New constraints on Saturn's interior from Cassini astrometric data

Lainey, V.; Jacobson, R. A.; Tajeddine, Radwan; Cooper, Nicholas J.; Murray, C. D.; Robert, Vincent; Tobie, G.; Guillot, T.; Mathis, S.; Remus, F.; Desmars, J.; Arlot, Jean-Eudes; Cuyper, Jean-Pierre De; Déhant, V.; Pascu, D.; Thuillot, W.; Poncin-Lafitte, Christophe Le; Zahn, Jean-Paul

doi:10.1016/j.icarus.2016.07.014

Cited by 168 publications

(217 citation statements)

References 44 publications

(61 reference statements)

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“…Mass and size of Saturn are shown in Table 1, which are consistent with Remus et al (2012Remus et al ( , 2015. Lainey et al (2017) assume more detailed models with layered structure and the calculation method by Tobie et al (2005), and mention that the viscosity range to generate the observed Q s is compatible between their complex model and the simple two layer model. In the structure models by Remus et al (2012Remus et al ( , 2015 and Lainey et al (2017), the fluid envelope is assumed to be non-dissipative.…”

Section: Introductionsupporting

confidence: 73%

“…As a mechanism of the observed dissipation of Saturn, Lainey et al (2017) suggest a viscoelastic response of the solid core. Although a viscoelastic core can generate significant dissipation (Remus et al 2012(Remus et al , 2015Lainey et al 2017), it contradicts the conventional estimations derived from the orbital expansion of Mimas (e.g., Goldreich & Soter 1966;Gavrilov & Zharkov 1977;Murray & Dermott 2000;Meyer & Wisdom 2007). One hypothesis is that the Saturnian satellites such as Mimas were formed recently (Charnoz et al 2011).…”

Section: Introductionmentioning

confidence: 88%

“…We calculate the past semi-major axis of Mimas taking into account the frequency dependence of the dissipation with the simple two-layer structure models by Remus et al (2012Remus et al ( , 2015. Firstly we constrain the rigidity and viscosity of the solid core, which are consistent with the latest observational results by Lainey et al (2017), and then we calculate the semi-major axis within the range of the constrained rheological parameters. Here, we consider the value of k 2s /Q s rather than Q s because k 2s /Q s is the directly obtained parameter by astrometric methods.…”

Section: Introductionmentioning

confidence: 89%

“…Lainey et al (2017) also estimated k 2s /Q s at Rhea's frequency. However, they suggest that the dissipation at Rhea's frequency is caused by turbulent friction in the envelope, which is beyond the scope of this work.…”

Section: Constraint Of Rigidity and Viscosity For Observed Dissipationmentioning

confidence: 99%

“…Lainey et al (2017) assume more detailed models with layered structure and the calculation method by Tobie et al (2005), and mention that the viscosity range to generate the observed Q s is compatible between their complex model and the simple two layer model. In the structure models by Remus et al (2012Remus et al ( , 2015 and Lainey et al (2017), the fluid envelope is assumed to be non-dissipative. Convective turbulent friction applied on fluid tidal waves (e.g., Ogilvie & Lin 2004) and the resonant-lock mechanism (Fuller et al 2016) may contribute to the dissipation in Saturn, which can compete with the viscoelastic dissipation in the solid core (Guenel et al 2014).…”

Section: Introductionmentioning

confidence: 99%

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Frequency-dependent tidal dissipation in a viscoelastic Saturnian core and expansion of Mimas’ semi-major axis

Dake¹,

Hußmann²

2017

A&A

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Context. Regarding tidal dissipation in Saturn, usually parameterized by Saturn's quality factor Q, there remains a discrepancy between conventional estimates and the latest determination that has been derived from astrometric observations of Saturn's inner satellites. If dissipation in Saturn is as large as the astrometric observations suggest, and is independent of time and tidal frequency, conventional models predict that Mimas' initial orbit should be located inside Saturn's synchronous orbit or even inside its Roche limit, in contradiction to formation models. Aims. Using simple structure models and assuming Saturn's core to be viscoelastic, we look for dissipation models which are consistent with both the latest astrometric observations and with Mimas' orbital migration. Methods. Firstly, using a two-layer model of Saturn's interior structure, we constrain the ranges of rigidity and viscosity of Saturn's core which are consistent with Saturn's dissipation derived from astrometric observations at the tidal frequencies of Enceladus, Tethys, and Dione. Next, within the constrained viscosity and rigidity ranges, we calculate Mimas' semi-major axis considering the frequency dependence of viscoelastic dissipation in Saturn's core. By the two calculations, we evaluate (1) Saturnian models which can explain the astrometrically determined Saturnian dissipation, and (2) whether Mimas' initial semi-major axis is larger than the synchronous orbit. Results. We show that if the core is assumed to be solid with a viscosity of 10 13 −10 14 Pa s (depending on its size), the lower boundary of the observed Saturnian dissipation at tidal frequencies of Enceladus, Tethys, and Dione (k 2s /Q s ∼ 4 × 10 −5 where k 2s is Saturn's second degree Love number and Q s its quality factor) can be explained by our model. In this viscosity range, Mimas can stay outside the synchronous orbit and the Roche limit for 4.5 billion years of evolution. Conclusions. In the case of a frequency dependent viscoelastic dissipative core, the lower boundary of the observed Saturnian dissipation can be consistent with the orbital expansion of Mimas. In this model, the assumption of a late formation of Mimas, discussed recently, is not required.

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Section: Introductionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 89%

Section: Constraint Of Rigidity and Viscosity For Observed Dissipationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Frequency-dependent tidal dissipation in a viscoelastic Saturnian core and expansion of Mimas’ semi-major axis

Dake¹,

Hußmann²

2017

A&A

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Enceladus's internal ocean and ice shell constrained from Cassini gravity, shape, and libration data

Čadek

Tobie

Hoolst

et al. 2016

Geophysical Research Letters

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The intense plume activity at the South Pole of Enceladus together with the recent detection of libration hints at an internal water ocean underneath the outer ice shell. However, the interpretation of gravity, shape, and libration data leads to contradicting results regarding the depth of ocean/ice interface and the total volume of the ocean. Here we develop an interior structure model consisting of a rocky core, an internal ocean, and an ice shell, which satisfies simultaneously the gravity, shape, and libration data. We show that the data can be reconciled by considering isostatic compensation including the effect of a few hundred meter thick elastic lithosphere. Our model predicts that the core radius is 180–185 km, the ocean density is at least 1030 kg/m3, and the ice shell is 18–22 km thick on average. The ice thicknesses are reduced at poles decreasing to less than 5 km in the south polar region.

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2022

Radio Science Techniques for Deep Space Exploration

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New constraints on Saturn's interior from Cassini astrometric data

Abstract: Using astrometric observations spanning more than a century and including a large set of

Cited by 168 publications

References 44 publications

Frequency-dependent tidal dissipation in a viscoelastic Saturnian core and expansion of Mimas’ semi-major axis

Frequency-dependent tidal dissipation in a viscoelastic Saturnian core and expansion of Mimas’ semi-major axis

Enceladus's internal ocean and ice shell constrained from Cassini gravity, shape, and libration data

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