Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-23T02:35:46.569Z Has data issue: false hasContentIssue false

New clues on the interior of Titan from its rotation state

Published online by Cambridge University Press:  05 January 2015

Benoît Noyelles
Affiliation:
NAmur Center for CompleX SYStems (naXys), University of Namur, Rempart de la Vierge 8, B-5000 Namur, Belgium email: [email protected]
Francis Nimmo
Affiliation:
Department of Earth and Planetary Sciences, University of California at Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA email: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

The Saturnian satellite Titan is one of the main targets of the Cassini-Huygens mission, which revealed in particular Titan's shape, gravity field, and rotation state. The shape and gravity field suggest that Titan is not in hydrostatic equilibrium, that it has a global subsurface ocean, and that its ice shell is both rigid (at tidal periods) and of variable thickness. The rotational state of Titan consists of an expected synchronous rotation rate and an unexpectedly high obliquity (0.3○) explained by Baland et al. (2011) to be a resonant behavior. We here combine a realistic model of the ice shell and interior and a 6-degrees of freedom rotational model, in which the librations, obliquity and polar motion of the rigid core and of the shell are modelled, to constrain the structure of Titan from the observations. We consider the gravitational pull of Saturn on the 2 rigid layers, the gravitational coupling between them, and the pressure coupling at the liquid-solid interfaces.

We confirm the influence of the resonance found by Baland et al., that affects between 10 and 13% of the possible Titans. It is due to the 29.5-year periodic annual forcing. The resonant Titans can be obtained in situations in which a mass anomaly at the shell-ocean boundary (bottom loading) is from 80 to 92% compensated. This suggests a 250 to 280 km thick ocean below a 130 to 140 km thick shell, and is consistent with the degree-3 analysis of Hemingway 26 et al. (2013).

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2014 

References

Baland, R.-M., Van Hoolst, T., Yseboodt, M. & Karatekin, Ö. 2011, A&A, 530, A141Google Scholar
Baland, R.-M., Tobie, G., Lefèvre, A., & Van Hoolst, T., 2014, Icarus, 237, 29CrossRefGoogle Scholar
Bills, B. G. & Nimmo, F. 2008, Icarus, 196, 293Google Scholar
Choukroun, M. & Sotin, C. 2012, Geophysical Research Letters, 39, L04201CrossRefGoogle Scholar
Goldreich, P. M. & Mitchell, J. L. 2010, Icarus, 209, 631Google Scholar
Hemingway, D., Nimmo, F., Zebker, H., & Iess, L. 2013, Nature, 500, 550Google Scholar
Iess, L., Rappaport, N. J., & Jacobson, R. A.et al. 2010, Science, 327, 1367CrossRefGoogle Scholar
Iess, L., Jacobson, R. A., & Ducci, M.et al. 2012, Science, 337, 457Google Scholar
Lunine, J. I. & Stevenson, D. J. 1987, Icarus, 70, 61Google Scholar
Meriggiola, R. & Iess, L. 2012, European Planetary Science Congress, id. EPSC2012-593Google Scholar
Nimmo, F. & Bills, B. G. 2010, Icarus, 208, 896Google Scholar
Noyelles, B., & Nimmo, F., submittedGoogle Scholar
Richard, A., Rambaux, N., & Charnay, B. 2014, Planetary and Space Science, 93–94, 22Google Scholar
Stiles, B. W., Kirk, R. L., & Lorenz, R. D.et al. 2008, AJ, 135, 1669Google Scholar
Szeto, A. M. K. & Xu, S. 1997, Journal of Geophysical Research, 102, 27651Google Scholar
Van Hoolst, T., Baland, R.-M., & Trinh, A. 2013, Icarus, 226, 299Google Scholar
Vienne, A. & Duriez, L. 1995, A&A, 297, 588Google Scholar
Zebker, H. A., Stiles, B., & Hensley, S.et al. 2009, Science, 324, 921Google Scholar