EDP Sciences
Free access
Issue A&A
Volume 466, Number 1, April IV 2007
Page(s) 395 - 398
Section Planets and planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:20067021

A&A 466, 395-398 (2007)
DOI: 10.1051/0004-6361:20067021

Ices on (90377) Sedna: confirmation and compositional constraints

J. P. Emery1, 2, C. M. Dalle Ore1, 2, D. P. Cruikshank1, Y. R. Fernández3, D. E. Trilling4, and J. A. Stansberry4

1  NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035, USA
    e-mail: [jemery;cdalleore]@mail.arc.nasa.gov, Dale.P.Cruikshank@nasa.gov
2  Carl Sagan Center, SETI Institute, 515 N Whisman Rd, Mountain View, CA 94043, USA
3  University of Central Florida, Department of Physics, 4000 Central Florida Blvd, M.A.P. Bulding, Orlando, FL 32816-2385, USA
    e-mail: yfernandez@physics.ucf.edu
4  University of Arizona, Steward Observatory, 933 N Cherry Ave., Tucson, AZ 85721, USA
    e-mail: [trilling; stansber]@as.arizona.edu

(Received 23 December 2006 / Accepted 25 January 2007)

We report measurements of reflectances of 90377 Sedna at $\lambda > 2.5$ $\mu$m using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. Sedna orbits well beyond even the Kuiper Belt, with a perihelion distance of 76 AU, and is therefore very faint as viewed from Earth, despite its relatively large size. Previously published near-infrared spectra show possible signatures of CH4 and N2 at ~2.3 and ~2.15 $\mu$m, respectively. These and other ices also exhibit much stronger absorptions at $\lambda > 2.5~\mu$m, providing the motivation for the present work. We detected flux from Sedna at 3.6 and 4.5 $\mu$m, but not at 5.8 or 8.0 $\mu$m. The measured IRAC fluxes are converted to geometric albedos and combined with previous measurements of the visible and near-infrared spectra. Strong absorption at both 3.6 and 4.5 $\mu$m (relative to the 2.0-2.5 $\mu$m region) is readily apparent, confirming the presence of ices on the surface of Sedna. Spectral modeling of the full wavelength range (0.4-4.5 $\mu$m) provides further constraints. We find that CH4 is required to fit the new data points, but that these new data points can not be adequately described with models containing CH4 and N2 as the only ices. We suggest that H2O ice is also present. Several characteristics of the spectrum of Sedna suggest an absence of atmospheric volatile transport, in contrast to the large objects Eris and 2005 FY9.

Key words: planets and satellites: individual: Sedna -- Kuiper Belt -- solar system: general -- infrared: solar system

© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)