A recently published study in Nature Geosciences revealed that the moon is contracting, and it’s causing moonquakes.
Dr. Wayne Schlingman, director of the Arne Slettebak Planetarium at The Ohio State University, explained the reason for the gradually shrinking lunar landscape.
“The moon was hot when it was formed. Anything that was hot, when it cools down shrinks. If we take a balloon, fill it up at room temperature and stick it in the refrigerator, it’s going to be smaller,” Schlingman said.
A NASA research team reviewed information obtained from a network of seismometers that were installed on the surface of the moon beginning in 1969 during the Apollo moon-landings.
Fault scarps, or wrinkles in the lunar surface, were created by cooling and contraction of the moon’s interior, which caused cracks (thrust faults) to develop. The cliffs are stairs-shaped and extend for several miles, reaching tens of feet in height.
After analyzing thousands of images, evidence gathered by NASA’s Lunar Reconnaissance Orbiter in the past decade, a data re-analysis indicates that the moon is 164 feet smaller compared to the early 1970s.
Between 1969 and 1977, 28 moonquakes ranging in magnitude from 2.0 to 5.0 occurred, and eight happened within 20 miles of a thrust fault. Of those, 75 percent were recorded at apogee, when the moon and Earth were farthest apart, which is assocated with tidal stress from Earth’s gravitational pull.
Photographic evidence of landslides and displaced boulders strongly suggest that moonquakes are still happening.
Schlingman said that new rovers sent to space will provide more information in the coming decade about current seismic activity.
“When we send people there in five or 10 years, we’ll be able to lay out a seismic network that can last longer,” he said.
Schlingman said that by increasing our understanding of the properties of the moon, we will learn more about other planets.
Robotic evidence of a quake on Mars earlier this yearm and steep cliffs on Mercury about 1,000 feet tall, provide further evidence of these dynamic processes in our solar system.