# An experimental study of low-velocity impacts into granular material in reduced gravity

## TL;DR

This study investigates low-velocity impacts into granular material under reduced gravity conditions, revealing how impact dynamics such as penetration depth and collision duration behave differently from terrestrial impacts, with implications for asteroid landing strategies.

## Contribution

It provides novel experimental data on impact behavior in low gravity, showing that penetration depth scales with velocity but not gravity, and that impact regimes shift at lower energies.

## Key findings

- Penetration depth scales linearly with impact velocity.
- Collision duration is independent of gravity and velocity.
- Impacts in low gravity show no rebounds and transition to inertial regime at lower energies.

## Abstract

In order to improve our understanding of landing on small bodies and of asteroid evolution, we use our novel drop tower facility to perform low-velocity (2-40 cm s^-1), shallow impact experiments of a 10 cm diameter aluminum sphere into quartz sand in low effective gravities (~0.2-1 m s^-2). Using in situ accelerometers, we measure the acceleration profile during the impacts and determine the peak accelerations, collision durations and maximum penetration depth. We find that the penetration depth scales linearly with the collision velocity but is independent of the effective gravity for the experimental range tested, and that the collision duration is independent of both the effective gravity and the collision velocity. No rebounds are observed in any of the experiments. Our low-gravity experimental results indicate that the transition from the quasi-static regime to the inertial regime occurs for impact energies two orders of magnitude smaller than in similar impact experiments under terrestrial gravity. The lower energy regime change may be due to the increased hydrodynamic drag of the surface material in our experiments, but may also support the notion that the quasi-static regime reduces as the effective gravity becomes lower.