Triton and Pluto: same origin but separated at birth

TL;DR

This paper reviews the formation conditions of Pluto and Triton, suggesting they originated from similar regions in the protosolar nebula based on their volatile contents and compositional links with certain comets.

Contribution

It provides a comparative analysis of Pluto and Triton's formation environments, highlighting their potential common origin and the implications for Solar System formation theories.

Findings

Pluto and Triton likely accreted material from near CO and N2 icelines.

Comet C/2016 R2 shares compositional features with Pluto and Triton.

Triton's formation in Neptune's disk implies early formation in the nebula.

Abstract

Assessing the origin of Pluto and Triton has profound implications for the bigger picture of Solar System formation and evolution. In such a context, this chapter reviews our current knowledge of the formation conditions of Pluto and Triton's constitutive building blocks in the protosolar nebula, which can be derived from their known or estimated volatile contents. Assuming that the ultravolatiles carbon monoxide and dinitrogen detected in Pluto and Triton are primordial, the presence of these molecules suggest that the two bodies accreted material originating from the vicinity of the carbon monoxide and dinitrogen icelines. Dinitrogen--rich and water--poor comets such as comet C/2016 R2 (PanSTARRS) obviously present a compositional link with Pluto and Triton, indicating that their building blocks formed in nearby regions of the protosolar nebula, despite of the variation of the water abundance among those bodies. Also, the assumption of Triton's growth in Neptune's circumplanetary disk requires that its building blocks formed at earlier epochs in the protosolar nebula, to remain consistent with its estimated composition.