Earth's mini-moon was the moon all along
Asteroid 2024 PT5 is a piece of the Earth's satellite after all


Asteroid 2024 PT5, which almost became a temporary mini-moon to Earth, was recently found to be a broken-off part of the moon itself. This discovery has led scientists to believe there are many more lunar-sourced space rocks waiting to be discovered. Studying these could provide new insight into the moon and its composition.
A moon of Earth's own
While 2024 PT5 never officially joined Earth's orbit, the almost-moon still became a topic of interest and is now understood to very likely be a piece of the actual moon, according to a study published in The Astrophysical Journal Letters. The rock was probably "flung into space by an impact on the lunar surface that occurred sometime within the past tens of thousand years," said The New York Times. "This is a story about the moon as told by asteroid scientists," said Teddy Kareta, a postdoctoral associate at Lowell Observatory in Arizona and the lead author of the study, in a NASA news release. "It's a rare situation where we've gone out to study an asteroid but then strayed into new territory in terms of the questions we can ask of 2024 PT5."
Researchers deduced the object's true nature by observing its movement through space, ruling out that it was human-made space debris. Then they "studied how the sunlight reflected off the small rock" and found it "didn't match that of any known asteroid type" — instead, the "reflected light more closely matched rocks from the moon," said USA Today. While this is convincing evidence that 2024 PT5 was once a piece of the moon, "unless you go and bring a sample back, you cannot tell for sure," said Vishnu Reddy, a professor of planetary science at the University of Arizona, to the Times.
Subscribe to The Week
Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

Sign up for The Week's Free Newsletters
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.
Rock the world
Past lunar missions "have provided precious samples for laboratory study, but space rocks chipped off the moon could add another dimension to our understanding," said Earth.com. Locating moon-sourced asteroids may allow researchers to study samples from deeper in the moon, which would otherwise be difficult to extract. Also, "if a lunar asteroid can be directly linked to a specific impact crater on the moon, studying it could lend insights into cratering processes on the pockmarked lunar surface," said the NASA release.
"Mini-moon" is a misnomer for 2024 PT5 because it approached the Earth from the inside, had its "orbit slightly altered by a very close approach with the Earth-moon system" and then receded "away from us on the 'outside' in an overall horseshoe trajectory," Kareta said to CNN. Thus it never truly became a second moon to the Earth. The asteroid is only the second one ever discovered to have lunar origins; scientists predict there may be many more. "As telescopes become more sensitive to smaller asteroids, more potential moon boulders will be discovered, creating an exciting opportunity not only for scientists studying a rare population of asteroids, but also for scientists studying the moon," said the NASA release.
Sign up for Today's Best Articles in your inbox
A free daily email with the biggest news stories of the day – and the best features from TheWeek.com
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.
-
Novel 'bone collector' caterpillar wears its prey
Speed Read Hawaiian scientists discover a carnivorous caterpillar that decorates its shell with the body parts of dead insects
By Peter Weber, The Week US
-
Judge blocks key part of Trump's elections overhaul
Speed Read Colleen Kollar-Kotelly's decision temporarily bars federal officials from requiring Americans to prove they are citizens to register to vote
By Rafi Schwartz, The Week US
-
Why is Crimea a sticking point between Russia and Ukraine?
Today's Big Question Questions over control of the Black Sea peninsula are stymying the peace process
By Joel Mathis, The Week US
-
How to see the Lyrid meteor shower
The explainer A nice time to look to the skies
By Devika Rao, The Week US
-
Full moon calendar: dates and times for every full moon this year
In depth When to see the lunar phenomenon every month
By Devika Rao, The Week US
-
Katy Perry, Gayle King visit space on Bezos rocket
Speed Read Six well-known women went into lower orbit for 11 minutes
By Peter Weber, The Week US
-
North America is 'dripping' into Earth's mantle
Under the radar Things are rocky below the surface
By Devika Rao, The Week US
-
Space ads could be coming to a sky near you
Under the radar Making space for commercial profits
By Devika Rao, The Week US
-
Scientists want to fight malaria by poisoning mosquitoes with human blood
Under the radar Drugging the bugs
By Devika Rao, The Week US
-
We could be living in a black hole
Under the radar And our universe may not be the only one
By Devika Rao, The Week US
-
Quantum leap: scientists skeptical of Microsoft's invention of a new state of matter
Under the Radar The tech company might become the proverbial 'boy who cried wolf' in quantum computing if the claims are disproven
By Theara Coleman, The Week US