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Published November 17, 2023 | Published
Journal Article Open

The internal structure of Eris inferred from its spin and orbit evolution

  • 1. ROR icon California Institute of Technology


The large Kuiper Belt object Eris is tidally locked to its small companion Dysnomia. Recently obtained bounds on the mass of Dysnomia demonstrate that Eris must be unexpectedly dissipative for it to have despun over the age of the solar system. Here, we show that Eris must have differentiated into an ice shell and rocky core to explain the dissipation. We further demonstrate that Eris's ice shell must be convecting to be sufficiently dissipative, which distinguishes it from Pluto's conductive shell. The difference is likely due to Eris's apparent depletion in volatiles compared with Pluto, perhaps as the result of a more energetic impact.

Copyright and License

© 2023 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).


The authors received no funding for this work.


Conceptualization and methodology: F.N. Writing–original draft: F.N. Writing–review and editing: F.N. and M.E.B.

Data Availability

The code required to generate Figs. 1 and 2 and described in Materials and Methods is available in the UCSC Dryad repository at https://doi.org/10.7291/D18X0D. All data needed to evaluate the conclusions in the paper are present in the paper.

Conflict of Interest

The authors declare that they have no competing interests.


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Additional details

November 16, 2023
November 17, 2023