Super-adiabatic Temperature Gradient at Jupiter's Equatorial Zone and Implications for the Water Abundance

Abstract

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 5$\mu$m hot spots with small but definite local departures from adiabaticity. We analyze Juno's microwave observations near Jupiter's equator (0 ~ 5${}^o$N) 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.

46 pages, 11 figures, accepted by Icraus

References in corpus (8)

• The water abundance in Jupiter's equatorial zone
• Condensation-inhibited convection in hydrogen-rich atmospheres: Stability against double-diffusive processes and thermal profiles for Jupiter, Saturn, Uranus, and Neptune
• Revelations on Jupiter's Formation, Evolution and Interior: Challenges from Juno Results
• Jupiter's Ammonia Distribution Derived from VLA Maps at 3--37 GHz
• Simulating Non-hydrostatic atmospheres on Planets (SNAP): formulation, validation and application to the Jovian atmosphere
• Longitude-resolved imaging of Jupiter at lambda = 2 cm
• A subsolar oxygen abundance or a radiative region deep in Jupiter revealed by thermochemical modelling
• Constraints on the latitudinal profile of Jupiter's deep jets

Cited by in corpus (1)

• GASTLI: An open-source coupled interior-atmosphere model to unveil gas giant composition