Pure water ice in the subsurface of Mars

Scientists are seeing sub-surface water ice that may be 99 percent pure halfway between the north pole and the equator on Mars, thanks to quick-turnaround observations from orbit of fresh meteorite impact craters on the 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." 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. More...