Forming Massive Terrestrial Satellites through Binary-Exchange Capture

TL;DR

This study explores the potential for terrestrial planets to capture massive satellites through binary-exchange collisions, demonstrating that Earth-sized planets could acquire moons of significant mass and maintain stable, circular orbits over long timescales.

Contribution

It introduces a novel mechanism for satellite formation around terrestrial planets via binary-exchange capture, supported by simulations and tidal evolution analysis.

Findings

Massive satellites (0.01 - 0.1 Earth masses) can be captured by terrestrial planets.

Captured satellites can achieve long-term orbital stability and circularization.

The process is plausible for Earth-like planets at 1 AU in the Solar System.

Abstract

The number of planetary satellites around solid objects in the inner Solar System is small either because they are difficult or unlikely to form, or that they do not survive for astronomical timescales. Here we conduct a pilot study on the possibility of satellite capture from the process of collision-less binary-exchange and show that massive satellites in the range 0.01 - 0.1 Earth masses can be captured by earth-sized terrestrial planets in a way already demonstrated for larger planets both in the Solar System and possibly beyond. In this process, one of the binary objects is ejected, leaving the other object as a satellite in orbit around the planet. We specifically consider satellite capture by an earth in an assortment of hypothetical encounters with large terrestrial binaries at 1 AU around the Sun. In addition, we examine the tidal evolution of captured objects and show that orbit circularization and long-term stability are possible for cases resembling the Earth-Moon system.