Earth's fleeting companions, known as "mini-moons," continue to surprise astronomers with their origins. A recent discovery involving 2024 PT5, a bus-sized object, has raised intriguing questions about the nature of this near-Earth asteroid, as studies suggest it may be more than just space debris—it could very well be a fragment of the Moon.
Discovered on August 7, 2024, by the South Africa-based observatory of the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS), 2024 PT5 measures approximately 33 feet (10 meters) wide. Researchers have confirmed it safely passed Earth at about 1.1 million miles, and due to its distinct orbit, it is not at risk of colliding with our planet.
Astronomers led by Teddy Kareta, of Lowell Observatory, have analyzed the asteroid's surface using both the Lowell Discovery Telescope and NASA's Infrared Telescope Facility. The object reflects light almost identically to rocks brought back from the Moon during NASA’s Apollo 14 mission. Kareta remarked, "It looks like it hasn’t been in space for very long, maybe just a few thousand years or so." This led researchers to propose its origins might trace back to the Moon itself, likely ejected after intense impacts.
This isn't the first time the connection between near-Earth asteroids and our Moon has been suggested. 2024 PT5 becomes the second confirmed lunar fragment, following 469219 Kamo’oalewa, identified back in 2016. With at least 16 additional candidates already suggested for lunar origin, the research team is tantalized by the potential to discover more about these mini-moons and their origins.
According to the findings published on January 14, 2025, data shows the asteroid’s composition is rich in silicate minerals commonly found in lunar rocks but rare among typical asteroids. "The reflection characteristics point toward it originating from the Moon’s highlands after being knocked off during some massive impact," Kareta shared.
Despite earlier assumptions about the asteroid being capable of becoming a mini-moon—orbiting around Earth—it maintained what scientists call a "horseshoe orbit," bringing it close but never actually capturing it as temporary satellite. "It was never really in orbit, but the vocabulary here to describe what it did do ... hardly caters to fun nicknames," Kareta noted humorously.
Ruling out the possibility of 2024 PT5 being space debris, researchers determined the object had significant mass, inconsistent with human-made items like rocket boosters. Oscar Fuentes-Muñoz, who worked alongside Kareta, stated, "Human-made debris ... gets pushed around by the pressure of sunlight. That 2024 PT5 doesn’t move this way indicates it is much denser than space debris." This pivotal research adds substantial confidence to the assertion of its lunar origin.
The discovery of 2024 PT5 strengthens the hypothesis some near-Earth asteroids, particularly those sharing heliocentric orbits like Earth, may originate from lunar impacts. Robert Jedicke, expert at the University of Hawaii, stated, "The hypothesis ... could be chips off the moon is perfectly reasonable." He and others agree the work done by Kareta and his team is thorough and convincing.
Looking ahead, the research community is eager to study these lunar fragments. Areas of interest include linking lunar asteroids to specific craters on the Moon, which could reveal more about both the Moon's surface and its geological history. Kareta pointed out, "If there’s one of something, it’s easy to convince yourself it’s an outlier. If there are two, then there’s a whole population out there waiting to be recognized and studied."
With new telescopes like the Vera Rubin Observatory set to come online soon, there is optimistic anticipation for the identification of additional lunar asteroids. Kareta concluded, "We’re going to have to get savvier about how we can whittle down ... interestingly lunar-like orbits before we go out to the telescope. It’s like searching for needles in a haystack, except the needles don’t look too different from the hay until you get them up close."
Through this multifaceted investigation of Earth’s mini-moon, scientists not only deepen their knowledge of our celestial neighbors, but they also bolster planetary defense initiatives, thereby enhancing our ability to understand, anticipate, and potentially mitigate any future threats posed by asteroids approaching our planet.