During the last manned mission to walk on the moon, Apollo 17 in 1972, American astronauts Harrison Schmitt and Eugene Cernan collected approximately 110.4 kilograms of rock and soil samples that were brought back to earth for further study.

Half a century later, crystals of the mineral zircon inside a fragment of igneous rock collected by Schmitt reveal clues that allow scientists to gain a deeper understanding of the moon’s formation and its precise age.

The moon is about 40 million years “older” than previously thought as it formed more than 4.46 billion years ago, within 110 million years of the birth of the solar system, scientists said Monday, based on the analyzes of the crystals.

The leading hypothesis for the formation of the Moon holds that during the chaotic early history of the Solar System, a Mars-sized object called Theia slammed into the primordial Earth. From there, magma, molten rock, was blasted into space, forming a debris disk that orbited Earth and merged with the moon. But the exact time of the formation of the moon is difficult to determine.

The mineral crystals were able to form after the magma cooled and solidified. The researchers used a method called atomic probe tomography to confirm the age of the zircon crystals, which formed after the giant impact.

“I like the fact that this study was done on a sample that was collected and brought to Earth 51 years ago. At the time, atom probe tomography had not yet been developed, and scientists would not have imagined the types of analyzes we do today,” said cosmochemist Philipp Heck, senior director of research at the Field Museum in Chicago, a professor at the University of Chicago and senior author of the study published in the journal Geochemical Perspectives Letters.

Interestingly, all the oldest minerals found on Earth, Mars and the Moon are zircon crystals. “Zircon, not diamond, lasts forever.” added UCLA planetary scientist and study co-author Bidong Zhang.

The rock containing the zircon was collected in the Taurus-Littrow Valley at the southeastern edge of the lunar Mare Serenitatis (Sea of ​​Serenity) and stored at NASA’s Johnson Space Center in Houston.

“Zircons are very hard and survive the breakdown of rocks during weathering,” Heck said.