Impact Craters on Pluto and Charon and Terrain Age Estimates

TL;DR

This study analyzes impact crater distributions on Pluto and Charon, revealing diverse terrain ages, evidence of geologic activity, and differences in impactor size-frequency distributions compared to the Moon.

Contribution

It provides new estimates of terrain ages and identifies a distinct size-frequency distribution break in craters, indicating differences in impactor populations.

Findings

Pluto's terrains range from no craters to heavily cratered, indicating varied ages.

Vulcan Planitia and northern Charon terrains are approximately 4 Ga or older.

Crater size-frequency distributions show a break at 10-15 km diameter, differing from lunar impactors.

Abstract

Pluto's terrains display a diversity of crater retention ages ranging from areas with no identifiable craters to heavily cratered terrains. This variation in crater densities is consistent with geologic activity occurring throughout Pluto's history and also a variety of resurfacing styles, including both exogenic and endogenic processes. Using estimates of impact flux and cratering rates over time, Pluto's heavily cratered terrains appear to be relatively ancient, 4 Ga or older. Charon's smooth plains, informally named Vulcan Planitia, did experience early resurfacing, but there is a relatively high spatial density of craters on Vulcan Planitia and almost all overprint the other types of volcanic or tectonic features. Both Vulcan Planitia and the northern terrains on Charon are also estimated to be ancient, 4 Ga or older. The craters on Pluto and Charon also show a distinct break in their size-frequency distributions (SFDs), where craters smaller than approximately 10-15 km in diameter have a shallower SFD power-law slope than those larger than this break diameter. This SFD shape on Pluto and Charon is different than what is observed on the Earth's Moon, and gives the Kuiper belt impactor SFD a different shape than that of the asteroid belt.