• With this “minimoon”, there are now three objects with lunar material identified as part of the Arjuna asteroid belt that follow orbits similar to those of the Earth-Moon system around the Sun.
• The finding made at the Complutense University of Madrid and the Astrophysical Institute of the Canary Islands opens the doors to commercial applications in the field of space mining

UCC-UCM, February 6, 2025. – The material from the surface of the asteroid 2024 PT_5,  which goes around the Sun in an orbit that resembles that of the Earth-Moon system and accompanied Earth for two months in 2024, has a lunar origin, a research led by the Complutense University of Madrid (UCM) and the Astrophysical Institute of the Canary Islands (IAC) has found.

The “minimoon”  2024 PT₅  was discovered in August 2024. In September, it was “trapped” by Earth’s gravity and remained under its influence until November. Its optical spectrum is very similar to those of lunar materials collected from the surface of the Moon by the missions Luna and Apollo.

“The orbital dynamics, very similar to that of the Earth-Moon system, and this surface composition support the conclusion that 2024 PT₅  may have its origin in the impact of an asteroid against the Moon”, explains Raul de la Fuente Marcos, researcher from the group AEGORA (Space Astronomy & Data Mining).

Another piece of evidence that makes researchers think that this object formed after that impact is its rotation, which lasts less than 60 minutes, although they do not rule out that 2024 PT₅  is in chaotic rotation and an average value cannot be computed. “This fact is characteristic of objects produced as a result of violent processes such as impacts”, argues De la Fuente Marcos.

The results of this research, published in Astronomy & Astrophysics Letters confirm those obtained independently by two studies carried out in the US, one led by Lowell Observatory and the Jet Propulsion Laboratory and a second one led by the Institute for Astronomy of the University of Hawai'i, also recently published. All three, carried out using different telescopes, confirm this lunar origin.

Three Arjunas with lunar origin

In order to obtain these results, the Spanish researchers carried out a photometric study from August 2024 until January 2025 using telescopes (TTT and TST) installed at the Teide Observatory on the island of Tenerife; the visible spectra were obtained in September using the Optical System for Imaging and Low Resolution Integrated Spectroscopy (OSIRIS) camera at the 10.4 m Gran Telescopio Canarias (GTC), located at the El Roque de Los Muchachos Observatory on the island of La Palma, Canary Islands. The computer calculations required to study and understand the dynamics of 2024 PT₅ were carried out at the UCM

In addition to this result of the lunar origin of 2024 PT₅, the Spanish researchers also argue that 2022 NX₁ has physical properties consistent with those of  2024 PT₅ and 469219 Kamo`oalewa, a quasi-satellite of our planet. These three asteroids are part of a structure known as the Arjuna asteroid belt that is made of near-Earth objects moving in heliocentric orbits.

“We do not have information of the composition of most Arjunas but the fact that three of them have surfaces with properties compatible with those of lunar materials suggests that asteroid impacts on the Moon help populating the Arjuna asteroid belt. This is an important but unexpected result”, emphasizes De la Fuente Marcos.

Applications in space mining

In recent years, the interest in promoting the commercial use of space has generated initiatives focused on carrying out economic activities on small bodies of the Solar System (asteroids and comets). One of these activities is space mining to find and extract mineral resources that are scarce on our planet.

“Although objects like 2024 PT₅ are relatively unimportant within the context of Earth’s Planetary Defense due to the fact that their impact probabilities are either zero or very small, they are however very attractive within the context of testing new technologies aimed at making the commercial use of the outer space and its resources easier”, points out the UCM researcher. Being closer and smaller, they can be used to mature the technologies that will facilitate a more extensive future use of the outer space that until recently was restricted to scientific research only.

“Discovering increasingly accessible objects and studying them spectroscopically to have a rough idea of ​​what minerals can be found in them facilitates the development of space missions with commercial applications”, concludes De la Fuente Marcos.

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.

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