Scientists say the moon is slowly shrinking

Sunday, August 22, 2010

The moon, as seen in 2006
Image: Luc Viatour.

New research identifies cracks over the moon's crust that may have been created by the cooling and shrinking of it over the past billion or so years.

Scientists have discovered landforms littered across the moon's surface called lobate scarps that have apparently resulted from the moon's shrinking very slowly. These scarps were found all over the moon and appear to be minimally weathered, indicating that the geologic events that created them were fairly recent. This theory contradicts the claim that the moon is completely devoid of geologic activity.

Over the past billion years, about a quarter of the moon's 4.5 billion-year lifespan, it has shrunk about 200 meters (700 feet) in diameter. The scarps that are thought to have resulted from the contraction scenario were first identified near the lunar equator by cameras aboard the Apollo moon missions of the early 1970's.

NASA's Lunar Reconnaissance Orbiter recently photographed similar landforms in other locations on the moon, further supporting the theory that Earth's closest neighbor in space may in fact be shrinking.

The concept, however, is not a recent one. Scientists know that the moon's core was once very hot, causing it to expand. As the core cools, the moon naturally begins to contract.