The moon's real age

The moon may have joined Earth's orbit sooner than experts thought

(Image credit: Stefano Guidi / Getty Images)

Our planet's trusty satellite has been around longer than we previously thought. Scientists analyzed lunar crystals brought back by Apollo 17 astronauts in 1972, and determined the moon was actually 4.46 billion years old, 40 million years older than previously believed, per a new study published in the journal Geochemical Perspective Letters. “It moves the goal post,” Jennika Greer, who worked on the study, told The Washington Post. “It pushes back the minimum age of the moon formation.”

Researchers studied minerals in lunar dust called zircons, which are “cosmic timepieces that started ticking once that magma ocean cooled and solidified,” per the Post. The zircon pieces analyzed in the study are the oldest to date. However, many were skeptical that the age was accurate, given that these crystals were older than any other samples. “It’s been controversial for the last 50 years, since the 1970s when the astronauts brought back the samples from the moon,” Bidong Zhang, who led the study, told the outlet. “Apollo rocks were very consistent at 4.3 billion years old. That’s why people are like: ‘Why would this age be different?’"

Scientists have long believed that the moon came to be after a Mars-sized object crashed into the Earth resulting in a large fragment breaking off and becoming the moon. The debate was when this occurred. "Our atom probe analysis concluded the study and leaves no doubt about the 4.46-billion-year age of the zircon," Phillipp Heck, senior author of the study, told Newsweek. "I was very happy to see that with our new study the old age of the zircon crystals could be nailed down without a doubt.”

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Devika Rao has worked as a staff writer at The Week since 2022, covering science, the environment, climate and business. She previously worked as a policy associate for a nonprofit organization advocating for environmental action from a business perspective.