Super-adiabatic Temperature Gradient at Jupiter’s Equatorial Zone and Implications For Water Abundance

By Keith Cowing
Status Report
March 12, 2024
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Super-adiabatic Temperature Gradient at Jupiter’s Equatorial Zone and Implications For Water Abundance
(A) Three idealized Jovian thermal models, dry adiabatic (black), sub-adiabatic (orange) and super-adiabatic (blue). The non-adiabatic temperature gradient is ± 0.15 �/km. The grey dashed lines show the contribution functions of 10, 5.2, 2.6, and 1.25 GHz channels (from top to bottom). (B) Nadir brightness temperature anomalies at six Juno MWR channels. From top to bottom, they are at 22 GHz, 10 GHz, 5.2 GHz, 2.6 GHz, 1.25 GHz, and 0.6 GHz, respectively. The horizontal error bars show a conservative 2% uncertainty. The contribution 5 functions for 22 GHz and 0.6 GHz peak at pressures outside the range of the graph. (C) Limbdarkening anomalies (evaluated at a 45-degree emission angle). The horizontal error bars show a 0.1% instrument noise level (Janssen et al., 2005, 2017). — astro-ph.EP

The temperature structure of a giant planet was traditionally thought to be an adiabat assuming convective mixing homogenizes entropy.

The only in-situ measurement made by the Galileo Probe detected a near-adiabatic temperature structure within one of Jupiter’s 5μm hot spots with small but definite local departures from adiabaticity. We analyze Juno’s microwave observations near Jupiter’s equator (0 ~ 5oN) and find that the equatorial temperature structure is best characterized by a stable super-adiabatic temperature profile rather than an adiabatic one.

Water is the only substance with sufficient abundance to alter the atmosphere’s mean molecular weight and prevent dynamic instability if a super-adiabatic temperature gradient exists. Thus, from the super-adiabaticity, our results indicate a water concentration (or the oxygen to hydrogen ratio) of about 4.9 times solar with a possible range of 1.5 ~ 8.3 times solar in Jupiter’s equatorial region.

Cheng Li, Michael Allison, Sushil Atreya, Shawn Brueshaber, Leigh N. Fletcher, Tristan Guillot, Liming Li, Jonathan Lunine, Yamila Miguel, Glenn Orton, Paul Steffes, J. Hunter Waite, Michael H. Wong, Steven Levin, Scott Bolton

Comments: 46 pages, 11 figures, accepted by Icraus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2403.05363 [astro-ph.EP] (or arXiv:2403.05363v1 [astro-ph.EP] for this version)
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Submission history
From: Cheng Li
[v1] Fri, 8 Mar 2024 14:52:22 UTC (5,988 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻