Orbiter’s Long Life Helps Scientists Track Changes on Mars NASA

New gullies that did not exist in mid-2002 have appeared on a Martian sand dune. That’s just one of the surprising discoveries that have resulted from the extended life of NASA’s Mars Global Surveyor, which this month began its ninth year in orbit around Mars. Boulders tumbling down a Martian slope left tracks that weren’t there two years ago. New impact craters formed since the 1970s suggest changes to age-estimating models. And for three Mars summers in a row, deposits of frozen carbon dioxide near Mars’ south pole have shrunk from the previous year’s size, suggesting a climate change in progress.