Analysis of pit craters on asteroids and small bodies: Predictions about the regolith layer and internal structure

Abstract

In this work, we investigate and compare potential features called pit craters on the surfaces of (951) Gaspra, (243) Ida, (433) Eros, and the Martian moon, Phobos. Pit craters are typically arranges as chains on the surface and appear to be formed by the drainage of overlying loose material into internal voids promoted by fractures, assessing a piece of direct information about the approximate thickness of the regolith layer, and the internal configuration of each small body. Methodologically, we analyzed images taken by Galileo, NEAR Shoemaker, and other Martian rendezvous missions and mapped these geological morphologies across their surfaces. We analyzed pit sizes using Analysis of Variance and looked for correlations in terms of their different intrinsic physical properties. The pit sizes range between 0.034 and 0.971 km and their estimated regolith layers between 100 and 300 m thick for the four bodies. We demonstrated a strong correlation between the mean diameter of these depressions and the density of the body, making possible a linear model to predict the size of pit craters on small bodies to be visited in future missions, such as Deimos or asteroid (16) Psyche. We also proposed an internal fracturing index for these small bodies that shows a strong correlation with each mean body density. The data provided by future missions for different pitted small objects will allow us to validate or reject these models and predictions.