Axisymmetric landslides on small planetary bodies

TL;DR

This paper models how axisymmetric landslides influence the shape and rotation of small planetary bodies, revealing insights into asteroid shape evolution and rotational stability.

Contribution

It introduces a coupled model of landsliding and rotational dynamics, incorporating effects like gravity, shape change, and radiation torque, applied to asteroid evolution.

Findings

Landsliding redistributes regolith, preventing rotational fission.

Rapid formation of top-shaped asteroids explained by landsliding.

Model predicts shape and spin evolution of rubble asteroids over time.

Abstract

We aim to understand how landslides affect the shape and rotational motion of small rubble planetary bodies. We limit ourselves to axisymmetric global landslides, and take the primordial shape of the body to also be axisymmetric. The landslides are modeled through depth-averaging, while also incorporating the effect of the body's rotation, topographical changes due to multiple landslides, the body's non-uniform gravity field and possible surface mass shedding. The body's rotational dynamics is coupled to its shape change due to landsliding, and also includes the action of radiation torque. We utilize our model to investigate regolith motion on actual asteroids. We then study the evolution of the shape and spin state of an initially spherical rubble asteroid due to impact-induced global landsliding events over its lifetime. We find that rotational fission is suppressed by regolith redistribution to the body's equator by landsliding. Furthermore, top shapes are rapidly formed and this may explain the abundance of top-shaped asteroids in near-Earth orbits.