Transient Terrestrial Trojans: Comparative Short-term Dynamical Evolution of 2010 TK7 and 2020 XL5

Abstract

The Trojan asteroids of Mars and Jupiter are long-term stable, those of Earth are expected to be just transient companions. The first Trojan of our planet, 2010 TK7, was discovered in 2010 and its resonant state was found to be transient. Here, we provide a preliminary assessment of the current dynamical status and short-term orbital evolution of 2020 XL5, a recently discovered near-Earth asteroid that might be the second known representative of this elusive population. Our calculations show that the current orbit determination of 2010 TK7 is consistent with that of a robust, present-day, yet transient, L4 Earth Trojan. In sharp contrast, the current orbit determination of 2020 XL5 is still too uncertain and its orbital evolution too chaotic to confirm a current Trojan engagement with Earth, although the nominal orbit shows such a behavior. More observations are required to provide a conclusive answer.