# Are Pebble Pile Planetesimals Doomed?

## TL;DR

This study investigates wind erosion of granular beds under low gravity and pressure, confirming existing models and suggesting small pebble pile planetesimals in protoplanetary discs are unstable and prone to disassembly by wind forces.

## Contribution

It extends wind erosion models to lower gravity and pressure conditions relevant to planetesimals, providing experimental data on their stability in protoplanetary discs.

## Key findings

- Erosion thresholds are consistent with existing models at new low g and pressure conditions.
- Small pebble pile planetesimals are unstable and can be disassembled by wind in inner protoplanetary disc regions.
- Experimental parameters help reduce extrapolation uncertainties for planetary surface erosion models.

## Abstract

In parabolic flight experiments we studied the wind induced erosion of granular beds composed of spherical glass beads at low gravity and low ambient pressure. Varying g-levels were set by centrifugal forces. Expanding existing parameter sets to a pressure range between $p=300-1200\,$Pa and to g-levels of $g=1.1-2.2\,\rm m\,s^{-2}$ erosion thresholds are still consistent with the existing model for wind erosion on planetary surfaces by Shao & Lu (2000). These parameters were the lowest values that could technically be reached by the experiment. The experiments decrease the necessary range of extrapolation of erosion thresholds from verified to currently still unknown values at the conditions of planetesimals in protoplanetary discs. We apply our results to the stability of planetesimals. In inner regions of protoplanetary discs, pebble pile planetesimals below a certain size are not stable but will be disassembled by a head wind.