Using Mars co-orbitals to estimate the importance of rotation-induced YORP break-up events in Earth co-orbital space

Abstract

Both Earth and Mars host populations of co-orbital minor bodies. A large number of present-day Mars co-orbitals is probably associated with the fission of the parent body of Mars Trojan 5261 Eureka (1990 MB) during a rotation-induced Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) break-up event. Here, we use the statistical distributions of the Tisserand parameter and the relative mean longitude of Mars co-orbitals with eccentricity below 0.2 to estimate the importance of rotation-induced YORP break-up events in Martian co-orbital space. Machine-learning techniques (k-means++ and agglomerative hierarchical clustering algorithms) are applied to assess our findings. Our statistical analysis identified three new Mars Trojans: 2009 SE, 2018 EC4, and 2018 FC4. Two of them, 2018 EC4 and 2018 FC4, are probably linked to Eureka but we argue that 2009 SE may have been captured, so it is not related to Eureka. We also suggest that 2020 VT1, a recent discovery, is a transient Martian co-orbital of the horseshoe type. When applied to Earth co-orbital candidates with eccentricity below 0.2, our approach led us to identify some clustering, perhaps linked to fission events. The cluster with most members could be associated with Earth quasi-satellite 469219 Kamo‘oalewa (2016 HO3) that is a fast rotator. Our statistical analysis identified two new Earth co-orbitals: 2020 PN1, which follows a horseshoe path, and 2020 PP1, a quasi-satellite that is dynamically similar to Kamo‘oalewa. For both Mars and Earth co-orbitals, we found pairs of objects whose values of the Tisserand parameter differ by very small amounts, perhaps hinting at recent disruption events. Clustering algorithms and numerical simulations both suggest that 2020 KZ2 and Kamo‘oalewa could be related.

Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa

“…A third possibility is that Kamoʻoalewa originates in the Earth-Moon system, perhaps as impact ejecta from the lunar surface 45 or as a fragment of a parent NEO's tidal or rotational break up during a close encounter with Earth-Moon 46 . Three NEOs, 2020 PN 1 , 2020 PP1, and 2020 KZ2, have been identified as having orbital parameters cluster near Kamoʻoalewa's closely enough that they may be break-up companions 47 . The reflectance spectrum of Kamoʻoalewa (as reported in the present work) lends support to the lunar ejecta hypothesis.…”

Orbital pathways for a Lunar-Ejecta Origin of the Near-Earth Asteroid Kamo`oalewa

“…It has been suggested by [5] that three small NEAs -2020 PN1, 2020 PP1, and 2020 KZ2 -may have the same provenance as Kamo'oalewa due to their close orbital clustering and the similarities they exhibit in their orbital evolutions on timescales of a few thousand years. We have not investigated the orbital dynamics of these individual objects, but their resemblance to Kamo'oalewa's orbital elements implies that our results for Kamo'oalewa could also be applicable to these objects' origin.…”

“…Unlike the long-term stable population of Trojan asteroids co-orbiting with Jupiter, most near-Earth asteroids (NEAs) have chaotic orbits with dynamical lifetimes much shorter than the age of the Solar System [3], and asteroids stably co-orbiting with the Earth on such timescales are uncommon. An assessment of Earth's co-orbital companions shows a total population of only twenty-one objects, with two Trojan-type, six in the QS state, and thirteen undergoing HS motion; all of these objects are in their co-orbital states only temporarily, typically on less than decadal timescales [4,5]. The recently discovered quasisatellite of the Earth, (469219) Kamo'oalewa, is exceptional among the Earth's co-orbitals due to the longer-term persistence of its HS-QS transitions [6][7][8][9].…”