As solar radiation breaks up water molecules in that atmosphere, light hydrogen would more readily fly off into space than would the heavier deuterium. Scientists thought Mars would have had to lose 90 percent of the water in its upper crust and atmosphere to produce a deuterium concentration five times higher than is found on Earth. However, that estimate depends on the further assumption that Mars started out with water similar to Earth's primeval supply. Dr. Leshin now says that probably isn't so. She analyzed water in crystals in a meteorite found in Antarctica in 1994.
Scientists believe the meteorite came from Mars.
She says the meteorite crystals indicate Mars's primitive water had nearly twice the deuterium as primitive water on Earth. Her research, published in the July 15 issue of Geophysical Research Letters, says Mars should have retained up to three times more water in its crust than expected. This conclusion enhances hopes for finding accessible liquid water on Mars - hopes already raised by the newly discovered gullies. But its main implication is to spur further research. Leshin warns that, suggestive as her work is, it does not show exactly how much water Mars actually has retained.