Asteroids, Comets, and Kuiper Belt Objects: Sources of Inner and Outer Solar System Crater Populations

The size-frequency distribution (SFD) of Solar System objects is diagnostic of the formational and collisional history of those objects. As smaller objects impact larger ones, craters form which can be used to infer the impactor population through the use of various scaling laws. The lunar crater population is well studied and forms the basis and model for inner solar system bodies, while near-Earth asteroids (NEAs) provide a present-day comparison population. Combined, these can be used to model the main asteroid belt's (MBA's) SFD. The outer solar system (OSS) likely underwent a distinct collision and dynamic history, which should be reflected in differences in the SFD of impact craters and small bodies that formed them. However, the OSS is much more difficult to observe: Many fewer spacecraft have imaged solid OSS surfaces, and ground- or near-Earth-based telescopic surveys of comet nuclei are much more difficult than asteroid surveys reaching down to the same size. Recent advances from telescopic have offered at least two independent estimates of the SFD of Jupiter-family comet (JFC) and short- and long-period comet (SPC, LPC) nuclei from the Kuiper Belt. Independently, NASA's New Horizons spacecraft in the past five years has provided unprecedented imaging of Pluto, Charon, their satellite Nix, and Kuiper Belt Object (KBO) Arrokoth that spatially resolved impact craters. The Pluto-Charon system provides an important crater population because the giant planets' satellite systems likely exchange material, such that their crater populations are likely contaminated by planetocentric impactors. This work seeks to answer two very broad questions: Given these recent surveys and spacecraft data, \underline{(1) is there convincing evidence for distinct inner and outer solar system impactor populations, and (2) is there convincing evidence that the cometary SFD is the source of OSS impact craters?} At the COSPAR meeting in August, we will present progress on this work based on an analysis of published impact crater catalogs, comet surveys, asteroid models, and implementation of scaling laws. While we acknowledge that the questions we seek to answer are generally thought to have been answered (though parts of the comet community and crater community still do not fully agree), this method of analyzing the data has not been done, and many of the datasets we can use to compare have only just been made available.