PF-02-0054

Ammonium salts in the solar nebula as the origin of Jupiter's nitrogen-enriched atmosphere

Kanon Nakazawa

Atmospheric compositions preserve the history of planet formation process. Jupiter has the remarkable feature of being uniformly enriched in various elements compared to the Sun, including highly volatile elements such as nitrogen and noble gases. Elemental transport by trapping volatiles in amorphous ice is one mechanism that explains Jupiter's composition. However, the low capture efficiency of nitrogen into amorphous ice prevents nitrogen enrichment of Jupiter.
We propose an alternative idea for transporting nitrogen to Jupiter: transport of ammonium salts by inward drifting dust. Ammonium salts, newly identified species in 67P/Churyumov-Gerasimenko, are candidates for compensating for the comet's nitrogen depletion compared to the Sun. We calculate the nitrogen abundance in the disk using global 1D simulations including the ammonium salts dissociation and test the feasibility of Jupiter’s nitrogen enrichment. We find that dust containing 10-30 wt% ammonium salts enhances the inner disk (r < 10 au) nitrogen abundance and a gas giant forming in the inner disk obtains a nitrogen-rich atmosphere similar to Jupiter's. Our results suggests that semi-volatile species such as salt may make a significant contribution to the atmospheric composition of planets.