Mars is a more dramatically changing place than scientists had ever imagined. Thanks to its long lifetime, the Mars Global Surveyor has spotted a gully coming down the side of a sand dune that didn't exist just three years ago. The gully could have formed when frozen carbon dioxide was suddenly warmed up enough that it evaporated, releasing gas that flowed downhill like a liquid. Mars Global Surveyor is still very healthy, and could be making observations 5-10 years from now.