New research shows the moon might be older than we thought

The moon appears to be roughly 40 million years older than previously thought, new research shows. (This story first aired on All Things Considered on October 27, 2023.)

SCOTT SIMON, HOST:

In December 1972, astronauts on the Apollo 17 mission went rock hunting on the moon.

(SOUNDBITE OF ARCHIVED RECORDING)

EUGENE CERNAN: Before we cover them up, let’s get them. I got to get a sample of that mother rock.

SIMON: They brought about 250 pounds of moon rock back to Earth. Those samples are still being studied today. NPR’s Regina Barber reports that scientists have now determined the moon is about 40 million years older than previously thought.

REGINA BARBER, BYLINE: The moon is roughly 4.5 billion years old. So what does an extra 40 million years mean on this time scale? Jenniker Greer is the lead author of the study, published in Geochemical Perspective Letters. Here’s how she sees it.

JENNIKER GREER: That 40 million years is significant when you look at the very dynamic early history of these two objects. A lot of stuff happened in the early solar system very quickly.

BARBER: In the early days of our solar system, an object the size of Mars smashed directly into a forming Earth.

GREER: And then they smushed together, and material sort of peeled off to form the moon.

BARBER: A hot moon that had a magma ocean. These Apollo 17 rock samples are crystals from that cooled ocean. To figure out how old these crystals are, scientists used radiometric dating. Because uranium decays into a specific kind of lead over time, scientists can use it to work backwards and get an age. The problem is, if some of that lead is lost over time or clumps together, it can throw off the age estimate. But new technology can help. For example, Greer was able to look at the sample on the atomic level to see if the lead was undisturbed.

GREER: The type of measurements that we do in this work would not have been possible 50 years ago. They wouldn’t have…