Noble gas enrichment in the Jovian atmosphere via disk photoevaporation

Abstract

Context. The Galileo probe has revealed that noble gas abundances (Ar, Kr, Xe) in the Jovian atmosphere are two to three times higher than the solar value. As the composition of the Jovian atmosphere was previously assumed be the same as the solar value, the origin of this heightened proportion remains a mystery. Prior studies have suggested that disk photoevaporation could explain the enrichment; however, their methods did not incorporate the effects of sublimation and condensation for noble gases. Aims. We aim to explain the enrichment of noble gases in the Jovian atmosphere, considering the sublimation and recondensation of each noble gas, along with disk photoevaporation and radial dust transport. Methods. We solved a one-dimensional diffusion equation for the disk gas from the infall stage, incorporating internal and external photoevaporation. We also solved the advection and diffusion equations for the dust and noble gases. We focused on models with the capacity to reproduce the global characteristics of the early solar system, namely, the disappearance of the disk after 4–6 Myr and the formation of planetesimals at two locations. Results. When noble gases are trapped only on the surface of amorphous ice, it is believed that argon, krypton, and xenon are released from cold dust grains in the protosolar disk at temperatures between 19 and 35 K. Our models generally lead to a very inefficient trapping and near-solar abundances in Jupiter, incompatible with the constraints. However, recent laboratory experiments using amorphous ice trapping, the noble gases inside yielded significantly higher desorption energies, resulting in the release of noble gases between 40 and 50 K. Finally, we find that the lower mass-loss rate attributed to disk photoevaporation is sufficient to reproduce the noble gas enrichment.