Fresh Gullies, Rock Tracks Sighted on Mars’ Surface

The Martian surface has changed in the last few years, with new gullies and boulder tracks now visible, according to images released this week.

The photos, taken by the Mars Global Surveyor orbiter, suggest the Red Planet is more active than previously thought.

The spacecraft, which entered orbit eight years ago, captured images of two gullies on a sand dune that were not present in 2002. Scientists think the gullies might have formed when frozen carbon dioxide trapped by windblown sand vaporized, releasing gas that allowed the sand to flow freely.

Elsewhere, the craft photographed boulder tracks that did not exist two years ago. The tracks were probably left by dozens of boulders sent rolling down a slope by strong winds or an earthquake, scientists said.

Researchers also said that impact craters forming since the 1970s suggest that crater formation is a slow process, occurring at one-fifth the pace previously thought. The pace is important because it is used to estimate the age of Martian surfaces, said Michael Malin, principal investigator with the spacecraft camera program.

Images that show carbon dioxide deposits shrinking for the last three Martian summers near the South Pole suggest the planet may be undergoing a climate change.

The Mars Global Surveyor was launched in late 1996 and entered orbit 10 months later. The project is managed by NASA’s Jet Propulsion Laboratory in La Canada Flintridge.