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

TL;DR

This paper investigates the complex orbital dynamics of asteroid 2015 SO2, revealing its recurrent horseshoe and quasi-satellite episodes and its long-term stability near Earth's co-orbital region.

Contribution

It provides the first detailed analysis of asteroid 2015 SO2's peculiar, recurrent co-orbital behavior and its resonance interactions with Earth.

Findings

Asteroid 2015 SO2 exhibits recurrent horseshoe and quasi-satellite episodes.

It is currently in a horseshoe orbit, the ninth known to do so.

The asteroid may have remained near Earth's co-orbital region for hundreds of thousands of years.

Abstract

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