scientists have assumed that water on Mars and Earth began with comparable deuterium-to-hydrogen ratios. With the passage of time, however, the Red Planets atmosphere lost much of its comparatively lighter hydrogen, leaving behind the heavier deuterium, boosting in the process its overall proportion.

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Today, the water in the atmosphere of Mars has a deuterium-to-hydrogen ratio 5.2 times that on Earth. To reach that level, scientists have suggested Mars lost as much as 90 percent of the water in its upper crust and atmosphere.

But Leshin found in analyzing minute amounts of ancient water in the 0.42-ounce (12-gram) meteorite that its deuterium-to-hydrogen level was not equal to but actually double the ratio found in terrestrial water.

Leshins finding implies that once Mars began to lose hydrogen to space, it did so from a reservoir that was already twice as rich in deuterium as water found on Earth.

"You lose some of it, but you dont have to lose as much to get to where the atmosphere is today," said John Jones, a planetary scientist at NASAs Johnson Space Center.

David Paige, a University of California, Los Angeles planetary scientist, called the concept a reasonable one.

"This is only thing I have seen that has the potential of tracing back and giving us a snapshot of what those conditions were," said Paige.

Deuterium's origin

How Mars started off with deuterium-rich water is a far trickier question.

Leshin suggests that early in Mars history it lost significant amounts of hydrogen to enhanced extreme ultraviolet radiation from the then-young sun. Alternatively, she said, comets could have pummeled the planet in large number to re-supply it with water that already had elevated deuterium levels.

Nor does the new work answer the most pressing question of just how much water Mars has today.

"Its an incredibly evolving field right now," said Bruce Jakosky, a professor of geology at the University of Colorado. "There isnt a single good estimate."

Scientists also caution that even tripling the estimate of how much water Mars might have does not necessarily mean the planet is swimming in the stuff.

"The real story is that, hey, youve still lost as much as 70 to 90 percent of the water," Jones, of NASA, said. "That could be big news to someone who wants to go to Mars and drill a well."