- This is the third “mini-Moon” with lunar-like material identified as part of the Arjuna asteroid belt, where objects follow similar orbits around the Sun to that of the Earth-Moon system.
IAC, February 6, 2025. – Near-Earth asteroid 2024 PT5 orbits around the Sun following a trajectory very similar to that of the Earth-Moon system, and during two months of 2024, it accompained our Earth on its journey. This asteroid has material on its surface that was originated in the Moon, as it has been proved by a research led by the Insituto de Astrofísica de Canarias (IAC) and the Universidad Complutense de Madrid (UCM), in Spain.
This “mini-Moon” was discovered in August 2024. In September it “got trapped” by the Earth’s gravity and stayed under its influence until November. Its optical spectrum is very similar to that exhibited by lunar material collected by the Luna and Apollo missions. “Studying the composition of these objects is fundamental to fully understand their origin and their evolution through millions of years”, says Julia de León, responsible of the Solar System group at the IAC.
“Its orbital dynamics, very similar to that of the Earth-Moon system, and its composition, supports the conclusion that 2024 PT5 could have its origin on an asteroidal impact on the Moon”, explains Raúl de la Fuente Marcos, researcher of the Space Astronomy and Data Mining group at the UCM.
Another finding that supports the hypothesis that this object originated after the impact of an asteroid on the Moon is its spin rotational period, which is lower than 60 minutes, although chaotic rotation is not totally discarded and so, it is not possible to assign it an avarage value. “This behaviour is characterisitc of objects generated after violet events, like impacts”, referes de la Fuente Marcos.
This research work, published in Astronomy & Astrophysics Letters aligns with the results of another two US independent investigations, recently published, one led by the Lowell Observatory and the Jet Propulsion Laboratory, and the other by the Astronomical Institute of the University of Hawai. All three research works, done using different telescope facilities, get to the same conclusion, confirming the lunar origin of 2024 PT5.
Three Arjunas with lunar origin.
In order to analyse the surface of 2024 PT5, the Spanish team carried out an astrometric follow-up – image acquisition- from September 2024 to January 2025, using the TTT1 and TTT2 telescopes (Two-meter Twin Telescopes), and the TST (Transient Survey Telescope), managed by Light Bridges in collaboration with the IAC at the Teide Observatory. In addition, both optical spectra and photometry -light curve- with the 10.4m Gran Telescopio CANARIAS (GTC), located at the El Roque de Los Muchachos Observatory, were obtained in September 2024. The computations associated with the dynamical study of this object were done at the UCM.
Additionally, Spanish researchers also conclude that asteroid 2022 NX1 has physical properties similar to those of 2024 PT5 and 469219 Kamo’oalewa, an Earth’s quasi-satellite. The three objects are part of a structure called the Arjuna asteroid belt, composed of asteroids near the Earth that orbit the Sun.
“We do not have compositional information about the majority of the Arjunas, but the fact that three of these objects have surfaces properties compatible with lunar material suggests that asteroidal impact on the Moon are contributing to the population of the Arjuna belt. This is an unexpected and important result”, remark both de la Fuente Marcos and de León.
Bibliographic reference: “Basaltic quasi-mini-moon: Characterizing 2024 PT5 with the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope” A&A, 694, L5 (2025). DOI: 10.1051/0004-6361/202452713
