Shapes of the saturnian icy satellites and their significance

P. C. Thomas; J. A. Burns; P. Helfenstein; S. Squyres; J. Veverka; C. Porco; E. P. Turtle; A. McEwen; T. Denk; B. Giese; T. Roatsch; T. V. Johnson; R. A. Jacobson

doi:10.1016/j.icarus.2007.03.012

Shapes of the saturnian icy satellites and their significance

P. C. Thomas, J. A. Burns, P. Helfenstein, S. Squyres, J. Veverka, C. Porco, E. P. Turtle, A. McEwen, T. Denk, B. Giese, T. Roatsch, T. V. Johnson, R. A. Jacobson

Research output: Contribution to journal › Article › peer-review

131 Scopus citations

Abstract

The sizes and shapes of six icy saturnian satellites have been measured from Cassini Imaging Science Subsystem (ISS) data, employing limb coordinates and stereogrammetric control points. Mimas, Enceladus, Tethys, Dione and Rhea are well described by triaxial ellipsoids; Iapetus is best represented by an oblate spheroid. All satellites appear to have approached relaxed, equilibrium shapes at some point in their evolution, but all support at least 300 m of global-wavelength topography. The shape of Enceladus is most consistent with a homogeneous interior. If Enceladus is differentiated, its shape and apparent relaxation require either lateral inhomogeneities in an icy mantle and/or an irregularly shaped core. Iapetus supports a fossil bulge of over 30 km, and provides a benchmark for impact modification of shapes after global relaxation. Satellites such as Mimas that have smoother limbs than Iapetus, and are expected to have higher impact rates, must have relaxed after the shape of Iapetus was frozen.

Original language	English (US)
Pages (from-to)	573-584
Number of pages	12
Journal	Icarus
Volume	190
Issue number	2
DOIs	https://doi.org/10.1016/j.icarus.2007.03.012
State	Published - Oct 2007

Keywords

Interiors
satellites
Satellites
Saturn
shapes

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

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10.1016/j.icarus.2007.03.012

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title = "Shapes of the saturnian icy satellites and their significance",

abstract = "The sizes and shapes of six icy saturnian satellites have been measured from Cassini Imaging Science Subsystem (ISS) data, employing limb coordinates and stereogrammetric control points. Mimas, Enceladus, Tethys, Dione and Rhea are well described by triaxial ellipsoids; Iapetus is best represented by an oblate spheroid. All satellites appear to have approached relaxed, equilibrium shapes at some point in their evolution, but all support at least 300 m of global-wavelength topography. The shape of Enceladus is most consistent with a homogeneous interior. If Enceladus is differentiated, its shape and apparent relaxation require either lateral inhomogeneities in an icy mantle and/or an irregularly shaped core. Iapetus supports a fossil bulge of over 30 km, and provides a benchmark for impact modification of shapes after global relaxation. Satellites such as Mimas that have smoother limbs than Iapetus, and are expected to have higher impact rates, must have relaxed after the shape of Iapetus was frozen.",

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author = "Thomas, {P. C.} and Burns, {J. A.} and P. Helfenstein and S. Squyres and J. Veverka and C. Porco and Turtle, {E. P.} and A. McEwen and T. Denk and B. Giese and T. Roatsch and Johnson, {T. V.} and Jacobson, {R. A.}",

note = "Funding Information: This work was supported in part by NASA's Cassini project. A portion of this work was done at the Jet Propulsion Laboratory, California Institute of Technology under a grant from NASA. We thank Brian Carcich, Karla Consroe, P. Fraser Helfenstein, Pamela Smith, Amy Shaw, and Tom McCarthy for technical assistance. Reviews by David Obrien and an anonymous reviewer were most useful.",

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AU - Thomas, P. C.

AU - Burns, J. A.

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AU - Squyres, S.

AU - Veverka, J.

AU - Porco, C.

AU - Turtle, E. P.

AU - McEwen, A.

AU - Denk, T.

AU - Giese, B.

AU - Roatsch, T.

AU - Johnson, T. V.

AU - Jacobson, R. A.

N1 - Funding Information: This work was supported in part by NASA's Cassini project. A portion of this work was done at the Jet Propulsion Laboratory, California Institute of Technology under a grant from NASA. We thank Brian Carcich, Karla Consroe, P. Fraser Helfenstein, Pamela Smith, Amy Shaw, and Tom McCarthy for technical assistance. Reviews by David Obrien and an anonymous reviewer were most useful.

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N2 - The sizes and shapes of six icy saturnian satellites have been measured from Cassini Imaging Science Subsystem (ISS) data, employing limb coordinates and stereogrammetric control points. Mimas, Enceladus, Tethys, Dione and Rhea are well described by triaxial ellipsoids; Iapetus is best represented by an oblate spheroid. All satellites appear to have approached relaxed, equilibrium shapes at some point in their evolution, but all support at least 300 m of global-wavelength topography. The shape of Enceladus is most consistent with a homogeneous interior. If Enceladus is differentiated, its shape and apparent relaxation require either lateral inhomogeneities in an icy mantle and/or an irregularly shaped core. Iapetus supports a fossil bulge of over 30 km, and provides a benchmark for impact modification of shapes after global relaxation. Satellites such as Mimas that have smoother limbs than Iapetus, and are expected to have higher impact rates, must have relaxed after the shape of Iapetus was frozen.

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Shapes of the saturnian icy satellites and their significance

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ASJC Scopus subject areas

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