Astronomers have declared that the moon is shrinking after spotting wrinkles all over the lunar surface. The tell-tale contraction marks were discovered by U.S. scientists who examined thousands of photographs of the moon’s surface taken by a Nasa orbiter.
Some of the wrinkles are several miles long and rise tens of metres above the dusty terrain. Researchers believe they arise from the moon decreasing in size by around 200 metres across its diameter. The moon’s mean diameter is generally calculated to be 3,474 kms.
The prospect of a shrinking moon is not new to planetary experts. When the moon formed it had a hot core, much like that of the Earth, which caused it first to expand and then contract as it cooled down.
The latest findings suggest the moon could still be cooling, a process that causes the surface to compress and form the wrinkle-like features, known as lobate scarps.
A team led by Thomas Watters at the Smithsonian Institution in Washington DC studied high-resolution images of the moon taken over the past year by Nasa’s latest moon probe, the Lunar Reconnaissance Orbiter. The spacecraft cameras provide the most detailed images of the moon ever taken from orbit.
Fourteen lobate scarps were identified, at sites as far apart as the lunar equator and near the poles. The features are so pristine scientists think they could be no more than a billion years old.
“Not only could they be indicating recent contraction of the moon, they may be indicating that the moon is still contracting,” said Mr. Watters. “Until now, we really had no evidence of cooling and the contraction of the moon that would go along with it. This isn’t anything to worry about. The moon may be shrinking, but not by much. It’s not going anywhere.” Scientists believe the moon formed after a Mars-sized object slammed into the Earth and produced an enormous cloud of debris 4.5bn years ago. The debris coalesced into the fledgling moon and warmed up as particles were crushed together and some released radiation.
A shrinking moon overturns the view that our natural satellite is a cold lump of rock and suggests it might still have a warm core and be geologically active.
“There’s a general impression that the moon is geologically dead, that anything of significance that happened geologically up there happened billions of years ago. This population of young scarps indicates that really isn’t the case,” said Mr. Watters.
Similar markings were photographed on the moon during the Apollo missions. Scientists will now compare those pictures with the latest images to see if anything has changed in the past 40 years.
Over the next three to four years the Lunar Reconnaissance Orbiter will build a detailed map of the moon’s surface. “It will be very interesting to see the overall distribution of all lobate scarps and other telltale features, as more images of the lunar surface are returned,” said Peter Grindrod, a planetary geologist at University College London. “The extent and age of these features will help reveal whether there was a global period of contraction on the moon, and ultimately tell us more about how the moon formed and evolved.” Copyright: Guardian News & Media 2010
