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

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.3

Bennu’s near-Earth lifetime of 1.75 million years inferred from craters on its boulders

“…Furthermore, the intercept of that curve will provide the value of P once 0 is calculated. Laboratory impact experiments have shown that cratering efficiency may increase when the size of the crater becomes comparable to the target boulder size [45]; however, this is thought to be due to spallation, which is not a dominant mechanism for the craters we observe on Bennu's surface.…”

Crater shape as a possible record of the impact environment of metallic bodies: Effects of temperature, impact velocity and impactor density

“…The Gibeon blocks in this study are small compared to the crater size. For brittle targets, the tensile strength is much lower than compressive or shear strength; therefore, when the target is small, the rarefaction waves generated at the free surface affect the spall diameter and total crater volume, with the topographic profile of the central pit being unaffected (Suzuki et al, 2018).…”

Effect of projectile shape and interior structure on crater size in strength regime

“…Note that spallation in porous gypsum targets often produces large fragments (e.g., Fig. 3 in Suzuki et al 2018). Such a process with large crack propagation is highly probabilistic; hence, the surface (spall) diameter D s /D p for porous gypsum may scatter.…”