New indication for a dichotomy in the interior structure of Uranus and Neptune from the application of modified shape and rotation data

By N. Nettelmann, R. Helled, Jon Fortney, Ronald Redmer. 2012

191 citations recorded by the source corpus.

Abstract Since the Voyager fly-bys of Uranus and Neptune, improved gravity field data have been derived from long-term observations of the planets' satellite motions, and modified shape and solid-body rotation periods were suggested. A faster rotation period (−40 min) for Uranus and a slower rotation period (+1h20) of Neptune compared to the Voyager data were found to minimize the dynamical heights and wind speeds. We apply the improved gravity data, the modified shape and rotation data, and the physical LM-R equation of state to compute adiabatic three-layer structure models, where rocks are confined to the core, and homogeneous thermal evolution models of Uranus and Neptune. We present the full range of structure models for both the Voyager and the modified shape and rotation data. In contrast to previous studies based solely on the Voyager data or on empirical EOS, we find that Uranus and Neptune may differ to an observationally significant level in their atmospheric heavy element mass fraction Z1 and nondimensional moment of inertia, λ . For Uranus, we find Z 1 ≤ 8 % and λ = 0.2224 ( 1 ) , while for Neptune Z 1 ≤ 65 % and λ = 0.2555 ( 2 ) when applying the modified shape and rotation data, while for the unmodified data we compute Z 1 ≤ 17 % and λ = 0.230 ( 1 ) for Uranus and Z 1 ≤ 54 % and λ = 0.2410 ( 8 ) for Neptune. In each of these cases, solar metallicity models ( Z 1 = 0.015 ) are still possible. The cooling times obtained for each planet are similar to recent calculations with the Voyager rotation periods: Neptune's luminosity can be explained by assuming an adiabatic interior while Uranus cools far too slowly. More accurate determinations of these planets' gravity fields, shapes, rotation periods, atmospheric heavy element abundances, and intrinsic luminosities are essential for improving our understanding of the internal structure and evolution of icy planets.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/5a9b7b22fc293a4f18b66ec4f07ce185511e7de4

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In Astronomy and Astrophysics

1. Jon Fortney
2. C. Mordasini
3. Th. Henning
4. N. Madhusudhan
5. Björn Benneke
6. R. van Boekel
7. T. Greene
8. K. Zahnle

In Molecular Biology

1. Jon Fortney
2. C. Mordasini
3. Th. Henning
4. N. Nettelmann

Citations in the corpus

• A FRAMEWORK FOR CHARACTERIZING THE ATMOSPHERES OF LOW-MASS LOW-DENSITY TRANSITING PLANETS (2013, methodology): “Recently, Nettelmann et al. (2013) have investigated constraints on the interior structure, including uncertainties in the gravity fields, shapes, and rotation rates of the planets.”
• THE IMPRINT OF EXOPLANET FORMATION HISTORY ON OBSERVABLE PRESENT-DAY SPECTRA OF HOT JUPITERS (2016, methodology): “(4) the ZPl/Z found from the heavy element masses MZ in the interiors of the Solar System giant planets estimated from internal structure models for Jupiter and Saturn by Saumon & Guillot (2004) for different EOS and for Uranus and Neptune by Helled et al. (2011); Nettelmann et al. (2013).”