spacetoday.net: Moon is shrinking slightly

Posted: Fri, Aug 20, 2010, 6:56 AM ET (1056 GMT)
Lunar cliffs created by shrinkage (NASA)

Scientists announced Thursday they have found evidence that the Moon has shrunk by a small amount over the last billion years, evidence that it is not geologically dead. Images from NASA's Lunar Reconnaissance Orbiter have revealed cliffs called lobate scarps that formed within the last billion years. These cliffs, scientists conclude, are caused by the Moon's interior cooling and contracting. The amount of shrinkage is small, no more than 100 meters, but provides evidence that the Moon remains geologically active to at least a small degree to this day. That activity could explain some fraction of the moonquakes detected by lunar seismometers placed there during the Apollo program.