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Water Vapor in Titan's Stratosphere from Cassini CIRS Far-Infrared SpectraHere we report the measurement of water vapor in Titan's stratosphere using the Cassini Composite Infrared Spectrometer (CIRS). CIRS senses water emissions in the far infrared spectral region near 50 micron, which we have modeled using two independent radiative transfer codes. From the analysis of nadir spectra we have derived a mixing ratio of 0.14 +/- 0.05 ppb at an altitude of 97 km, which corresponds to an integrated (from 0 to 600 km) surface normalized column abundance of 3.7 +/- 1.3 1014 molecules/cm2. In the latitude range 80S to 30N we see no evidence for latitudinal variations in these abundances within the error bars. Using limb observations, we obtained mixing ratios of 0.13 +/- 0.04 ppb at an altitude of 115 km and 0.45 +/- 0.15 ppb at an altitude of 230 km, confirming that the water abundance has a positive vertical gradient as predicted by photochemical models. We have also fitted our data using scaling factors of 0.1-0.6 to these photochemical model profiles, indicating that the models over-predict the water abundance in Titan's lower stratosphere.
Document ID
20140010836
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1016/j.icarus.2012.06.014
Authors
Cottini, V. (Maryland Univ. College Park, MD, United States)
Nixon, C. A. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Jennings, D. E. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Anderson, C. M. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Gorius, N. (Catholic Univ. of America Washington, DC, United States)
Bjoraker, G. L. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Coustenis, A. (Observatoire de Paris France)
Teanby, N. A. (Bristol Univ. United Kingdom)
Achterberg, R. K. (Maryland Univ. College Park, MD, United States)
Bezard, B. (Bristol Univ. United Kingdom)
deKok, R, (Space Research Organization Netherlands Utrecht, Netherlands)
Lellouch, E. (Observatoire de Paris France)
Irwin, P. G. J. (Oxford Univ. Oxford, United Kingdom)
Flasar, F. M. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Bampasidis, G. (Observatoire de Paris France)
Date Acquired
August 19, 2014
Publication Date
August 1, 2012
Publication Information
Publication: Icarus
Publisher: Elsevier
Volume: 220
Issue: 2
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
GSFC-E-DAA-TN11425
Report Number: GSFC-E-DAA-TN11425
Funding Number(s)
CONTRACT_GRANT: NNG06EO90A
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
composition
titan
atmospheres
spectroscopy

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