Double-diffusive Erosion of the Core of Jupiter

Abstract

We present direct numerical simulations of the transport of heat and heavy elements across a double-diffusive interface or a double-diffusive staircase, in conditions that are close to those one might expect to find near the boundary between the heavy-element-rich core and the hydrogen–helium envelope of giant planets such as Jupiter. We find that the nondimensional ratio of the buoyancy flux associated with heavy-element transport to the buoyancy flux associated with heat transport lies roughly between 0.5 and 1, which is much larger than previous estimates derived by analogy with geophysical double-diffusive convection. Using these results in combination with a core erosion model proposed by Guillot et al., we find that the entire core of Jupiter would be eroded within less than 1 Myr, assuming that the core–envelope boundary is composed of a single interface. We also propose an alternative model that is more appropriate in the presence of a well-established double-diffusive staircase, and find that in this limit a large fraction of the core could be preserved. These findings are interesting in the context of Juno ’s recent results, but call for further modeling efforts to better understand the process of core erosion from first principles.