New features have been spotted on the surface of Mars by NASA's Mars Global Surveyor spacecraft.
The orbiter has taken periodic photographs of the planet's surface since it began its mission in 1997. Snaps of the same sand dune in 2002 and 2005 clearly show new features have emerged. The gullies in the later photograph are thought to have been caused by boulders tumbling down the slope.
The orbiter was designed to carry out observations for one Martian year (nearly two Earth years), but it has lasted much longer than its designers anticipated. Its mission was extended in 2001, and scientists have been able to use it to track seasonal changes on the red planet, as well as to pick up changes like the appearance of new boulder tracks.
The surveyor has also picked up new impact craters formed since the 1970s, which may mean age-estimating models need to be revisited. In addition, scientists have watched carbon dioxide deposits at Mars' south pole shrink for three consecutive Martian summers. They suggest there may be a climate change in progress.
"Our prime mission ended in early 2001, but many of the most important findings have come since then, and even bigger ones might lie ahead," said Tom Thorpe, project manager for Mars Global Surveyor.
NASA scientists say that the discoveries prove Mars is a more active and dynamic planet than was suspected. ®