Further constraints on Jupiter's primordial structure

TL;DR

This study combines dynamical and thermal evolution models to constrain Jupiter's primordial structure, suggesting a warm, metal-rich dilute core and providing new insights into its formation and early evolution.

Contribution

It introduces a comprehensive modeling approach integrating dynamical constraints with thermal evolution to better understand Jupiter's primordial interior structure.

Findings

Jupiter's present structure is best explained by a warm, metal-rich dilute core.

The primordial radius of Jupiter is estimated to be approximately 1.89 R_J.

The envelope must have been significantly warmer at disk dispersal to match current spin constraints.

Abstract

The primordial structure of Jupiter remains uncertain, yet it holds vital clues on the planet's formation and early evolution. Recent work used dynamical constraints from Jupiter's inner moons to determine its primordial state, thereby providing a novel, formation-era anchor point for interior modeling. Building on this approach, we combine these dynamical constraints with thermal evolution simulations to investigate which primordial structures are consistent with present-day Jupiter. We present 4,250 evolutionary models of the planetary structure, including compositional mixing and helium phase separation, spanning a broad range of initial entropies and composition profiles. We find that Jupiter's present-day structure is best explained by a warm ($4.98_{-2.57}^{+3.00}\, \mathrm{k_B\, m_u^{-1}}$), metal-rich dilute core inherited from formation. To simultaneously satisfy constraints on Jupiter's primordial spin, however, its envelope must have been significantly warmer ($9.32_{-0.58}^{+0.48}\, \mathrm{k_B\, m_u^{-1}}$) at the time of disk dispersal. We determine Jupiter's primordial radius to be $1.89_{-0.49}^{+0.40}\, \mathrm{R_J}$. These results provide new constraints on Jupiter's formation, suggesting that most heavy elements were accreted early during runaway gas accretion, and placing bounds on the energy dissipated during the accretion shock.