Formation, Composition, and History of the Pluto System: A Post-New-Horizons Synthesis

TL;DR

This paper synthesizes current knowledge on the formation, composition, and geological history of the Pluto system, highlighting its complex geology, active processes, and implications for planetary formation theories.

Contribution

It provides a comprehensive post-New Horizons synthesis of Pluto and Charon's formation, composition, and geological activity, emphasizing their complexity and significance for understanding dwarf planets.

Findings

Pluto's geological activity includes tectonism, cryovolcanism, and atmospheric processes.

Pluto's formation linked to early Solar System planetary migration.

Charon shows evidence of early tectonism and cryovolcanism.

Abstract

The Pluto-Charon system provides a broad variety of constraints on planetary formation, composition, chemistry, and evolution. Pluto was the first body to be discovered in what is now known as the Kuiper belt, its orbit ultimately becoming a major clue that the giant planets underwent substantial orbital migration early in Solar System history. This migration has been linked to an early instability in the orbits of the giant planets and the formation of the Kuiper belt itself, from an ancestral trans-Neptunian planetesimal disk that included Pluto. Pluto-Charon is emblematic of what are now recognized as small or dwarf planets. Far from being a cold, dead, battered icy relic, Pluto displays evidence of a complex geological history, with ongoing processes including tectonism, cryovolcanism, solid-state convection, glacial flow, atmospheric circulation, surface-atmosphere volatile exchange, aeolian processes, and atmospheric photochemistry, microphysics, and haze formation. Despite Pluto's relatively modest scale, the combination of original accretional heat, long-term internal radiogenic heat release, and external solar forcing, when combined with sufficiently volatile (and thus mobile) materials, yields an active world. Pluto may have inherited a large organic mass fraction during accretion, which may responsible, in part, for its surface and atmospheric volatiles. Charon, Pluto's major moon, displays evidence of extensive early tectonism and cryovolcanism. Dwarf planets are thus truly planetary in terms of satellite systems and geological and atmospheric complexity (if not ongoing activity). What they may lack in mass is made up in number, and the majority of the Solar System's dwarf planets remain undiscovered.