Ice Giants Revisited: Uranus and Neptune as Magma Ocean Worlds
2026/06/16 by Edward D. Young, Sarah P. Marcum, Aaron Werlen +1 · 6 voices
#astro-ph.EP
paper · pdf
Abstract
Uranus and Neptune are commonly interpreted as volatile-rich "ice giants", an assumption that underpins most interior models. Here we show that their observed radii, bulk densities, gravitational harmonics, normalized moments of inertia, intrinsic luminosities, and key features of their atmospheric compositions are consistent with interiors comprising supercritical, hydrogen-rich magma oceans overlain by H2-rich envelopes. Our results, based on three fit parameters for each planet, provide a parsimonious explanation for the structures, thermal states, and atmospheric chemistries of Uranus and Neptune. We find that the Solar System's ice giants are better understood as magma-ocean giants, with origins parallel to those of sub-Neptune gas-dwarf planets. A continuum among gas dwarf planets permits Neptune and Uranus to serve as accessible, data-driven test cases for structure models and material properties used to understand sub-Neptunes.
Discussions
- New theoretical study of possible interiors of Uranus and Neptune, though the authors admit "magma" is a fraught term in this context (but props for ~correct colors to illustrate U&N outer atmospheres [bsky, 44 points, 3 comments]
- Gee, Neptune! How come your mom lets you have your magma ocean on the inside? arxiv.org/abs/2606.18219 [bsky, 27 points, 1 comments]
- friendship ended with ice giants ❄️🙅 magma ocean giants are my new best friends 🌋🫶 [bsky, 12 points, 0 comments]
- 😲 Up is down, war is peace, and the ice giants are now magma ocean worlds! 😉 But wow, that would be very interesting! 🪐 [bsky, 11 points, 0 comments]
- 🪐 Et si Uranus et Neptune n'étaient pas des géantes glacées, mais étaient plutôt composées d'un océan de magma entouré d'une épaisse couche de dihydrogène ? C'est le modèle que propose ce papier, qui [bsky, 5 points, 0 comments]
- Enstatite + Iron + H2 "supercritical magma ocean" is what's being called for here. [bsky, 1 points, 1 comments]
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