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Brand new craters and gullies on Mars

The Mars Global Surveyor spacecraft has been orbiting Mars for the last nine years, and its camera has been snapping photos of the Red Planet's surface all the while.

By comparing images taken seven years apart, researchers have discovered new craters and gullies that have formed in the last seven years. Without these kinds of "before and after" pictures, it's difficult to tell how old craters and other surface features are, but the scientists can be sure that the craters and gullies that appear in the "after" photos are just babies.

Michael Malin of Malin Space Science Systems and his colleagues describe their findings in a study in the 8 December issue of the journal Science.

Although our solar system's planets are no longer pummeled by incoming objects the way they were in the past, small rocks still fall onto them today. Based on the information from the last seven years, Dr. Malin's team has concluded that the cratering rate on Mars is roughly the same as that of the Moon.

In the images that the scientists studied, the craters have shown up as dark spots, probably produced by dust kicked up during the impacts. The team also spotted recent changes in the walls of two craters that may have been caused by the recent flow of water.