Letter to the Editor
Evidence for water vapor in Titan's atmosphere from ISO/SWS data *
A. Coustenis 1,
A. Salama 2,
E. Lellouch 1,
Th. Encrenaz 1,
G.L. Bjoraker 3,
R.E. Samuelson 3,
Th. de ,
H. Feuchtgruber 2 and
M.F. Kessler 2
Received 27 May 1998 / Accepted 2 July 1998
The infrared spectrum of Titan around 40 µm was recorded in the grating mode of the Short Wavelength Spectrometer (SWS) of ISO, with a resolving power of about 1900. Two emission features appear at 43.9 and 39.4 µm, where pure rotational water lines are expected. Line strengths are about 8 times the 1 statistical noise level. The H2O vertical profile for water suggested by the photochemical model of Lara et al. (1996), rescaled by a factor of about , is compatible with the data. The associated water mole fraction is about at an altitude of 400 km (column density of mol cm-2 above the surface). The inferred water influx at 700 km in Titan's atmosphere is in the range (0.8-2.8) mol cm-2s-1.
Key words: planets and satellites: Titan infrared: solar system
* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) with the participation of NASA and ISAS. The SWS instrument (P.I. Th. de Graauw) is a joint project of the SRON and the MPE. RES would like to thank D. Hamilton for illuminating discussions regarding dust transport in the Saturn System.
Send offprint requests to: A. Coustenis (e-mail: firstname.lastname@example.org)
This article contains no SIMBAD objects.
© European Southern Observatory (ESO) 1998
Online publication: July 27, 1998