Centroid migration on an impacted granular slope due to asymmetric ejecta deposition and landsliding

TL;DR

This study investigates how asymmetric ejecta deposition and landsliding cause centroid migration on inclined granular slopes after impacts, providing a quantitative model relevant for planetary terrain analysis.

Contribution

The paper introduces a new quantitative model for centroid migration due to asymmetric cratering on inclined granular surfaces, validated through experiments.

Findings

Centroid migration depends on initial slope and ejecta asymmetry.

The model accurately predicts centroid displacement with specific parameters.

Results are consistent with previous studies on ejecta effects.

Abstract

For a fundamental understanding of terrain relaxation occurring on sloped surfaces of terrestrial bodies, we analyze the crater shape produced by an impact on an inclined granular (dry-sand) layer. Owing to asymmetric ejecta deposition followed by landsliding, the slope of the impacted inclined surface can be relaxed. Using the experimental results of a solid projectile impact on an inclined dry-sand layer, we measure the distance of centroid migration induced by asymmetric cratering. We find that the centroid migration distance $x_\mathrm{mig}$ normalized to the crater minor-axis diameter $D_\mathrm{cy}$ can be expressed as a function of the initial inclination of the target $\tan\theta$, the effective friction coefficient $\mu$, and two parameters $K$ and $c$ that characterize the asymmetric ejecta deposition and oblique impact effect: $x_\mathrm{mig}/D_\mathrm{cy}=K \tan\theta/(1-(\tan\theta/\mu)^2)+c$, where $K=0.6$, $\mu=0.8$, and $c=-0.1$ to $0.3$. This result is consistent with a previous study that considered the effect of asymmetric ejecta deposition. The obtained results provide fundamental information for analyzing the degradation of sloped terrain on planetary surfaces, such as crater-shape degradation due to the accumulation of micro-impacts.