T109 Impact Cratering in the Solar System: Remembering Nadine Barlow and H. Jay Melosh

Monday, 11 October 2021
1:30 PM - 5:30 PM
Portland Ballroom 252 (Hybrid Room)

IMPACT RATE VARIATIONS OVER GEOLOGIC TIME: SPIKY OR SMOOTH?

Paper number: T109-2
Program: Technical Sessions
Time: 1:35 PM – 1:50 PM

Authors

Abstract

Models of crater production functions used to date terrains assume that the impact rate has been smooth (constant or slowly changing) over the past ~3 Ga; the sparse Apollo dates for lunar craters do not contradict that assumption [1]. However, impact rates must be variable (spiky) due to major collisions in the asteroid belt and from perturbations of Oort comets. How much uncertainty do these variations introduce to crater-count age estimates? The observational evidence for spikes ~480 [2] and ~800 [3] Ma ago have not been reproduced by independent studies, or may be explained by single impact events. However, evidence for an increased cratering rate in the inner solar system over the past ~300 Ma has now been reported from studies of lunar [4], terrestrial [5, but see 6], and martian [7] craters. This idea is supported by comparing dated lunar craters to a model of the incoming asteroid flux [8]. Evidence for a recent increase based on astronomical surveys [9, 10] and lunar impact glass spherules [11] remain debated. There is also both observational and theoretical evidence for a long-term decline in the cratering rate from 3 to 0.5 Ga [10, 12]. A new study indicates a remarkably constant rate of small meteorite delivery to Earth over past 500 Ma, except at 466 Ma [13]. But these particles would make very small (<1 m) lunar craters, whereas the evidence for variability comes from >10 km craters; the variability may be greater for larger impactors [14]. A new surge in lunar exploration including sample return and in-situ age dating promises to resolve these debates [15]. Given an assumption of constant cratering rate over the past 3 Ga, errors in the crater retention ages of planetary landscapes may be as large as a factor of two, which should be acknowledged in geologic interpretations.

[1] Hiesinger et al., 2012, JGR 117; [2] Schmitz et al., 2003, Science 300; [3] Terada et al., 2020, Nat. Comm.; [4] Mazrouei et al., 2019, Science 363; [5] Shoemaker, 1998, J. Royal Ast. Soc. Canada 92; [6] Hughes, 2000, MNRAS 317; [7] Lagain et al., 2020, PSS 180; [8] Marchi et al., 2009, Astron, J, 137; [9] Nesvorny and Roig, 2017, Astron J. 155; [10] Minton and Malhotra, 2010, Icarus 207; [11] Huang et al., 2018, GRL 45, [12] Culler et al., 2000, Science 287; [13] Terfelt and Schmitz, 2021, PNAS 118; [14] Kirchoff et al., 2021, Icarus 335; [15] Draper et al., 2021, PSJ 2.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-366541

© Copyright 2021 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.