Erosion and accretion by cratering impacts on rocky and icy bodies

TL;DR

This study models cratering impacts on icy bodies using simulations to derive scaling laws for erosion and accretion, revealing that impacts on terrestrial planets generally lead to net accretion, while those on moons cause net erosion.

Contribution

It introduces new scaling laws for erosion and accretion during impacts on icy bodies, expanding understanding beyond rocky bodies and aiding predictions in planetary formation.

Findings

Impacts on terrestrial planets tend to cause net accretion.

Impacts on moons like Rhea and Europa tend to cause net erosion.

Derived scaling laws are applicable to planetary formation scenarios.

Abstract

During planet formation, numerous small impacting bodies result in cratering impacts on large target bodies. A fraction of the target surface is eroded, while a fraction of the impactor material accretes onto the surface. These fractions depend upon the impact velocities, the impact angles, and the escape velocities of the target. This study uses smoothed particle hydrodynamics simulations to model cratering impacts onto a planar icy target for which gravity is the dominant force and material strength is neglected. By evaluating numerical results, scaling laws are derived for the escape mass of the target material and the accretion mass of the impactor material onto the target surface. Together with recently derived results for rocky bodies in a companion study, a conclusion is formulated that typical cratering impacts on terrestrial planets, except for those on Mercury, led to a net accretion, while those on the moons of giant planets, e.g., Rhea and Europa, led to a net erosion. Our newly derived scaling laws would be useful for predicting the erosion of the target body and the accretion of the impactor for a variety of cratering impacts that would occur on large rocky and icy planetary bodies during planet formation and collisional evolution from ancient times to today.