Can the Moon be the source for minimoons?

We examine the plausibility of a lunar origin of natural objects that have a negative total energy, that is, E_T<0, with respect to the geocenter while they have a geocentric distance r <3R_H, where R_H is the Earth's Hill radius, a population of objects that we will refer to as 'bound'.  They are a super-set of the informally-named population of 'minimoons' that make at least one orbit around Earth in a frame rotating with the Earth's orbit and have a geocentric distance r <R_H at some point while E_T<0.  Bound objects are also a dynamical subset of the population of Earth's co-orbital population, objects in a 1:1 mean motion resonance with the Earth or, less specifically, on Earth-like orbits.  Only two minimoons have been discovered to date, 2006 RH₁₂₀ and 2020 CD₃, while 2024 PT₅ and 2022 NX₁ meet our condition for 'bound'.  The likely source region of co-orbital objects is either the asteroid belt, the Moon (that is, lunar ejecta), or a combination of both.  Earlier works found that dynamical evolution of asteroids from the asteroid belt could explain the observed minimoon population, but visual reflectance spectra of 2020 CD₃, 2024 PT₅, and Earth's co-orbital Kamo'oalewa are more consistent with lunar basalts than any asteroid spectra, suggesting that the ejection and subsequent evolution of material from the Moon's surface contributes to the minimoon population and, more generally, Earth's co-orbital population. We report on our numerical calculations of the steady-state size-frequency distribution of the bound population given our current understanding of the lunar impact rate, the energy of the impactors, crater-scaling relations, and the relationship between the ejecta mass and speed [1].  We numerically integrate the trajectory of lunar ejecta and calculate the statistics of 'prompt' bounding that take place immediately after ejection, and 'delayed' bounding that occurs after the objects have spent time on heliocentric orbits.  A sub-set of the delayed bound population composes the minimoon population.  We find that lunar ejecta can account for the observed population of bound objects but uncertainties in the crater formation and lunar ejecta properties induce an uncertainty range on the predicted population spanning orders of magnitude.  If the bound objects can be distinguished as lunar or asteroidal in origin based on their spectra, it may be possible to constrain crater formation processes and the dynamical and physical evolution of objects from the asteroid belt into near-Earth space.

[1] Jedicke et al. 2025, Icarus  438, 116587