Timescale of asteroid resurfacing by regolith convection resulting from the impact-induced global seismic shaking

TL;DR

This paper develops a model to estimate the timescale of asteroid surface renewal via regolith convection driven by impact-induced seismic shaking, suggesting it could be a feasible resurfacing mechanism within typical asteroid lifetimes.

Contribution

It introduces a new model linking impact seismic shaking to regolith convection and estimates the resurfacing timescale considering parameter uncertainties.

Findings

Resurfacing timescale is shorter than asteroid collisional lifetime in most cases.

Regolith convection could be a viable asteroid resurfacing process.

Parameter dependence analysis clarifies conditions for effective resurfacing.

Abstract

A model for the asteroid resurfacing by regolith convection is built to estimate its timescale. In the model, regolith convection is driven by the impact-induced global seismic shaking. The model consists of three steps: (i) intermittent impact of meteoroids, (ii) impact-induced global vibration (seismic shaking), and (iii) vibration-induced regolith convection. In order to assess the feasibility of the resurfacing process driven by regolith convection, we estimate the resurfacing timescale as a function of the size of a target asteroid. In the estimate, a set of parameter values is assumed on the basis of previous works. However, some of them (e.g., seismic quality factor $Q$, seismic efficiency $\eta$, and seismic frequency $f$) are very uncertain. Although these parameter values might depend on asteroid size, we employ the standard values to estimate the representative behavior. To clarify the parameter dependences, we develop an approximated scaling form for the resurfacing timescale. According to the estimated result, we find that the regolith-convection-based resurfacing timescale is shorter than the mean collisional lifetime in most of the parameter uncertainty ranges. These parameter ranges are within those reported by previous works for small asteroids. This means that the regolith convection can be a possible mechanism for the asteroid resurfacing process.