Basaltic quasi-mini-moon: Characterizing 2024 PT5 with the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope⋆

Abstract

Context. Small bodies in Earth-like orbits, the Arjunas, are good targets for scientific exploration, and space mining or in situ resource utilization (ISRU) trials as they enable low-cost missions. The subset of these objects that experience recurrent temporarily captured flyby or orbiter episodes are among the best ranked in terms of accessibility. Only a handful of objects are known to have engaged in such a dynamical behavior. Finding and characterizing more of them may help to expand scientific and commercial research activities in space over the next few decades. Asteroid 2024 PT_{5 is a recent finding that shows dynamical traits in common with this group.Aims. Here we investigate the orbital context of 2024 PT5 and its spectral and rotational properties.Method. We studied the short-term orbital evolution of 2024 PT5 using direct N-body simulations. We identified its spectral class from the visible reflectance spectrum and used photometric observations to derive its rotational properties. Observational data were obtained with the OSIRIS camera spectrograph at the 10.4 m Gran Telescopio Canarias and the Two-meter Twin Telescope.Results. Asteroid 2024 PT5 experiences recurrent co-orbital engagements and episodes in which it has negative geocentric orbital energy while inside a geocentric distance under three Hill radii, which we call quasi-mini-moon events. Its visible spectrum is consistent with that of lunar-like silicates. Photometric data suggest a rotation period ≲1 h.Conclusions. The discovery of 2024 PT5 confirms that events resembling temporary captures are relatively frequent and involve objects larger than a few meters, suitable as accessible targets for scientific research activities and demonstrating ISRU technologies.}