PREPRINT
FC55CB45-F27F-4EA6-83F3-967121379439

# Amorphous ice in comets: evidence and consequences

Dina Prialnik and David Jewitt

Submitted on 13 September 2022

## Abstract

Ice naturally forms in the disordered or amorphous'' state when accreted from vapor at temperatures and pressures found in the interstellar medium and in the frigid, low density outer regions of the Sun's protoplanetary disk. It is therefore the expected form of ice in comets and other primitive bodies that have escaped substantial heating since formation. Despite expectations, however, the observational evidence for amorphous ice in comets remains largely indirect. This is both because the spectral features of amorphous ice are subtle and because the solar system objects for which we possess high quality data are mostly too close to the Sun and too hot for amorphous ice to survive near the surface, where it can be detected. This chapter reviews the properties of amorphous ice, the evidence for its existence and its consequences for the behavior of comets.

## Preprint

Subject: Astrophysics - Earth and Planetary Astrophysics