We still have very limited knowledge of the elemental composition of giant planets. Our best example is currently Jupiter, thanks to Galileo’s end-of-mission plunge into its atmosphere. Surprisingly, all elements (bar oxygen, whose depletion was probably due to especially dry local conditions) are enriched with respect to solar values by approximately the same amount — about a factor of three. This shouldn’t happen if Jupiter were accreted around its current location (~5 au): only some elements (sulfur, phosphorus and possibly carbon) would have been in the solid phase in the solar nebula, whereas others (nitrogen and the noble gases) would have still been volatile and would have dispersed. Among the proposed solutions to this puzzle, the idea that Jupiter’s core was formed further out in the Solar System, where nitrogen and various noble gases were frozen and could accrete, is gaining ground in theoretical and observational studies. Karin Öberg and Robin Wordsworth find that the enrichment pattern can indeed be explained if Jupiter’s core formed beyond ~30 au.
November 6, 2019