Models of Saturn's Interior Constructed with an Accelerated Concentric Maclaurin Spheroid Method
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Militzer_2019_ApJ_879_78.pdf
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Final Published Version
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Univ Arizona, Lunar & Planetary LabIssue Date
2019-07-08
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IOP PUBLISHING LTDCitation
Militzer, B., Wahl, S., & Hubbard, W. B. (2019). Models of Saturn's Interior Constructed with Accelerated Concentric Maclaurin Spheroid Method. arXiv preprint arXiv:1905.08907.Journal
ASTROPHYSICAL JOURNALRights
© 2019. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
The Cassini spacecraft's Grand Finale orbits provided a unique opportunity to probe Saturn's gravity field and interior structure. Doppler measurements yielded unexpectedly large values for the gravity harmonics J(6), J(8), and J(10), which cannot be matched using planetary interior models that assume uniform rotation. Instead we present a suite of models that assume the planet's interior rotates on cylinders, which allows us to match all the observed even gravity harmonics. For every interior model, the gravity field is calculated self-consistently with high precision using the Concentric Maclaurin Spheroid method. We present an acceleration technique for this method, which drastically reduces the computational cost, allows us to efficiently optimize model parameters and map out allowed parameter regions with Monte Carlo sampling, and increases the precision of the calculated J(2n) gravity harmonics to match the error bars of the observations, which would be difficult without acceleration. Based on our models, Saturn is predicted to have a dense central core of similar to 15-18 Earth masses and an additional 1.5-5 Earth masses of heavy elements in the envelope. Finally, we vary the rotation period in the planet's deep interior and determine the resulting oblateness, which we compare with the value from radio occultation measurements by the Voyager spacecraft. We predict a rotation period of 10:33:34 hr +/- 55 s, which is in agreement with recent estimates derived from ring seismology.ISSN
0004-637XEISSN
1538-4357Version
Final published versionSponsors
NASA missions Cassini and Juno; University of California [00013725]ae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/ab23f0