Crater Statistics of Arrokoth and Pluto's Small Moons with Comparison to Other Inner and Outer Solar System Bodies Using the Small Body Mapping Tool (SBMT)

NASA's New Horizons mission visited both the Pluto-system and the ~35-km-length cold classical Kuiper belt object (KBO) Arrokoth. These flybys revealed the detailed shapes and surfaces of these KBOs for the first time. We have integrated the most up-to-date shape models of Arrokoth and Pluto's ~40-km-diameter moons Nix and Hydra into the John's Hopkins Applied Physics Laboratory Small Body Mapping Tool (SBMT; Ernst et al., 2018; sbmt.jhuapl.edu). In addition, we have projected the images and other data collected by New Horizons onto these shapes.

We will report results from analysis of this new data collection. Crater measurements were performed on the 3D surfaces and compared with those collected on the "flat", unprojected images. We also compare our new crater measurements to those for other small bodies in both the inner and outer solar system. We also undertook a study of the effects of lighting geometry and image resolution on the results. Our preliminary results confirm the relatively shallow size-frequency distribution slope found for the smaller craters on Arrokoth (a differential slope of approximately -2; Spencer et al., 2020; Singer et al., 2020). We also find a differential slope for all craters on the martian moon Phobos of -2.4 similar to some previous measurements (e.g., Basilevsky et al. 2014). We use Phobos as a comparison to Arrokoth because it is a somewhat similarly-sized object (~27x24x18 km) and it was imaged by the Mars Reconnaissance Orbiter High Resolution Imaging Experiment (MRO HiRISE) camera under similar lighting conditions to Arrokoth.

References:

Basilevsky, A.T., Lorenz, C.A., Shingareva, T.V., Head, J.W., Ramsley, K.R., Zubarev, A.E., 2014. The surface geology and geomorphology of Phobos. Planetary and Space Science 102, 95. doi:10.1016/j.pss.2014.04.013

Ernst C.M. et al., 2018. The Small Body Mapping Tool (SBMT) for Accessing, Visualizing, and Analyzing Spacecraft Data in Three Dimensions, LPSC 49, abstract no. 1043.

Singer, K.N., et al., 2020. Impact craters on 2014 MU69: Implications for Kuiper belt object size-frequency distributions and planetesimal formation. Am. Astron. Soc. Meet. Abstract no. 419.06.

Spencer, J.R., et al., 2020. The geology and geophysics of Kuiper belt object (486958) Arrokoth. Science 367, aay3999. doi:10.1126/science.aay3999