Jupiter formed as a pebble pile around the N2 ice line

Abstract

Context. The region around the H2O ice line, due to its higher surface density, seems to be the ideal location to form planets. The core of Jupiter, as well as the cores of close-in gas giants are therefore thought to form in this region of the disk. Nevertheless, constraining the formation location of individual planets has proven to be difficult. Aims. We aim to use the nitrogen abundance in Jupiter, which is around four times solar, in combination with Juno constraints on the total mass of heavy elements in Jupiter to narrow down its formation scenario. Methods. Different pathways of enrichment of the atmosphere of Jupiter are considered, such as the accretion of enriched gas, pebbles, and planetesimals, and their implications for the oxygen abundance of Jupiter are discussed. Results. The super-solar nitrogen abundance in Jupiter necessitates the accretion of extra N2 from the proto-solar nebula. The only location of the disk where this can happen is outside or just inside the N2 ice line. These constraints favor a pebble accretion origin of Jupiter, from the perspective of composition and planet formation. We predict that Jupiter’s oxygen abundance is between 3.6 and 4.5 times solar.