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A diffuse core in Saturn revealed by ring seismology

Mankovich, Christopher R. and Fuller, Jim (2021) A diffuse core in Saturn revealed by ring seismology. Nature Astronomy, 5 (11). pp. 1103-1109. ISSN 2397-3366. doi:10.1038/s41550-021-01448-3.

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[img] PDF (Supplementary Figs. 1 and 2 and Discussion) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 1: Comparison of assumed shapes for Saturn’s composition gradient) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 2: Eigenfunctions of m = − 2, l = 2 pseudomodes in Saturn) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 3: Eigenfunctions of m = − 2, l = 2 pseudomodes as a function of the width of the g mode cavity) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 4: Relationship between ice to rock mass fraction, fice, and predicted central heavy element mass fraction (ice plus rock), Zin) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 5: Effect of superadiabatic thermal stratification) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 6: Results of seismology/gravity retrievals for different parameterizations of Saturn’s interior structure) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 7: Effect of deep zonal winds on sectoral mode frequencies) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 8: Saturn’s m = − 2 mode spectrum including coupling across pseudomodes of different l) - Supplemental Material
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The best constraints on the internal structures of giant planets have historically originated from measurements of their gravity fields. These data are inherently mostly sensitive to a planet’s outer regions, stymieing efforts to measure the mass and compactness of the cores of Jupiter and Saturn. However, studies of Saturn’s rings have detected waves driven by pulsation modes within the planet, offering independent seismic probes of Saturn’s interior. The observations reveal gravity-mode pulsations, which indicate that part of Saturn’s deep interior is stable against convection. Here, we compare structural models with gravity and seismic measurements from Cassini to show that the data can only be explained by a diffuse, stably stratified core–envelope transition region in Saturn extending to approximately 60% of the planet’s radius and containing approximately 17 Earth masses of ice and rock. This gradual distribution of heavy elements constrains mixing processes at work in Saturn, and it may reflect the planet’s primordial structure and accretion history.

Item Type:Article
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URLURL TypeDescription ReadCube access Paper ItemCode
Mankovich, Christopher R.0000-0002-4940-9929
Fuller, Jim0000-0002-4544-0750
Additional Information:© The Author(s), under exclusive licence to Springer Nature Limited 2021. Received 08 February 2021; Accepted 09 July 2021; Published 16 August 2021. C.R.M. thanks D. Stevenson for comments and the Juno Interiors Working Group for helpful discussions, and acknowledges support from the Division of Geological and Planetary Sciences at Caltech. J.F. is grateful for support through an Innovator Grant from The Rose Hills Foundation and through grant FG-2018-10515 from the Sloan Foundation. Data availability: A representative subset of the interior models generated in the course of this work is available upon request. Code availability: The planetary structure and ToF code used to create the planetary models is available at The oscillation code and ancillary code related to the analysis are available upon request. Author Contributions: C.R.M. developed the planetary models, performed the calculations and analysis and led the preparation of the manuscript. J.F. developed the original oscillation code, contributed to the interpretation of the results and helped to write the manuscript. The authors declare no competing interests. Peer review information: Nature Astronomy thanks Mark Marley and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Caltech Division of Geological and Planetary SciencesUNSPECIFIED
Rose Hills FoundationUNSPECIFIED
Alfred P. Sloan FoundationFG-2018-10515
Subject Keywords:Giant planets; Seismology
Issue or Number:11
Record Number:CaltechAUTHORS:20210526-113349323
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Official Citation:Mankovich, C.R., Fuller, J. A diffuse core in Saturn revealed by ring seismology. Nat Astron 5, 1103–1109 (2021).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109256
Deposited By: George Porter
Deposited On:26 May 2021 19:44
Last Modified:16 Nov 2021 17:05

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