The long search for water on Mars— which could greatly boost the prospects of finding life or fossils there— is suddenly looking more promising. Recent images from the Mars Global Surveyor hint that water may still flow from underground reservoirs. And now two studies of meteorites sitting here on Earth offer a peek into the Martian past, when the planet's surface may have been covered with extensive, salty seas.
Carleton Moore, a chemist at Arizona State University, and his colleagues bored into the 1.2-billion-year-old Nakhla meteorite, a fragment of Mars that slammed into Egypt in 1911. Inside, they found water-soluble salts, including sodium chloride and calcium. "The simplest explanation is that they came from seawater that seeped into cracks in the rock and then evaporated," says Moore. The salts closely resemble those in Earth's oceans, he reports, but with a twist: "The water in the Martian meteorite has more calcium. We think that's because the calcium in our seas is removed by organisms to make shells."
In a complementary study, cosmochemist Laurie Leshin, also of ASU, examined another, 300-million-year-old Mars meteorite. Leshin measured the concentrations of deuterium, a heavy version of hydrogen, in the rock's crystals. As water from Mars escapes into space, deuterium is more likely than ordinary hydrogen to get left behind. According to Leshin's analysis, Mars started out with much more deuterium than previously thought. As a result, she thinks scientists need to double or triple their estimates of the amount of water still lurking in the planet's crust. All they need now is a working NASA spacecraft to look for that water firsthandÑsomething that will happen around 2003, if all goes well.
Photo by NASA/JPL/Malin Space Sciene Center
