We might think of the moon as a cold, dead chunk of rock, and it mostly is. However, a new analysis from Brown University claims there’s evidence of recent tectonic activity on the moon’s surface. The team didn’t need to launch a new lunar probe or land seismic sensors on the moon — NASA has already done that. Instead, researchers analyzed images from the Lunar Reconnaissance Orbiter (LRO) with an eye toward the prevalence of exposed bedrock.
Most of the surface is covered in lunar regolith, and scientists believe this material builds up quickly (on a geological scale). The LRO’s Diviner instrument measures the surface temperature across the moon, which can determine the surface composition — regolith tends to be colder than areas of exposed bedrock. They found more than 500 patches of exposed bedrock on narrow ridges, most of which were on the edges of lunar maria. Those are the large dark patches of the moon’s surface, and they don’t appear connected to volcanic activity in the moon’s early eons.
In the past, scientists have seen exposed bedrock on the moon as evidence of ancient lava flows. Indeed, NASA’s GRAIL mission in 2014 identified cracks in the moon’s crust where magma once flowed to the surface. Mapping out the exposed bedrock locations, the team found they lined up with the GRAIL cracks. Study co-author Peter Schultz says the correlation is nearly perfect, which suggests there’s some recent geological activity on the moon. The study calls this an Active Nearside Tectonic System, or ANTS.
The warmer spots (upper left) indicate regions with exposed bedrock.
The moon was most likely formed from material blasted off the primordial Earth by a massive impact. Lacking in mass, the moon cooled quickly and never developed the tectonic features seen on Earth. However, our local natural satellite has seen its fair share of impacts as well. The study speculates that the ANTS began billions of years ago following a large impact on the moon’s surface. The energy from that impact may still be driving small changes in the crust, pushing up portions of the bedrock faster than they can be covered with regolith.
These changes are minor, but they stand out on a planetoid with no other naturally occurring surface movement. We might not even notice the effect of long-ago impacts on an object like Earth.
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