Binary Asteroid Encounters with Terrestrial Planets: Timescales and Effects

TL;DR

This study investigates how close encounters with terrestrial planets affect binary asteroids' orbits, revealing that such encounters are frequent and can significantly alter their orbital parameters within million-year timescales.

Contribution

It combines analytical and numerical methods to quantify encounter timescales and orbital modifications for a wide range of binary asteroid configurations.

Findings

Close approaches (<10 Earth radii) occur within 1-10 million years for most binaries.

Encounters within 30 Earth radii happen on sub-million year timescales and impact wider binaries.

Planetary encounters can alter or halt processes like tidal and radiative evolution in near-Earth binaries.

Abstract

Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semi-major axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.