David Susko and his colleagues at Louisiana State University analyzed geochemical and surface morphology data from Elysium using instruments on board NASA's Mars Odyssey Orbiter (2001) and Mars Reconnaissance Orbiter (2006). Through crater counting, they found differences in age between the northwest and the southeast regions of Elysium—about 850 million years of difference. They also found that the younger southeast regions are geochemically different from the older regions, and that these differences related to igneous processes, not secondary processes like the interaction of water or ice with the surface of Elysium in the past.