# Contacts of Water Ice in Protoplanetary Disks - Laboratory Experiments

## TL;DR

This study investigates how water ice grains stick and roll at various temperatures, revealing a significant increase in surface energy around 175-200 K, which impacts planetesimal formation in protoplanetary disks.

## Contribution

The paper provides experimental measurements of water ice grain sticking properties and surface energy variations at different temperatures relevant to protoplanetary disks.

## Key findings

- Sticking increases sharply between 175 K and 200 K.
- Surface energy rises by a factor of 63.4 within this temperature range.
- Water ice does not have a significant advantage over silicates for collisional growth.

## Abstract

Water ice is abundant in protoplanetary disks. Its sticking properties are therefore important during phases of collisional growth. In this work, we study the sticking and rolling of 1.1 mm ice grains at different temperatures. We find a strong increase in sticking between 175 K to 200 K which levels off at higher temperatures. In terms of surface energy this is an increase with a factor of 63.4, e.g. from $\gamma = 0.0029 \rm J/m^2$ to $\gamma = \rm 0.19 J/m^2$, respectively. We also measured critical forces for inelastic rolling. The critical rolling distance is constant with a value of 0.19 mm. In view of planetesimal formation at low temperatures in protoplanetary disks, the surface energy is not larger than for silicate dust and ice aggregation will share the same shortcommings. In general, water ice has no advantage over silicates for sticking and collisional growth might not favor ice over silicates.