Jupiter’s interior from Juno: Equation-of-state uncertainties and dilute core extent^★

¹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France
e-mail: saburo.howard@oca.eu
² Heidelberg Institute for Theoretical Studies (HITS gGmbH), Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
³ CITIES, NYUAD Institute, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, UAE
⁴ SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
⁵ Leiden Observatory, University of Leiden, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
⁶ Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
⁷ Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
⁸ Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁹ Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA
¹⁰ Institute for Computational Science, University of Zurich, Winterthurerstr. 190, CH8057 Zurich, Switzerland
¹¹ Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
¹² Institute of Planetary Research, German Aerospace Center, 12489 Berlin, Germany
¹³ Southwest Research Institute, San Antonio, TX 78238, USA

Received: 6 December 2022
Accepted: 6 February 2023

Abstract

Context. The Juno mission has provided measurements of Jupiter’s gravity field with an outstanding level of accuracy, leading to better constraints on the interior of the planet. Improving our knowledge of the internal structure of Jupiter is key to understanding its formation and evolution but is also important in the framework of exoplanet exploration.

Aims. In this study, we investigated the differences between the state-of-the-art equations of state and their impact on the properties of interior models. Accounting for uncertainty on the hydrogen and helium equation of state, we assessed the span of the interior features of Jupiter.

Methods. We carried out an extensive exploration of the parameter space and studied a wide range of interior models using Markov chain Monte Carlo simulations. To consider the uncertainty on the equation of state, we allowed for modifications of the equation of state in our calculations.

Results. Our models harbour a dilute core and indicate that Jupiter’s internal entropy is higher than what is usually assumed from the Galileo probe measurements. We obtain solutions with extended dilute cores, but contrary to other recent interior models of Jupiter, we also obtain models with small dilute cores. The dilute cores in such solutions extend to ~20% of Jupiter’s mass, leading to better agreement with formation–evolution models.

Conclusions. We conclude that the equations of state used in Jupiter models have a crucial effect on the inferred structure and composition. Further explorations of the behaviour of hydrogen–helium mixtures at the pressure and temperature conditions in Jupiter will help to constrain the interior of the planet, and therefore its origin.