Dust release and tensile strength of the non-volatile layer of cometary nuclei

TL;DR

This paper presents a thermophysical model predicting dust release from cometary nuclei, emphasizing the role of CO2 ice at distances less than 3 AU, based on tensile strength and gas permeability data.

Contribution

It introduces a new model combining dust-aggregate collision physics with thermophysical properties to predict dust activity on comets, focusing on CO2 ice sublimation.

Findings

Dust release occurs for pure CO2 ice at <~3 AU.

Pure H2O ice cannot account for observed dust emissions.

The model links tensile strength and vapor pressure to dust activity.

Abstract

We developed a thermophysical model for cometary nuclei, which is based upon the assumption that comets form by the gravitational instability of an ensemble of dust and ice aggregates. Under this condition, the tensile strength of the ice-free outer layers of a cometary nucleus can be calculated, using the dust-aggregate collision and adhesion model of Weidling et al. (2011). Based on available laboratory data on the gas permeability and thermal conductivity of ice-free dust layers, we derived the temperature and pressure at the dust-ice interface for pure water and pure carbon dioxide ice. Comparison of the vapor pressure below the dust crust with its tensile strength allows the prediction of dust release from cometary surfaces. Our model predicts dust activity for pure CO2 ice and for heliocentric distances of <~ 3 AU, whereas pure H2O ice cannot explain the dust emission