Collisions of solid ice in planetesimal formation

TL;DR

This study investigates collision behaviors of solid ice particles at various velocities, revealing conditions for mass transfer and fragmentation relevant to planetesimal formation near the snowline.

Contribution

It provides experimental data on ice collisions at different velocities, highlighting mass transfer thresholds and fragmentation behavior crucial for understanding planetesimal growth.

Findings

Mass transfer occurs up to a velocity-dependent threshold.

Smaller fragments can transfer mass to larger targets.

Threshold velocities for fragmentation and restitution are identified.

Abstract

We present collision experiments of centimetre projectiles on to decimetre targets, both made up of solid ice, at velocities of $15\,\mathrm{m\,s^{-1}}$ to $45\,\mathrm{m\,s^{-1}}$ at an average temperature of $\mathrm{T_{avg}}=255.8\pm0.7\,\mathrm{K}$. In these collisions the centimetre body gets disrupted and part of it sticks to the target. This behaviour can be observed up to an upper threshold, that depends on the projectile size, beyond which there is no mass transfer. In collisions of small particles, as produced by the disruption of the centimetre projectiles, we also find mass transfer to the target. In this way the larger body can gain mass, although the efficiency of the initial mass transfer is rather low. These collision results can be applied to planetesimal formation near the snowline, where evaporation and condensation is expected to produce solid ice. In free fall collisions at velocities up to about $7\,\mathrm{m\,s^{-1}}$, we investigated the threshold to fragmentation and coefficient of restitution of centimetre ice spheres.