Abstract
Recent structure models of Jupiter that match Juno gravity data suggest that the planet harbours an extended region in its deep interior that is enriched with heavy elements: a so-called dilute or fuzzy core. This finding raises the question of what possible formation pathways could have lead to such a structure. We modelled Jupiter’s formation and long-term evolution, starting at late-stage formation before runaway gas accretion. The formation scenarios we considered include both primordial composition gradients, as well as gradients that are built as proto-Jupiter rapidly acquires its gaseous envelope. We then followed Jupiter’s evolution as it cools down and contracts, with a particular focus on the energy and material transport in the interior. We find that none of the scenarios we consider lead to a fuzzy core that is compatible with interior structure models. In all the cases, most of Jupiter’s envelope becomes convective and fully mixed after a few million years at most. This is true even when we considered a case where the gas accretion leads to a cold planet, and large amounts of heavy elements are accreted. We therefore conclude that it is very challenging to explain Jupiter’s dilute core from standard formation models. We suggest that future works should consider more complex formation pathways as well as the modelling of additional physical processes that could lead to Jupiter’s current-state internal structure.
Highlights
The Juno mission (Bolton et al 2017) recently mapped Jupiter’s gravitational field with high precision (Folkner et al 2017; Iess et al 2018)
The same is true for the third profile Cold_high_Z, except that it begins with more heavy elements and accretes a much larger amount. We considered this model in order to explore a formation pathway that leads to significant accretion of heavy elements during runaway
Summary We calculated the formation and long-term evolution of Jupiter starting from the onset of runaway gas accretion until today, properly accounting for the energy transport and heavy-element mixing in the deep interior
Summary
The Juno mission (Bolton et al 2017) recently mapped Jupiter’s gravitational field with high precision (Folkner et al 2017; Iess et al 2018). Jupiter’s interior was modelled with a three-layer structure including: (i) a central compact icy and rocky core; (ii) an inner envelope of metallic hydrogen and helium; and (iii) an outer envelope of molecular hydrogen and helium These models typically assumed an adiabatic temperature profile for the planet, and the distribution of the heavy elements within the envelope(s) was assumed to be constant New interior structure models that fit the gravitational moments suggest that Jupiter has a dilute or fuzzy core, rather than a compact one (Wahl et al 2017; Debras & Chabrier 2019) This suggests that there is an extended region in the innermost part of the planet that is highly enriched with heavy elements. Diffusion of temperature is more efficient than that of composition, and the composition can be stably stratified
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