Rotation Reduces Convective Mixing in Jupiter and Other Gas Giants

Recent measurements of Jupiter’s gravitational moments by the Juno spacecraft and seismology of Saturn’s rings suggest that the primordial composition gradients in the deep interior of these planets have persisted since their formation. One possible explanation is the presence of a double-diffusive...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2023-06, Vol.950 (1), p.L4
Main Authors: Fuentes, J. R., Anders, Evan H., Cumming, Andrew, Hindman, Bradley W.
Format: Article
Language:English
Subjects:
Composition
Convection
Convective mixing
Energy flux
Entrainment
Gas giant planets
Hydrodynamic models
Jupiter
Jupiter probes
Kinetic energy
Planetary interior
Planetary rotation
Planets
Saturn
Saturn rings
Seismology
Solar system gas giant planets
Spacecraft
Staircases
Stellar convective zones
Velocity
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Summary:Recent measurements of Jupiter’s gravitational moments by the Juno spacecraft and seismology of Saturn’s rings suggest that the primordial composition gradients in the deep interior of these planets have persisted since their formation. One possible explanation is the presence of a double-diffusive staircase below the planet’s outer convection zone, which inhibits mixing across the deeper layers. However, hydrodynamic simulations have shown that these staircases are not long-lasting and can be disrupted by overshooting convection. In this Letter, we suggests that planetary rotation could be another factor for the longevity of primordial composition gradients. Using rotational mixing-length theory and 3D hydrodynamic simulations, we demonstrate that rotation significantly reduces both the convective velocity and the mixing of primordial composition gradients. In particular, for Jovian conditions at t ∼ 10 8 yr after formation, rotation reduces the convective velocity by a factor of 6, and in turn, the kinetic energy flux available for mixing gets reduced by a factor of 6 3 ∼ 200. This leads to an entrainment timescale that is more than 2 orders of magnitude longer than without rotation. We encourage future hydrodynamic models of Jupiter and other gas giants to include rapid rotation because the decrease in the mixing efficiency could explain why Jupiter and Saturn are not fully mixed.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/acd774