A new investigation by NASA's Jet Propulsion Laboratory (JPL) suggests that the asteroid 2024 PT5, approximately 10 meters in diameter, may be a fragment of the Moon ejected after an impact thousands of years ago. The findings, published in the Astrophysical Journal Letters, provide evidence supporting this lunar origin, potentially enhancing our understanding of asteroids and lunar geology.
2024 PT5 was detected on August 7, 2024, by NASA's ATLAS telescope in South Africa. Although it has never orbited Earth, its solar orbit closely resembles that of our planet, indicating a nearby origin.
The research team, led by astronomer Teddy Kareta from Lowell Observatory, utilized advanced telescopes, including the Lowell Discovery Telescope and NASA's Infrared Telescope Facility (IRTF), to analyze the reflected light from the asteroid's surface. Their analysis revealed that the light spectrum does not match any known type of asteroid but is similar to lunar rock samples collected by previous space missions.
Kareta noted, "What really confirmed the lunar origin was the mineral-rich silicate composition, typical of the Moon's surface but rare in asteroids." Additionally, the lack of space weathering—typically causing celestial objects to appear redder over time—suggests that 2024 PT5 was ejected relatively recently, possibly just a few thousand years ago.
Crucial insights also emerged from analyzing 2024 PT5's movement. Researchers at the Center for Near Earth Object Studies (CNEOS) calculated how solar radiation pressure influences its trajectory. Unlike artificial objects, which are often lighter and more sensitive to solar pressure, calculations indicated that 2024 PT5 is too dense to be space debris, confirming its natural origin.
This discovery doubles the number of known asteroids with a likely lunar origin, adding to the previously identified 469219 Kamo'oalewa from 2016. As telescopes become more sensitive, the identification of additional lunar fragments is expected. These studies not only deepen our understanding of lunar impacts but may also reveal material from the Moon's deeper layers.
Kareta remarked that this research represents "a story about the Moon told by asteroid scientists," providing new perspectives on impact studies and lunar surface formation.