From horseshoe to quasi-satellite and back again: the curious dynamics of Earth co-orbital asteroid 2015 SO2

摘要

Earth co-orbitals of the horseshoe type are interesting objects to study forpractical reasons. They are relatively easy to access from our planet and thatmakes them attractive targets for sample return missions. Here, we show thatnear-Earth asteroid (NEA) 2015 SO2 is a transient co-orbital to the Earth thatexperiences a rather peculiar orbital evolution characterised by recurrent,alternating horseshoe and quasi-satellite episodes. It is currently following ahorseshoe trajectory, the ninth asteroid known to do so. Besides moving insidethe 1:1 mean motion resonance with the Earth, it is subjected to a Kozairesonance with the value of the argument of perihelion librating around 270degrees. Contrary to other NEAs, asteroid 2015 SO2 may have remained in thevicinity of Earth's co-orbital region for a few hundreds of thousands of years.