A 33-foot-long object discovered orbiting Earth last year may have local origins, according to astronomers who believe the small asteroid may have come from a surprising place: the surface of the Moon.
First spotted last August using the University of Hawai’i’s ATLAS telescope in South Africa, researchers have now traced the asteroid’s origins to a large impact that likely occurred on the Moon long ago. Investigations into the unusual discovery, designated asteroid 2024 PT5, could provide new insights into the Moon’s geological history.
New studies of 2024 PT5’s unusual characteristics have led scientists to believe the object was likely associated with material that broke free from the lunar surface. This offers new potential avenues for understanding lunar asteroid science.
An Odd Asteroid Orbiting Earth
“We had a general idea that this asteroid may have come from the Moon, but the smoking gun was when we found out that it was rich in silicate minerals — not the kind that are seen on asteroids but those that have been found in lunar rock samples,” said Teddy Kareta, who lead the research into the peculiar asteroid.
An astronomer at Lowell Observatory in Arizona, Kareta’s research focuses on how modern properties of some of the smallest bodies in our Solar System can relate to their likely formation conditions. Such objects include comets, centaurs (objects orbiting the Sun between Jupiter and Neptune that cross the orbits of at least one of the giant planets), and asteroids like 2024 PT5.
Kareta’s past work, which included his dissertation, dealt with how these objects and changing, whether that involves them having recently begun, suddenly changed, or altogether stopped their cometary activity. As far as 2024 PT5, its lack of space weathering points to the fact that it has been in space for only a few thousand years.
Since initial observations of the unusual asteroid were made, subsequent observations by the Lowell Discovery Telescope and NASA’s Infrared Telescope Facility at Mauna Kea, Hawai’i, confirmed that sunlight being reflected off the space object’s surface was most similar to how light reflects off of lunar rock.
However, the object’s similarity to lunar rocks did not mean that other possibilities were not considered, including the chance that 2024 PT5 was no space rock at all; could it have been some sort of manufactured object?
Artificial Origins?
Another possibility included whether 2024 PT5 might have been human-made space debris from one of the many missions operating in orbit throughout the decades.
To determine whether this scenario might explain the object’s unique appearance, scientists at NASA’s Center for Near Earth Object Studies (CNEOS) conducted a careful analysis of its motion. This allowed them to calculate the effects of solar radiation pressure—that is, the force exerted by sunlight on objects drifting in space—revealing that they were too small to account for an artificial object.
“Human-made debris is usually relatively light and gets pushed around by the pressure of sunlight,” said Oscar Fuentes-Muñoz, a NASA postdoctoral fellow at JPL. “That 2024 PT5 doesn’t move this way indicates it is much denser than space debris.”
Clues to the Moon’s Hidden History
With the verification of 2024 PT5’s identity as an asteroid, the discovery officially doubles the small number of known asteroids that astronomers believe to have originated from the lunar surface. Presently, the only other asteroid confirmed to have come from the Moon is asteroid 469219 Kamo’oalewa, discovered in 2016.
However, as telescopes continue to improve, astronomers are confident that additional discoveries will be made that point to the lunar origins of near-Earth objects, which may offer additional opportunities to study the Moon and processes occurring on its surface, such as how craters form, as well as the nature of its subsurface material and changes it undergoes over long periods.
A key objective for astronomers like Kareta is to link a lunar asteroid with a specific impact crater in the future. This would help provide very detailed insights into how lunar craters are formed and how lunar material from deep below the surface can be ejected and eventually make its way to Earth thanks to asteroids like 2024 PT5.
As scientists like Kareta continue their work, ongoing discoveries involving the dynamics behind lunar phenomena will not only help to deepen our understanding of the Moon and its dynamic history, but will also lend themselves to the advancement of asteroid science.
“This is a story about the Moon as told by asteroid scientists,” Kareta recently said.
“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.”
The team’s findings were published in Astrophysical Journal Letters on January 14.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.