EDP Sciences
Free Access
Issue
A&A
Volume 413, Number 2, January II 2004
Page(s) L5 - L9
Section Letters
DOI https://doi.org/10.1051/0004-6361:20034637


A&A 413, L5-L9 (2004)
DOI: 10.1051/0004-6361:20034637

Letter

First detection of CO in Uranus

Th. Encrenaz1, E. Lellouch1, P. Drossart1, H. Feuchtgruber2, G. S. Orton3 and S. K. Atreya4

1  LESIA, Observatoire de Paris, 92195 Meudon, France
2  MPI, Postfach 1603, 85740 Garching, Germany
3  JPL, Pasadena, CA 91109, USA
4  The University of Michigan, Ann Arbor, MI 48109-1243, USA

(Received 30 September 2003 / Accepted 24 November 2003)

Abstract
The spectrum of Uranus has been recorded in Oct.-Nov. 2002, between 4.6 and 5.0  $\mu$m, using the ISAAC imaging spectrometer at the VLT-UT1 (ANTU) 8-m telescope of ESO. The spectral resolving power was 1500. In addition to a few strong H 3 + emission lines, the spectrum of Uranus distinctly shows the emission lines of the CO(1-0) band from R7 to P8. The relative intensity distribution of the observed CO emission is not compatible with a thermal distribution, for any value of the rotational temperature. The most likely emission mechanism is fluorescence, and a good fit is obtained assuming a constant CO mixing ratio of $3\times 10^{-8}$ at the tropopause and above. The tropospheric continuum of Uranus is also detected beween 4.7 and 5.0  $\mu$m. The observed continuum can be fitted assuming reflected sunlight above a cloud level at 3.1 bars, presumably attributed to H 2S. Upper limits of $2\times 10^{-8}$ and $1\times 10^{-6}$ are inferred for the CO and PH 3 tropospheric mixing ratios above this level. The low CO tropospheric upper limit might suggest that the CO vertical distribution is not uniform.


Key words: planets and satellites: Uranus -- infrared: solar system

Offprint request: Th. Encrenaz, Therese.Encrenaz@obspm.fr

SIMBAD Objects in preparation



© ESO 2004

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.