Theory of the rotation of Janus and Epimetheus

Noyelles, Benoît

doi:10.1016/j.icarus.2009.12.034

Cited by 16 publications

(14 citation statements)

References 56 publications

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“…Features at the surface of Europa have been interpreted as an evidence for supersynchronous rotation (Geissler et al 1998), the present study cannot explain it, but an influence of the interior is not to be discarded. (Vienne & Duriez 1995), and the mean motions of Janus and Epimetheus, taken from (Noyelles 2010). The masses come from (Jacobson et al 2006(Jacobson et al , 2008, and the Stokes coefficients from (Iess et al 2014;Tortora et al 2016;Iess et al 2010 Richard et al (2014) This study…”

Section: Resultsmentioning

confidence: 96%

Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

Noyelles

2017

Icarus

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Most of the main planetary satellites of our Solar System are expected to be in synchronous rotation, the departures from the strict synchronicity being a signature of the interior. Librations have been measured for the Moon, Phobos, and some satellites of Saturn. I here revisit the theory of the longitudinal librations in considering that part of the interior is not hydrostatic, i.e. has not been shaped by the rotational and tidal deformations, but is fossil. This consideration affects the rotational behavior.For that, I derive the tensor of inertia of the satellite in splitting these two parts, before proposing an analytical solution that I validate with numerical simulations. I apply this new theory on Mimas and Epimetheus, for which librations have been measured from Cassini data. I show that the large measured libration amplitude of these bodies can be explained by an excess of triaxiality that would not result from the hydrostatic theory. This theory cannot explain the phase shift which has been measured in the diurnal librations of Mimas. This speaks against a solid structure for Mimas, i.e. Mimas could have a global internal ocean.

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Section: Resultsmentioning

confidence: 96%

Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

Noyelles

2017

Icarus

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“…2 demonstrates that the effect of elasticity is four orders of magnitude smaller, since the difference between the trajectories of an elastic and of a rigid moon, computed from Eqs. (22) and (25), respectively, is at most 0.0002 meters.…”

Section: Resultsmentioning

confidence: 99%

The obliquity of Enceladus

Baland

Yseboodt

Hoolst

2016

Icarus

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“…As a result, the rotation axis of Io's mantle precesses as a rigid body with a polar moment of inertia equal to C m but with a moment of inertia difference (C − A) equal to the one of the entire body. Solution (22) can also be written as…”

Section: Iomentioning

confidence: 99%

“…(1). The interested reader is invited to consult Appendix B of Noyelles (2010) who also find that the torque is proportional to (C − A). We note that equation (44) is consistent with the small angle approximation which can be obtained from Eq.…”

Section: A Angular Momentum Equationmentioning

confidence: 99%

Obliquity of the Galilean satellites: The influence of a global internal liquid layer

Baland¹,

Yseboodt²,

Hoolst³

2012

Icarus

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The obliquity of the Galilean satellites is small but not yet observed. Studies of cycloidal lineaments and strike-slip fault patterns on Europa suggest that Europa's obliquity is about 1 deg, although theoretical models of the obliquity predict the obliquity to be one order of magnitude smaller for an entirely solid Europa. Here, we investigate the influence of a global liquid layer on the obliquity of the Galilean satellites. Io most likely has a fully liquid core, while Europa, Ganymede, and Callisto are thought to have an internal global liquid water ocean beneath an external ice shell. We use a model for the obliquity based on a Cassini state model extended to the presence of an internal liquid layer and the internal gravitational and pressure torques induced by the presence of this layer. We find that the obliquity of Io only weakly depends on the different internal structure models considered, because of the weak influence of the liquid core which is therefore almost impossible to detect through observations of the obliquity. The obliquity of Europa is almost constant in time and its mean value is smaller (0.033 − 0.044 deg) with an ocean than without (0.055 deg). An accuracy of 0.004 deg (about 100 m on the spin pole location at the surface) would allow detecting the internal ocean. The obliquity of Ganymede and Callisto depends more on their interior structure because of the possibility of resonant amplifications for some periodic terms of the solution. Their ocean may be easily detected if, at the measuring time, the actual internal structure model lead to a very different value of the obliquity than in the solid case. A long-term monitoring of their shell obliquity would be more helpful to infer information on the shell thickness.

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Theory of the rotation of Janus and Epimetheus

Cited by 16 publications

References 56 publications

Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

Interpreting the librations of a synchronous satellite – How their phase assesses Mimas’ global ocean

The obliquity of Enceladus

Obliquity of the Galilean satellites: The influence of a global internal liquid layer

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