A fresh examination of the Moon’s young craters: Insights from new datasets and analysis tools

Objectives: We propose to advance the state of understanding of the young lunar crater population by analyzing rayed and rocky craters and lunar “cold spots.” We will create a self-consistent, simple evolutionary model that accounts for both productionand destruction of rayed and rocky craters that simultaneously matches the observed spatial and temporal characteristics of both populations. We will use derived products from publicly released lunar datasets (LROC, LRO Diviner thermal radiometer, and Kaguya Lunar Multiband Imager) to investigate the nature and evolution of young craters; and we will employ state-of-the-art Bayesian inference tools to understand their respective spatial and age distributions. Finally, we will draw conclusions about the implications for the bombardment history of the lunar surface.

Background: Lunar crater rays, radial textural and/or albedo patterns reflecting disruption of the surface, can result from primary ejecta atop a contrasting substrate, stripping of a mature regolith layer, or mixing of immature regolith upward to the surface by subsequent impacts. Different ray varieties express themselves differently in remote sensing datasets, which can be used to quantify regolith maturity, composition, and thermal inertia. Separately, large rocks are ejected by impacts, and are detectable in thermal IR, radar, and image data.

Method: We will create a new comprehensive catalog of lunar rayed and rocky craters down to 2 km diameter within ±70o latitude using LRO camera and Kaguya MI reflectance, Kaguya derived optical maturity, Kaguya compositional maps, and Diviner H-parameter and rock abundance datasets. These catalogs include rays with fundamentally different physical properties, with craters showing different types of rays in different datasets. We will also verify and expand the current catalog of cold spots. We have completed a feasibility study that includes a partial catalog to 5 km diameter, leading to the following questions: a) Why are albedo rays notably concentrated at the equator, whereas thermophysical rays and rocky craters are not? b) Is the previously observed equatorial concentration of cold spots real? 2) Can we establish a single coherent model that accounts for production and destruction of both rocks and rays, and which reproduces our observations? 3) What are the implications for use of rocky and/or rayed craters as chronological markers?

We will approach these questions via four tasks:
Task 1) Establish the population of rayed and rocky craters with diameter ≥ 2 km;
Task 2) Quantify spatial and temporal properties of the database;
Task 3) Verify and expand cold spot database;
Task 4) Create a forward evolutionary model, satistfying all constraints from Tasks 1-3.

Impact: This work represents a timely re-examination of the nature and distribution of young craters, possible now with new data and Bayesian inference techniques. The results will shed new light on processes fundamentally important to lunar regolith evolution.