  We present an analysis of lifetimes and resonances of Earth Trojan Asteroids
(ETAs) in the MEGASIM data set (Yeager & Golovich 2022). Trojan asteroids
co-orbit the Sun with a planet but remain bound to the Lagrange points, L4
(60{\deg} leading the planet) or L5 (60{\deg} trailing). In the circular
three-body approximation, the stability of a Trojan asteroid depends on the
ratio of the host planet mass and the central mass. For the inner planets, the
range of stability becomes increasingly small, so perturbations from the
planets have made primordial Trojans rare. To date there have been just two
ETAs (2010 TK7 and 2020 XL5), several Mars Trojans, and a Venus Trojan
discovered. The estimated lifetimes of the known inner system Trojans are less
than a million years, suggesting they are interlopers rather than members of a
stable and long-lasting population. With the largest ETA n-body simulation to
date, we are able to track their survival across a wide initialized parameter
space. We find the remaining fraction of ETAs over time is well fit with a
stretched exponential function that when extrapolated beyond our simulation run
time predicts zero ETAs by 2.33 Gyr. We also show correlations between ETA
ejections and the periods of the Milankovitch cycles. Though Earth's orbital
dynamics dominate the instabilities of ETAs, we provide evidence that ETA
ejections are linked to resonances found in the variation of the orbital
elements of many, if not all of the planets.
