T46 Impact Cratering in Space and Time

Sunday, 9 October 2022
1:30 PM - 5:30 PM
501

EXPERIMENTAL IMPACTS INTO LAYERED TARGETS: IMPLICATIONS FOR THE MOON

Paper number: T46-3
Program: Technical Sessions
Time: 1:50 PM – 2:10 PM

Authors

Abstract

Impact craters provide clues about planetary surface properties. In the 1960s, for example, Oberbeck and Quaide experimentally demonstrated that crater morphology in the lunar maria reflected the thickness of a weaker regolith layer on top of its more competent, parent basalts. Small craters in the mare regions of the Moon commonly show a morphological progression from simple bowl-shapes to those with flat floors or central mounds, and finally to concentric structures as crater diameter increases. Using their experimental data and the transition diameters between these various crater forms in a given mare unit, Oberbeck and Quaide could then estimate the regolith thickness. This technique continues to be used today with even higher resolution images of the lunar surface (e.g., Bart et al., 2011; Bart, 2014).

The work presented here expands upon Oberbeck and Quaide’s pioneering experiments by examining laboratory-scale impacts into layered targets consisting of a loose sand over a bonded substrate. New analytical techniques allow us to derive quantitative data not only regarding the morphologies and morphometries of the craters formed in these targets, but also for the excavation-stage flow in the form of their ejecta curtains as these craters grow. In this study, we scan the resultant craters in three dimensions to obtain high-resolution topography; we also track ejected particles in flight to compare the excavation of craters in a layered target to those in a completely cohesionless one.

To apply our results to the Moon, co-author Bart was given the crater profiles from these experiments without knowing the true "regolith" thickness used for each target. She then applied her expertise in measuring regolith thicknesses on the Moon to determine the "regolith" thickness for each experiment. We will discuss her results and their implications for using this technique to estimate lunar regolith thicknesses. We will also examine the two different excavation-stage components observed during these experiments —central ejecta and curtain ejecta — and discuss their potential contributions to self-secondaries and boulders within and around small craters on the Moon.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-382847

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.