Ultra Low Velocity Ejecta Generated by Slow Impacts on Rubble Pile Asteroids

TL;DR

This study investigates ultra low velocity impacts on rubble pile asteroids, revealing how gravity-dependent minimal velocities influence ejecta speeds and extending understanding of impact processes at very low energies.

Contribution

It provides new experimental data and simulations on ejecta velocities from slow impacts under asteroid-like conditions, highlighting the role of gravity in ejecta dynamics.

Findings

Ejecta velocities decrease with impact energy at low velocities.

Gravity significantly affects the minimum observable ejecta velocities.

Results extend existing trends to lower impact energies.

Abstract

We examine ejecta generated by ultra low velocity impacts under asteroid conditions. In an environment of precisely controlled milligravity and under vacuum, impacts with velocities in the range of centimeters/second are performed with irregularly shaped impactors onto granular beds. The resulting ejecta velocities are compared to existing literature values and extend the observed systematic trends towards lower impact energies, broadening the parameter range. Simulations are performed to reason the systematics and the absence thereof for measurements performed at earth gravity. We find, that the cutoff induced by gravity dependent minimal observable velocities plays a crucial role in the values obtained for mean ejecta velocities.