Abstract
We aim at investigating whether the chemical composition of the outer region of the protosolar nebula can be consistent with current estimates of the elemental abundances in the ice giants. To do so, we use a self-consistent evolutionary disc and transport model to investigate the time and radial distributions of H2O, CO, CO2, CH3OH, CH4, N2 and H2S, i.e. the main O-, C-, N and S-bearing volatiles in the outer disc. We show that it is impossible to accrete a mixture composed of gas and solids from the disc with a C/H ratio presenting enrichments comparable to the measurements (approx. 70 times protosolar). We also find that the C/N and C/S ratios measured in Uranus and Neptune are compatible with those acquired by building blocks agglomerated from solids condensed in the 10-20 arb. units region of the protosolar nebula. By contrast, the presence of protosolar C/N and C/S ratios in Uranus and Neptune would imply that their building blocks agglomerated from particles condensed at larger heliocentric distances. Our study outlines the importance of measuring the elemental abundances in the ice giant atmospheres, as they can be used to trace the planetary formation location, the origin of their building blocks and/or the chemical and physical conditions of the protosolar nebula. This article is part of a discussion meeting issue 'Future exploration of ice giant systems'.
Highlights
Uranus and Neptune are the outermost giant planets of our solar system
In this work, assuming the carbon abundances determined in the atmospheres of Uranus and Neptune are representative of their bulk composition, we have shown that it is impossible to accrete a mixture composed of gas and solids from the PSN with a C/H ratio presenting enrichments comparable to the measurements (∼70 times protosolar)
We found that the C/N and C/S ratios in Uranus and Neptune are compatible with those acquired by grains condensed in the vicinities of N2 and CO ice lines in the PSN
Summary
Uranus and Neptune are the outermost giant planets of our solar system. The apparent size of these two planets in the sky is roughly a factor of 10 smaller than Jupiter and Saturn, making their physical properties much more difficult to characterize. Often models assume a large region of the planet presenting high volatiles enrichments [3,4,5,6] This is supported by the measurement of the C abundance, found to be enriched ∼70 times its protosolar value in both planets (see Table 1), but recent measurements suggest that N/H and S/H ratios might be instead subsolar in their envelopes [7,8], unless hidden reservoirs of nitrogen and sulfur exist at deeper levels [9,10].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
