• Asteroid 2023 FW14 was studied for the first time last year by researchers from the UCM and the IAC, it precedes the red planet in its orbit by 60 degrees
• Although the orbital evolution of the 16 previously known trojans is long-term stable, the one of the new trojan is not, giving rise to two theories about its origin

UCC-UCM, March 21, 2024. The ``Universidad Complutense de Madrid" (UCM), together with the ``Instituto de Astrofísica de Canarias" (IAC) observe and describe for the first time the object 2023 FW14, a trojan asteroid that shares Mars' orbit.

The trojan asteroids are minor bodies that share the orbit of a planet. Mars hosts the second-largest trojan group with 17 known objects. Only Jupiter hosts a larger trojan population.

A planet can host two sets of trojans, one precedes the planet 60 degrees in its orbit (circling the Lagrange point L4) and the other follows 60 degrees behind the planet (at the Lagrange point L5). The object 2023 FW14, observed with the ``Gran Telescopio Canarias" (GTC) and published in the international peer review journal Astronomy & Astrophysics belongs to the first group, the one preceding Mars in its orbit; only one (1999 UJ7) of the 16 previously known trojans is part of this group.

Although most known Mars trojans may have remained as such since they were formed, 2023 FW14 reached its current trojan orbit about one million years ago and it may leave it in about ten million years, according to results from the numerical calculations presented.

"Although the orbital evolution of the 16 previously known trojans is long-term stable, that of the new one is not. There are two possibilities regarding its origin: It could be a fragment of the trojan 1999 UJ7 or perhaps it was captured from the near-Earth asteroid population that crosses Mars' orbit," explains Raúl de la Fuente Marcos, a researcher at the ``Departamento de Física de la Tierra y Astrofísica" of the UCM.

In addition, most of the previously known Mars trojans have similar spectra and, therefore, surface chemical composition. The spectrum of 2023 FW14 obtained with GTC is different, but similar to that of the other L4 trojan, 1999 UJ7.

Numerical simulations carried out using computers at the UCM during 2023 and 2024 confirmed that the observed object was an L4 Mars trojan, only the second known.

"The spectrum obtained with GTC on April 18, 2023, from the ``Observatorio del Roque de los Muchachos" in the island of La Palma, let us place this object within the context of the known Mars trojans. The observation window was very short, just a couple of weeks. The coordination of orbital analyses and observations required quick thinking, a bit of good luck, and skill", points out de la Fuente Marcos regarding the research performed.

Adding new objects to the list of Mars trojans will lead to a deeper understanding of these objects, the trojans, which were originally discovered with pen-and-paper calculations. "The study of real trojans as opposed to those predicted mathematically gives us the ability to evaluate how reliable our theoretical models are", de la Fuente Marcos concludes.

Bibliographic reference: R. de la Fuente Marcos, J. de Leon, C. de la Fuente Marcos, M.R. Alarcon, J. Licandro, M. Serra-Ricart, S. Geier, A. Cabrera-Lavers. “Dynamics of 2023 FW14, the second L4 Mars trojan, and a physical characterization using the 10.4 m Gran Telescopio Canarias”. A&A, 683, L14, 21 March 2024. DOI: 10.1051/0004-6361/202449688 (https://doi.org/10.1051/0004-6361/202449688).

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