What "moonquakes" say about our shrinking Moon

The Moon is cooling, shrinking and stretching, causing “moonquakes” that shake the lunar surface, according to a new study in the journal Nature Geoscience.

The big picture: The research paints a picture of the Moon as a dynamic object, not the dead rock we’ve imagined it to be in the past. The findings could also have implications for our understanding of how other relatively small, rocky bodies in the solar system evolve over time.

What they found: By comparing images taken during the Apollo era with more modern ones of the lunar surface, scientists were able to determine specific ways that the Moon is actually cracking and wrinkling.

• Astronauts from the Apollo 11, 12, 14, 15 and 16 missions placed seismometers on the surface of the Moon. The Apollo 11 instrument failed after just a few weeks, but the other four recorded 28 shallow moonquakes from 1969 to 1977.
• Those shallow quakes have been a mystery until now.
• Scientists used an algorithm to locate their epicenters, then matched eight of those quakes to young faults on the lunar surface and found the Moon is tectonically active today.
• The study also shows that six of those eight quakes occurred when the Moon was near its farthest point from Earth. The researchers think that at that point in its orbit, the Moon is being stretched and warped, making the quakes more likely.

Buzz: “It’s one thing to be able to look at it in just one place, but to be able to observe features all over the Moon … is kind of cool,” Lunar Reconnaissance Orbiter scientist Noah Petro, who wasn’t involved in the study, told Axios.

Go deeper: The science case for returning to the Moon