How Is the Moon Changing?

Somewhat like a grape gradually shrinking to become a raisin, the Earth’s moon has been changing over the past several hundred million years. Scientists point to what they call “thrust faults” -- low ridges that resemble stair-step cliffs -- on the moon’s surface as evidence that the orb is shrinking as its interior cools. These fault-like ridges typically extend for a few miles, and their formations create “moonquakes,” with tremors that can be moderately strong, estimated to be “around five on the Richter scale,” says Thomas Watters, a senior scientist at the Smithsonian’s National Air and Space Museum in Washington.

To the moon, and beyond:

• Scientists analyzed data from a series of seismometers placed on the moon by various Apollo astronauts, beginning with the Apollo 11 crew in 1969. Four seismometers are still recording shallow moonquakes.
• In research published in a 2019 issue of Nature Geoscience, new analysis shows that a majority of quakes occur when the moon is at or near its apogee -- the farthest point from Earth in its orbit.
• NASA is planning to send a crew that will include a female astronaut to the moon by 2024. They are hoping to land on the lunar South Pole in the first of a series of lunar expeditions that may ultimately lead to a mission to Mars.