Astronomers have identified a small near-Earth object (NEO), designated 2024 PT5, which appears to have originated from the Moon.
Discovered in August 2024, the object remained near Earth for several months, moving in an Earth-like orbit around the Sun.
Research published in The Astrophysical Journal Letters suggests that the asteroid may have been ejected from the lunar surface after a high-energy impact thousands of years ago.
Discovery and characteristics
2024 PT5 was first detected on August 7, 2024, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Sutherland, South Africa.
Follow-up observations by the Lowell Discovery Telescope and NASA’s Infrared Telescope Facility (IRTF) revealed its composition and trajectory details. Scientists determined that its reflectance spectrum closely matches lunar rock samples rather than known asteroid types.
Image credit: NASA/JPL-Caltech
The asteroid is estimated to measure 8 – 12 m (26 – 40 feet) in diameter and is rich in pyroxene, a mineral commonly found in lunar highland rocks.
Unlike most asteroids with similar spectral characteristics, which are typically olivine-rich, 2024 PT5’s composition aligns more closely with lunar material.
Observations further suggest a lack of space weathering, indicating that the object has been exposed to the space environment for only a few thousand years.
Natural or artificial origin?
Researchers examined the motion of 2024 PT5 under solar radiation pressure to confirm its natural origin. Artificial objects, such as defunct rocket stages, experience greater momentum from sunlight due to their lower density and hollow structure.
However, the motion of 2024 PT5 was consistent with that of a dense, natural object, ruling out the possibility of it being human-made debris.
Connections to the moon
This marks only the second time a near-Earth object has been linked to the Moon. The first, asteroid 469219 Kamo’oalewa, was identified in 2016 and shares a similar Earth-like orbit. Both objects are believed to have been ejected into space after impacts on the lunar surface.
Based on spectral data, researchers suggest that 2024 PT5 may originate from the Moon’s highlands.
The implications of this discovery are significant. Additional findings of similar objects could indicate a previously unrecognized population of lunar-origin NEOs, providing insights into the mechanics of lunar impacts, such as the depth, materials, and energy involved in ejection processes.
Challenges and future research
Tracking objects like 2024 PT5 is challenging. Its slow, close approach to Earth in 2024 enabled detailed study, but its trajectory is highly sensitive to gravitational interactions. Numerical models indicate that its orbit becomes unpredictable before 1937 and after 2084, complicating long-term predictions. Additional astrometric data could help refine these models.
The study showcases the importance of developing new observational techniques to identify and characterize small lunar-origin objects. Researchers state that combining visible and near-infrared spectral data is crucial for reliably distinguishing lunar materials from asteroidal ones.
Upcoming advancements in telescope technology, such as the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST), are expected to improve the detection of such objects.
Broader implications
A better understanding of lunar-derived NEOs could connect the fields of asteroid and lunar science. If associated with specific craters on the Moon, these objects could provide direct evidence of impact processes and possibly grant access to material from beneath the lunar surface. Such studies might also advance planetary defense strategies and assist in dating the Moon’s surface.
The discovery of 2024 PT5, with its potential lunar origin, adds a new dimension to the study of NEOs, providing researchers a unique opportunity to link asteroid science with the Moon’s history.
References:
1 Study Finds Earth’s Small Asteroid Visitor Likely Chunk of Moon Rock – NASA/JPL – January 22, 2025
2 On the Lunar Origin of Near-Earth Asteroid 2024 PT5 – Theodore Kareta, Oscar Fuentes-Muñoz, Nicholas Moskovitz, Davide Farnocchia, and Benjamin N. L. Sharkey – American Astronomical Society –
The Astrophysical Journal Letters, Volume 979, Number 1. – January 14, 2025 – DOI 10.3847/2041-8213/ad9ea8 – – OPEN ACCESS
3 Asteroid 2024 PT5 to become Earth’s temporary new mini-moon on September 29 – The Watchers – September 15, 2024