# Planetary Chaos and the (In)stability of Hungaria Asteroids

## TL;DR

This study investigates the chaotic dynamics affecting the stability of Hungaria asteroids, revealing that planetary chaos, especially Mars's eccentricity, makes long-term predictions of their stability uncertain.

## Contribution

It demonstrates that the chaotic evolution of Mars's eccentricity critically influences Hungaria asteroid stability, challenging previous assumptions of their long-term stability.

## Key findings

- Hungaria stability depends on Mars's eccentricity evolution.
- Chaotic Mars eccentricity affects asteroid close approaches.
- Long-term stability predictions are unreliable due to planetary chaos.

## Abstract

The Hungaria asteroid group is located interior to the main asteroid belt, with semimajor axes between 1.8 and 2 AU, low eccentricities and inclinations of 16-35 degrees. Recently, it has been proposed that Hungaria asteroids are a secularly declining population that may be related to the Late Heavy Bombardment (LHB) impactors (\'Cuk et al. 2012, Bottke et al. 2012). While \'Cuk et al. (2012) and Bottke et al. (2012) have reproduced a Hungaria-like population that declined exponentially, the real Hungarias were never confirmed to be unstable to the same degree. Here we find that the stability of Hungarias is strongly dependent on the evolution of the eccentricity of Mars, which is chaotic and unpredictable on Gyr timescales. We find that the high Martian eccentricity chiefly affects Hungarias through close approaches with Mars, rather than planetary secular modes. However, current minimum perihelia of Hungarias (over Myr timescales) are not diagnostic of their long-term stability due to a number of secular and mean motion resonances affecting the Hungaria region (Milani et al. 2010). We conclude that planetary chaos makes it impossible to determine the effective lifetimes of observed Hungarias. Furthermore, long-term changes of Martian eccentricity could lead to variable Hungaria loss over time. We speculate that some of the most stable Hungarias may have been placed in their present orbit when the eccentricity of Mars was significantly higher than today.