EDP Sciences
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Volume 441, Number 1, October I 2005
Page(s) 379 - 389
Section Planets and planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20053100

A&A 441, 379-389 (2005)
DOI: 10.1051/0004-6361:20053100

Imaging Saturn's rings with CAMIRAS: thermal inertia of B and C rings

C. Ferrari1, P. Galdemard1, P. O. Lagage1, E. Pantin1 and C. Quoirin2

1  Laboratoire AIM, Unité Mixte de Recherche No. 7158 CEA-CNRS-Université Paris 7, France
    e-mail: cferrari@cea.fr,galdemard@cea.fr,lagage@cea.fr,epantin@cea.fr
2  Université Paris 6 - Pierre et Marie Curie, France

(Received 21 March 2005 / Accepted 11 May 2005)

Thermal inertias $\Gamma$ of Saturn's B and C ring particles have been derived from infrared observations using the CAMIRAS camera mounted on the Canada-France-Hawaii Telescope. They are respectively $\Gamma_{\rm B}=5^{+18}_{-2}$  ${\rm J \,m^{-2}\, K^{-1} \,s^{-1/2}}$ and $\Gamma_{\rm C}=6^{+12}_{-4}$ ${\rm J \,m^{-2}\, K^{-1} \,s^{-1/2}}$. Such low values might be characteristic of a frosty and porous regolith fractured by cracks or of very porous particle aggregates. Particles have to be slowly spinning to explain the observed ring temperatures. A large azimuthal asymmetry with an amplitude about 1 K is detected on the West ansa of the B ring. It cannot be explained by a model that considers the ring as a slab of low thermal inertia rapidly warming up to the sunlight after its eclipse into the planetary shadow.

Key words: planetary rings -- infrared: solar system -- conduction -- radiation mechanism: thermal

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