The moon’s cratered face was previously thought to be 4.42 billion years old, or about 10 million years old. But now crystal samples taken by the rock satellite half a century ago suggest that the moon is about 40 million years older than we knew.
The moon was formed over 4 billion years ago when a body about the size of Mars collided with the ancient Earth. The material created by the collision clumped together and became the moon shapes aspects of life on Earth from the tides to the rhythms of animal behavior.
The zircon crystals were collected as part of the Apollo 17 mission in 1972 and were recently dated by researchers to determine when the moon formed. Since the crystals couldn’t have formed when the moon’s surface melted – they would have melted and the evidence of their existence would have been erased – the team knows they must come from the time when the moon cooled into the stoic gray ball, who he is today.
Previous research had suspected that the moon was a few tens of millions of years older than its previously known age, but the new team’s research found published today in Geochemical Perspectives Letters, confirmed the older timeline.
“It is amazing to have evidence that the rock you are holding is the oldest part of the moon we have found so far. It’s an anchor point for so many questions about Earth,” Jennika Greer, a geophysicist at the Field Museum in Chicago and lead author of the study, said at a museum release. “If you know how old something is, you can better understand what happened to it in its history.”
Using atom probe tomography, the researchers examined how lead atoms were distributed in the zircon crystals obtained. Similar to other ancient dating methodsresearchers used the radioactive decay rates of atoms to reverse the clock and understand when they were new – that is, when the magma ocean that was the moon cooled and formed our satellite.
“In an hourglass, sand flows from one glass bulb to another, with the passage of time indicated by the accumulation of sand in the bottom bulb,” said Philipp Heck, a planetary scientist at the Field Museum and the University of Chicago, in a statement. “Radiometric dating works similarly, counting the number of parent atoms and the number of daughter atoms they have been converted into. The timing can then be calculated since the transformation rate is known.”
The team found that the zircon crystals are at least 4.46 billion years old, 40 years older than previous estimates. It may be a blink of an eye in cosmic time, but a helpful fine-tuning of the Moon’s timeline.
We will almost certainly learn more about how the moon formed Crewed Artemis missions. NASA aims to send humans to the moon and establish a permanent presence there sometime after 2025.
More: Apollo astronauts may have brought back a piece of ancient Earth from the moon