Can the Moon be a source of Earth’s co-orbitals?

Earth’s co-orbitals are asteroids in mean motion resonance with the Earth. They are of interest because of their dynamics that is typically stable and because they represent low Δv targets for asteroid mining companies. Recently, spectroscopic analysis of the co-orbital asteroid Kamo‘oalewa, and of two objects temporarily captured by the Earth, have indicated the possibility of a lunar origin for these bodies. Several subsequent studies addressed this possibility by means of numerical integration, especially for the case of Kamo‘oalewa, and attempted to identify the crater that could have launched it.

Here we compute the steady-state number of Earth’s co-orbitals deriving from lunar ejecta by computing their frequency and lifetime by means of long-term numerical simulations (about 50 My), paying attention to their co-orbital regime (quasi-satellite, horseshoe, tadpole or compound) and orbital eccentricity and inclination. The number and size are estimated by employing scaling laws that characterize the impact processes. In parallel, we compute the population of Earth’s co-orbital that the Main Belt can yield using NEOMOD3 [2]. Both outcomes are compared with the known population obtained from JPL Horizons [3].

The results show that the co-orbitals that the Moon can provide have a lower average eccentricity and inclination than those that the Main Belt can provide. Moreover, the existing population can be explained by the NEOMOD3 model. With NEOMOD3 the co-orbitals’ provenance is mainly from the inner Main Belt and we find that about half of them are in the tadpole regime while only 2 Earth Trojans are officially recognized, likely due to observational bias. The tadpole population in our results are eccentric and inclined, and we identify 3 additional objects as Trojans, namely, 2005 UH6, 2005 QQ87 and 2024 JR16.

Finally, the main source of uncertainty is given by impact process’ laws and thus we suggest that a systematic spectroscopic and dynamical characterization of Earth’s co-orbital can help reduce the uncertainty on those scaling laws.

The work that we will present is based on [1].

References

[1] Alessi, E.M., Jedicke, R., 2026. The steady-state population of Earth’s co-orbitals of lunar provenance. Icarus 455, 117109.

[2] Nesvorný, D., Vokrouhlický, D., Shelly, F., Deienno, R., Bottke, W.F., Fuls, C., Jedicke, R., Naidu, S., Chesley, S.R., Chodas, P.W., Farnocchia, D., Delbo, M., 2024. NEOMOD 3: The debiased size distribution of Near Earth Objects. Icarus 417, 116110.

[3] https://ssd.jpl.nasa.gov/horizons/