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 because 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 hot spots with small but definite local departures from adiabaticity. We analyze Juno’s microwave observations near Jupiter’s equator (0 ~ 5 oN) 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 times solar with a possible range of 2 ~ 7 times solar in Jupiter’s equatorial region.

Authors 17

1. Cheng Li corresponding

   University of Michigan

   Affiliation as printed

   University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, United States of America

2. Michael Allison

   Columbia University

   Affiliation as printed

   Columbia University, New York, NY, USA

3. S. K. Atreya

   University of Michigan

   Affiliation as printed

   University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, United States of America

4. Leigh N. Fletcher corresponding

   University of Leicester

   Affiliation as printed

   School of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK

5. Andrew P. Ingersoll

   California Institute of Technology

   Affiliation as printed

   California Institute of Technology

6. Tristan Guillot corresponding

   Observatoire de la Côte d’Azur

   Affiliation as printed

   Observatoire de la Côte d'Azur, France

7. Liming Li

   University of Houston

   Affiliation as printed

   University of Houston, USA

8. Jonathan I. Lunine

   Cornell University

   Affiliation as printed

   Department of Astronomy, Cornell University, USA

9. Yamila Miguel corresponding Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands

10. G. S. Orton corresponding

    Jet Propulsion Laboratory

    Affiliation as printed

    Jet Propulsion Laboratory, California Institute of Technology, USA

11. Fabiano Oyafuso

    Jet Propulsion Laboratory

    Affiliation as printed

    Jet Propulsion Laboratory, California Institute of Technology, USA

12. Paul G. Steffes

    Georgia Institute of Technology

    Affiliation as printed

    Georgia Institute of Technology, USA

13. Hunter Waite corresponding
    Affiliation as printed

    Waite Science LLC, USA

14. Michael H. Wong

    Search for Extraterrestrial Intelligence

    Affiliation as printed

    SETI Institute, USA

15. Zhimeng Zhang corresponding

    Jet Propulsion Laboratory

    Affiliation as printed

    Jet Propulsion Laboratory, California Institute of Technology, USA

16. S. Levin corresponding

    Jet Propulsion Laboratory

    Affiliation as printed

    Jet Propulsion Laboratory, California Institute of Technology, USA

17. S. J. Bolton

    Southwest Research Institute

    Affiliation as printed

    Southwest Research Institute, USA