Images taken by NASA’s Lunar Reconnaissance Orbiter (LRO) show there are relatively recently formed cliffs in the lunar crust indicating the moon shrank in the recent past and may still be doing so. The space agency introduced the images and discussed the discovery publicly on Thursday.
The cliffs, called lobate scarps, formed less than a billion years ago, quite possibly about a hundred million years ago, which is young in terms of the moon, according to NASA. Based on their size, NASA believes that the distance between the moon’s center and its surface shrank by about 300 feet.
The scarps themselves are relatively small, with the largest being only about 300 feet high and extending for about several miles across small craters, according to NASA.
It’s the craters that have clued the agency in to their young age. Small craters on the moon’s surface don’t last long because it is constantly being hit with meteors that would destroy them on impact, the agency said.
Further, the scarps look relatively undegraded, also pointing to their young age, NASA said. The age of the scarps means that the moon could have been cooling and shrinking very recently.
The new images aren’t the first time NASA has identified lobate scarps on the moon, but they do confirm that previous ones spotted are not isolated to one area of the moon but are in fact a global phenomenon, the agency said.
NASA’s Apollo missions first identified scarps but, since those missions only photographed 20 percent of the lunar surface near the equator, scientists were unsure if the cliffs were merely the result of local activity in the area. The new scarp discovery however -- showing a number of scarps at higher latitudes -- indicates they exist across the moon, according to NASA.
NASA aims to use the LRO’s Narrow Angle Cameras to build a global map of the moon to identify additional scarps. Further research on them will try to determine if the Earth’s gravitational pull and tides are having any effect on them.
NASA said the discovery of the scarps helps them better understand global processes on the moon. Further, by tracking geologic features like the scarps, scientists can better understand not just the history of the moon, but the entire solar system.
NASA's Exploration Systems Mission Directorate – which includes researchers from both NASA and academia -- funded the research that led to the scarps’ discovery. Scientists from Arizona State University, Cornell University, Brown University and Johns Hopkins University were a part of the research team.