Water vapor in Titan's stratosphere from Cassini CIRS far-infrared spectra

被引：38

作者：

Cottini, V. ^{[1
]}

Nixon, C. A. ^{[1
,2
]}

Jennings, D. E. ^{[1
]}

Anderson, C. M. ^{[1
]}

Gorius, N. ^{[1
,3
]}

Bjoraker, G. L. ^{[1
]}

Coustenis, A. ^{[4
,5
]}

Teanby, N. A.

Achterberg, R. K. ^{[1
,2
]}

Bezard, B.

de Kok, R. ^{[6
]}

Lellouch, E. ^{[4
,5
]}

Irwin, P. G. J. ^{[7
]}

Flasar, F. M. ^{[1
]}

Bampasidis, G. ^{[4
,5
,8
]}

机构：

[1] NASA, GSFC, Planetary Syst Lab, Greenbelt, MD 20771 USA

[2] Univ Maryland, Dept Astron, College Pk, MD 20742 USA

[3] Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA

[4] Univ Paris Diderot, UPMC Univ Paris 06, CNRS, LESIA Observ Paris, Paris, France

[5] Univ Bristol, Sch Earth Sci, Bristol BS8 1RJ, Avon, England

[6] SRON, NL-3584 CA Utrecht, Netherlands

[7] Univ Oxford, Oxford OX1 3PU, England

[8] Univ Athens, Fac Phys, Athens 11528, Greece

来源：

ICARUS | 2012年 / 220卷 / 02期

基金：

英国科学技术设施理事会;

关键词：

Spectroscopy; Atmospheres; Composition; Satellites; Titan; ROTOTRANSLATIONAL ABSORPTION-SPECTRA; RADIATIVE-TRANSFER; CARBON-MONOXIDE; ATMOSPHERE; TEMPERATURES; PAIRS; SPECTROMETER; AEROSOLS; ENCELADUS; 50-K;

D O I：

10.1016/j.icarus.2012.06.014

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Here we report the measurement of water vapor in Titan's stratosphere using the Cassini Composite Infrared Spectrometer (CIRS, Flasar, F.M. et al. [2004]. Space Sci. Rev. 115, 169-297). CIRS senses water emissions in the far infrared spectral region near 50 mu m, which we have modeled using two independent radiative transfer codes (NEMESIS (Irwin, P.G.J. et al. [2008]. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150) and ART (Coustenis, A. et al. [2007]. Icarus 189, 35-62; Coustenis, A. et al. [2010]. Icarus 207, 461-476). 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 x 10(14) molecules/cm(2). In the latitude range 80 degrees S to 30 degrees N 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 (e.g. Lara, L.M., Lellouch, F., Lopez-Moreno, J.J., Rodrigo, R. [1996]. J. Geophys. Res. 101(23), 261; Wilson, E.H., Atreya, S.K. [2004]. J. Geophys. Res. 109, E6; Horst, S.M., Vuitton, V., Yelle, R.V. [2008]. J. Geophys. Res., 113, E10). We have also fitted our data using scaling factors of similar to 0.1-0.6 to these photochemical model profiles, indicating that the models over-predict the water abundance in Titan's lower stratosphere. (C) 2012 Elsevier Inc. All rights reserved.

引用

页码：855 / 862

页数：8

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