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
收藏
页码：855 / 862
页数：8
相关论文
共 49 条
[1]   Titan's aerosol and stratospheric ice opacities between 18 and 500 μm: Vertical and spectral characteristics from Cassini CIRS [J].
Anderson, Carrie M. ;
Samuelson, Robert E. .
ICARUS, 2011, 212 (02) :762-778
[2]  
BJORAKER G, 2008, B AM ASTRON SOC, V40, P448
[3]   COLLISION-INDUCED ROTOTRANSLATIONAL ABSORPTION-SPECTRA OF N2-N2 PAIRS FOR TEMPERATURES FROM 50-K TO 300-K [J].
BORYSOW, A ;
FROMMHOLD, L .
ASTROPHYSICAL JOURNAL, 1986, 311 (02) :1043-1057
[4]   MODELING OF COLLISION-INDUCED INFRARED-ABSORPTION SPECTRA OF H2-H2 PAIRS IN THE FUNDAMENTAL-BAND AT TEMPERATURES FROM 20-K TO 300-K [J].
BORYSOW, A .
ICARUS, 1991, 92 (02) :273-279
[5]   COLLISION-INDUCED ROTOTRANSLATIONAL ABSORPTION-SPECTRA OF CH4-CH4 PAIRS AT TEMPERATURES FROM 50-K TO 300-K [J].
BORYSOW, A ;
FROMMHOLD, L .
ASTROPHYSICAL JOURNAL, 1987, 318 (02) :940-943
[6]   THEORETICAL COLLISION-INDUCED ROTOTRANSLATIONAL ABSORPTION-SPECTRA FOR MODELING TITANS ATMOSPHERE - H2-N2 PAIRS [J].
BORYSOW, A ;
FROMMHOLD, L .
ASTROPHYSICAL JOURNAL, 1986, 303 (01) :495-510
[7]   THEORETICAL COLLISION-INDUCED ROTOTRANSLATIONAL ABSORPTION-SPECTRA FOR THE OUTER PLANETS - H2-CH4 PAIRS [J].
BORYSOW, A ;
FROMMHOLD, L .
ASTROPHYSICAL JOURNAL, 1986, 304 (02) :849-865
[8]   FAR-INFRARED CIA SPECTRA OF N2-CH4 PAIRS FOR MODELING OF TITANS ATMOSPHERE [J].
BORYSOW, A ;
TANG, CM .
ICARUS, 1993, 105 (01) :175-183
[9]   Collisional spreading of Enceladus' neutral cloud [J].
Cassidy, T. A. ;
Johnson, R. E. .
ICARUS, 2010, 209 (02) :696-703
[10]   Spatial and temporal variations in Titan's surface temperatures from Cassini CIRS observations [J].
Cottini, V. ;
Nixon, C. A. ;
Jennings, D. E. ;
de Kok, R. ;
Teanby, N. A. ;
Irwin, P. G. J. ;
Flasar, F. M. .
PLANETARY AND SPACE SCIENCE, 2012, 60 (01) :62-71
12345