Twin Worlds, Divergent Fates: How Obliquity has differently shaped Pluto's and Triton's landscapes and climates

TL;DR

This study uses long-term volatile transport simulations to show that obliquity differences primarily explain the contrasting surface features and climates of Pluto and Triton, supporting their shared origin with divergent evolutionary paths.

Contribution

The paper demonstrates through simulations that obliquity is the key factor causing the different surface and climate characteristics of Pluto and Triton, despite their similar origins.

Findings

Obliquity drives surface and climate differences.

Tidal heating affects Triton's surface.

Simulations match observed ice distributions.

Abstract

Triton and Pluto are believed to share a common origin, both forming initially in the Kuiper Belt but Triton being later captured by Neptune. Both objects display similar sizes, densities, and atmospheric and surface ice composition, with the presence of volatile ices N2, CH4 and CO. Yet their appearance, including their surface albedo and ice distribution strongly differ. What can explain these different appearances? A first disparity is that Triton is experiencing significant tidal heating due to its orbit around Neptune, with subsequent resurfacing and a relatively flat surface, while Pluto is not tidally activated and displays a pronounced topography. Here we present long-term volatile transport simulations of Pluto and Triton, using the same initial conditions and volatile inventory, but with the known orbit and rotation of each object. The model reproduces, to first order, the observed volatile ice surface distribution on Pluto and Triton. Our results unambiguously demonstrate that obliquity is the main driver of the differences in surface appearance and in climate properties on Pluto and Triton, and give further support to the hypothesis that both objects had a common origin followed by a different dynamical history.