Increase in cratering efficiency with target curvature in strength-controlled craters

TL;DR

This study demonstrates that target curvature significantly enhances cratering efficiency in strength-controlled impacts, leading to larger craters on small bodies, which challenges existing scaling laws that neglect curvature effects.

Contribution

The paper introduces experimental evidence showing how target curvature increases cratering efficiency, providing a new geometric perspective on impact processes on small celestial bodies.

Findings

Crater volume and radius increase with normalized curvature.

Pit dimensions remain constant regardless of curvature.

Curvature effects lead to larger craters than predicted by traditional models.

Abstract

Impact-cratering processes on small bodies are thought to be mainly controlled by the local material strength because of their low surface gravity, and craters that are as large as the parent bodies should be affected by the target curvature. Although cratering processes on planar surfaces in the strength-controlled regime have been studied extensively, the mechanism by which target curvature affects the cratering processes remains unclear. Herein, we report on a series of impact experiments that used spherical targets with various diameters. The resultant craters consisted of a deep circular pit and an irregular-shaped spall region around the pit, which is consistent with the features reported in a number of previous cratering experiments on planar surfaces. However, the volume and radius of the craters increased with the normalized curvature. The results indicate that the increase in the spall-region volume and radius mainly contributes to the increase in the whole crater volume and radius, although the volume, depth, and radius of pits remain constant with curvature. The results of our model indicate that the geometric effect due to curvature (i.e., whereby the distance from the equivalent center to the target free surface is shorter for higher curvature values) contributes to increases in the cratering efficiency. Our results suggest that the impactors that produce the largest craters (basins) on some asteroids are thus smaller than what is estimated by current scaling laws, which do not take into account the curvature effects.