Daniel Toledo – INTA – Madrid, Deep NH₃/H₂S Composition and the Coupling of NH₄SH and H₂S Clouds in the Ice Giants
Daniel Toledo – INTA – Madrid, Deep NH₃/H₂S Composition and the Coupling of NH₄SH and H₂S Clouds in the Ice Giants
Where: SwRI 4th Floor Seminar Room (white chairs) + webex (see details below)
Deep NH₃/H₂S Composition and the Coupling of NH₄SH and H₂S Clouds in the Ice Giants
Observations of Uranus and Neptune indicate the presence of H₂S clouds at pressures greater than ~2 bar, while thermochemical models predict the formation of NH₄SH clouds at deeper levels where NH₃ and H₂S react (~30–40 bar). The coupling between these cloud layers remains poorly understood, despite its importance for interpreting the vertical structure and composition of giant planet atmospheres.
In this presentation, we discuss results from an extended one-dimensional cloud microphysics model previously applied to simulate CH₄ and H₂S clouds in the Ice Giants. The model now incorporates NH₄SH chemistry, extending the simulation domain to deeper atmospheric levels (~40 bar). Since NH₃ reacts with H₂S to form NH₄SH at depth, the deep NH₃/H₂S ratio directly controls the amount of H₂S gas that can survive above the NH₄SH cloud layer and remain available to condense at higher altitudes.
We explore how the deep NH₃ and H₂S abundances, together with the vertical mixing profile, determine the properties of the observable H₂S cloud layer, including its base pressure, opacity, and particle size distribution. Under Ice Giant conditions, where deep H₂S abundances are expected to exceed those of NH₃, the formation of a deep NH₄SH cloud can still significantly deplete the upward transport of sulfur-bearing gas, indirectly modifying the structure of the upper H₂S cloud.
Finally, we discuss the contrasting regime expected in Jupiter and Saturn, where NH₃ is likely more abundant than H₂S, and how future observations, particularly radiometric measurements, could provide key constraints on the deep NH₃/H₂S composition through the study of cloud layers.
Location Details:
Hybrid – In person and Webex:
4th floor conference room at SwRI Boulder: (please see the 4th floor receptionist for a badge)
1301 Walnut St.
Boulder, CO
Webex: https://swri15.webex.com/meet/ksinger
Phone: 1-866-469-3239 Meeting Number: 2633 145 9127