Scientists Discover That Earth’s Tiny Asteroid Guest May Be a Fragment of the Moon

A near-Earth object was likely cast into space following an impact thousands of years ago. Its presence could provide fresh perspectives on asteroid and lunar science.

The minor near-Earth object 2024 PT5 drew global attention last year after it was detected by a telescope lingering in proximity to—but not orbiting—our planet for several months. The asteroid, measuring about 33 feet (10 meters) in width, doesn’t present a threat to Earth; however, its solar orbit is closely aligned with that of our planet, suggesting it may have originated nearby.

As described in a study published in the Astrophysical Journal Letters, researchers have gathered additional evidence supporting that 2024 PT5 is of local origin: It seems to consist of rock detached from the moon’s surface and expelled into space after a significant impact.

“We had a prevailing suspicion that this asteroid might have originated from the moon, but the definitive proof came when we discovered it was abundant in silicate minerals—not the types commonly found on asteroids but those identified in lunar rock samples,” stated Teddy Kareta, an astronomer at Lowell Observatory in Arizona, who spearheaded the research.

“It appears to have been in space for only a brief period, possibly just a few thousand years, as there is no noticeable space weathering that would have altered its spectrum towards red.”

Initially spotted on Aug. 7, 2024, by the Sutherland telescope in South Africa, which is part of the University of Hawai’i’s Asteroid Terrestrial-impact Last Alert System (ATLAS), Kareta’s team subsequently utilized data from the Lowell Discovery Telescope along with the NASA Infrared Telescope Facility (IRTF) at Mauna Kea Observatory in Hawai’i. This analysis revealed that the spectrum of sunlight reflected from the small object’s surface did not correspond with any known asteroid classification; rather, the reflected light closely resembled that of lunar rock.

Not Rocket Science (Old)

A second hint emerged from analyzing the object’s motion. In addition to asteroids, remnants from the Space Age, like old rockets from historic launches, are also present in Earth-like orbits.

The variance in their trajectories relates to how each type reacts to solar radiation pressure, which stems from the momentum of photons—quantum particles of light emitted by the sun—exerting a minuscule force upon impact with solid objects in space. Over time, this momentum exchange from numerous photons can slightly move an object, either accelerating or decelerating it. While a human-made item, like a hollow rocket booster, behaves like a lightweight tin can catching the breeze, a natural entity like an asteroid is significantly less influenced.

In order to eliminate the possibility of 2024 PT5 being space debris, scientists at NASA’s Center for Near Earth Object Studies (CNEOS), managed by the agency’s Jet Propulsion Laboratory in Southern California, scrutinized its motion. Their accurate calculations of the object’s movement under the influence of gravity eventually enabled them to seek out additional motion resulting from solar radiation pressure. In this particular case, the impacts were found to be negligible, reinforcing that 2024 PT5 is likely of natural origin.

“Space junk and space rocks behave slightly differently in the cosmos,” explained Oscar Fuentes-Muñoz, a co-author of the study and NASA postdoctoral fellow at JPL collaborating with the CNEOS team. “Artificial debris is generally lighter and can be easily impacted by sunlight pressure. The fact that 2024 PT5 does not behave in this manner suggests it is considerably denser than space debris.”

Asteroid Lunar Investigations

The identification of 2024 PT5 doubles the count of recognized asteroids believed to originate from the moon. Asteroid 469219 Kamo’oalewa was identified in 2016 with an orbit similar to that of Earth.

sun, suggesting that it could have also been expelled from the lunar terrain following a significant collision. As telescopes advance in sensitivity to minor asteroids, an increasing number of potential lunar boulders will be identified, presenting an exhilarating prospect not just for researchers examining a unique category of asteroids but also for those investigating the moon.

If a lunar asteroid can be definitively associated with a particular impact crater on the moon, analyzing it could provide valuable understanding into the cratering mechanisms on the scarred lunar surface. Furthermore, substances from deep within the lunar crust—in the shape of asteroids nearing Earth—might become available for future researchers to examine.

“This is a narrative about the moon as envisioned by asteroid researchers,” remarked Kareta. “It’s a distinctive circumstance where we’ve ventured out to examine an asteroid but then wandered into uncharted questions regarding 2024 PT5.”