Monday, October 12, 2009
NASA found 99% pure water ice on Mars
NASA’s Mars Reconnaissance Orbiter (MRO) has revealed sub-surface water ice that may be 99 percent pure, halfway between the North Pole and the equator on the Red Planet.“We knew there was ice below the surface at high latitudes of Mars, but we find that it extends far closer to the equator than you would think, based on Mars’ climate today,” said Shane Byrne of the University of Arizona, a member of the High Resolution Imaging Science Experiment, or HiRISE, which runs the high-resolution camera on NASA’s Mars Reconnaissance Orbiter.“The other surprising discovery is that ice exposed at the bottom of these meteorite impact craters is so pure,” Byrne said.“The thinking before was that ice accumulates below the surface between soil grains, so there would be a 50-50 mix of dirt and ice. We were able to figure out, given how long it took that ice to fade from view, that the mixture is about one percent dirt and 99 percent ice,” he added.Scientists used several instruments on the Mars Reconnaissance Orbiter, or MRO, in quick succession in detecting and confirming highly pure, bright ice exposed in new craters, ranging from 1.5 feet to 8 feet deep, at five different Martian sites.In August 2008, the orbiter’s Context camera team examined their images for any dark spots or other changes that weren’t visible in earlier images of the same area. Meteorites usually leave dark marks when they crash into dust-covered Mars terrain.The HiRISE team, which bases its operations at the UA Lunar and Planetary Laboratory, followed up in September 2008 by taking high-resolution images of the dark spots.“We saw something very unusual when we followed up on the first of these impact craters, and that was this bright blue material poking up from the bottom of the crater. It looked a lot like water ice. And sure enough, when we started monitoring this material, it faded away like you’d expect water ice to fade, because water ice is unstable on Mars’ surface and turns directly into water vapour in the atmosphere,” Byrne said.A few days later that September, the orbiter’s “CRISM” team used their Compact Reconnaissance Imaging Spectrometer for Mars and got the spectral signature of water ice exposed in one of the impact craters, further clinching the discovery.How far water ice extends toward the equator depends largely on how much water has been available in the Martian atmosphere in the recent past.“The ice is a relic of a more humid climate not very long ago, perhaps just several thousand years ago,” Byrne said.