Thermal-orbital evolution of Eris

TL;DR

This study models Eris's thermal and spin-orbital evolution, showing that a subsurface ocean is likely necessary for its current dissipative state, with implications for its internal structure and thermal history.

Contribution

The paper introduces a coupled thermal and spin-orbital evolution model for Eris, demonstrating the importance of a subsurface ocean in its dissipative evolution.

Findings

Oceans are favored in 77-100% of models for Eris's evolution.

Without an ocean, Eris requires a warm, convecting ice shell with high dissipation.

Oceans tend to freeze over unless insulation or antifreeze agents are present.

Abstract

The large Kuiper Belt object (KBO) Eris is nearly as big as Pluto and has a small moon, Dysnomia. Constraints on the system's spin and orbit characteristics were recently used to argue for a dissipative Eris, requiring a differentiated structure but not necessarily a subsurface ocean. Here, we model the thermal history of Eris coupled to its spin-orbital evolution, finding a subsurface ocean is preferred in order for Eris to be sufficiently dissipative. Spinning down Eris without an ocean is difficult, requiring a warm convecting ice shell protected by a thick insulating layer and very dissipative anelastic behavior in ice. Oceans make up 77-100% of successful thermal-orbital evolution models, depending on the parameters assumed, which increases to >98% when the Andrade $\beta$ parameter for ice is restricted to $\beta\leq3\times10^{-11}$ Pa$^{-1}$ s$^{-0.25}$. Oceans freeze over by the present day unless insulation (porosity, gas clathrates) or antifreeze are present.