Posted: Tue, Feb 21, 2012, 7:02 AM ET (1202 GMT)
Scientists analyzing images from a NASA spacecraft have identified features that formed relatively recently in the Moon's history. In a paper appearing in the March issue of Nature Geosciences, scientists describe the discovery of linear valleys, or graben, in the highlands on the far side of the Moon. Scientists identified the features in high-resolution images from NASA's Lunar Reconnaissance Orbiter. The graben, estimated to be no more than 50 million years old, occur where forces pull apart the lunar crust. That force overcame the gradual contraction of the lunar crust as its interior cools. That suggests to scientists that this contraction is weaker than previously thought, perhaps because it did not completely melt when it first formed.