Triggering Sublimation-Driven Activity of Main Belt Comets

TL;DR

This study uses impact simulations to assess whether collisions can expose sub-surface ice in Main Belt Comets, potentially triggering sublimation-driven activity, and finds impact-induced ice exposure is plausible within a few meters of the surface.

Contribution

The paper demonstrates through simulations that impacts can expose sub-surface ice in Main Belt Comets, supporting sublimation-driven activity as a viable mechanism.

Findings

Impact crater depth is slightly over 10 meters, exposing ice within a few meters of the surface.

Ice exposure occurs on crater interiors, bottoms, and ejected icy inclusions re-accreted on the surface.

Impact scenarios can explain MBC activity, suggesting higher initial water content in these objects.

Abstract

It has been suggested that the comet-like activity of Main Belt Comets are due to the sublimation of sub-surface water-ice that has been exposed as a result of their surfaces being impacted by m-sized bodies. We have examined the viability of this scenario by simulating impacts between m-sized and km-sized objects using a smooth particle hydrodynamics approach. Simulations have been carried out for different values of the impact velocity and impact angle as well as different target material and water-mass fraction. Results indicate that for the range of impact velocities corresponding to those in the asteroid belt, the depth of an impact crater is slightly larger than 10 m suggesting that if the activation of MBCs is due to the sublimation of sub-surface water-ice, this ice has to exist no deeper than a few meters from the surface. Results also show that ice-exposure occurs in the bottom and on the interior surface of impact craters as well as the surface of the target where some of the ejected icy inclusions are re-accreted. While our results demonstrate that the impact scenario is indeed a viable mechanism to expose ice and trigger the activity of MBCs, they also indicate that the activity of the current MBCs is likely due to ice sublimation from multiple impact sites and/or the water contents of these objects (and other asteroids in the outer asteroid belt) is larger than the 5% that is traditionally considered in models of terrestrial planet formation providing more ice for sublimation. We present details of our simulations and discuss their results and implications.