A Green Valley for Phoenix

The Phoenix Mars Mission, a collaborative mission between Arizona State University and NASA, is the first of the Mars Scout class landers. It is specially designed to dig under the Martian surface to discover the composition of the hydrogen rich compound that gamma ray imaging showed to be just under the surface at the poles. Everyone is hoping the ice is going to be made up of water, but that's what Phoenix is all about. The first landing site that had been chosen has been shown to be covered in lander-sized boulders, and is now an unsatisfactorily risky landing site. The next most promising site, nick-named the Green Valley, is a very shallow valley near the north pole. The article deals with how they used the images from both the Mars Reconnaissance Orbiter and the Mars Global Surveyor to determine the risks involved in the previously selected landing site, and how they're using the data still coming in about the other possible sites to figure out the best place to land.