62th ohio state university symposium on molecular spectroscopy june 18–22, 2007 recent...
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62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
RECENT APPLICATIONS AND FUTURE PROSPECTS OF METHANE
SPECTROSCOPY TO THE ATMOSPHERE OF TITAN
RECENT APPLICATIONS AND FUTURE PROSPECTS OF METHANE
SPECTROSCOPY TO THE ATMOSPHERE OF TITAN
Vincent BOUDONInstitut Carnot de Bourgogne – UMR 5209 CNRS-Université de Bourgogne, 9 Av. A. Savary, BP 47870, F-21078 DIJON, France
Athéna COUSTENIS, Emmanuel LELLOUCH, Pierre DROSSARTLESIA, Observatoire de Paris-Meudon, 5 Place Jules Jansen, F-92195 MEUDON, France
Alberto NEGRÃOObservatorio Astronomico and Faculdade de Ciências da Universidade de Lisboa, 1749-016, LISBOA, Portugal
Caitlin A. GRIFFITHLunar and Planetary Laboratory, University of Arizona, TUCSON, AZ 85721, USA
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
ContentsContents
I. Methane on Titan
II. Status of CH4 spectroscopy
III. Application of the octad’s modeling
IV. Perspectives for CH4 spectroscopy
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
I. Methane on TitanI. Methane on Titan
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Titan: Methane everywhere!Titan: Methane everywhere!
Lakes
Rivers Cryovolcanoes?
Clouds
Atmosphere
Soil (clathrates?)
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
DISR spectrum of Titan (Huygens / ESA)DISR spectrum of Titan (Huygens / ESA)2.0
1.5
1.0
0.5
0.01.61.41.21.00.8
/ Wavelengthμm
12000 10000 9000 8000 7000 6000 / Wavenumber cm-1
= , = 30 Target Sun Altitude km
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Use of CH4 spectroscopy on TitanUse of CH4 spectroscopy on Titan• Measure methane concentration (1.6 % stratosphere, 5 % ground)
• Determine methane’s origin
• Retrieve methane vertical profiles
• Remove methane spectrum to find minor species
• Retrieve haze profile
• Measure surface albedo
Visible 939 nm
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
II. Status of CH4 spectroscopyII. Status of CH4 spectroscopy
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
The polyads of CH4The polyads of CH4
« Saturn Methane Image » – 16/02/2004
Cassini / MT2 Filter : 727 nm = 13755 cm-1
Global fit
Titan
939 nm CH4 window
1.5
1.0
0.5
0.0
1200
011
000
1000
090
0080
0070
0060
00 /
Wavenumber
cm-1
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Present status of CH4 analyses (early 2007)Present status of CH4 analyses (early 2007)
Polyad / Spectral region Line positions Line intensities Line shapes
1 – Ground state
0–200 cm-1 (> 5.0 μm)
Complete analysis,
J ≤ 24Complete analysis No analysis
2 – Dyad
1000–1800 cm-1 (5.6–10.0 μm)
Complete analysis,
J ≤ 23Complete analysis,
with some hot bands
Perturbers:
He et N2
3 – Pentad
2200–3300 cm-1 (3.0–4.6 μm)
Complete analysis,
J ≤ 18Complete analysis,
cold bands only
Perturbers:
He, Ar, N2, O2, CH4
4 – Octad
3700–4800 cm-1 (2.0–2.7 μm)
Complete analysis,
J ≤ 16Complete analysis,
cold bands onlyNo analysis
5 – Tetradecad
5400–6300 cm-1 (1.6–1.9 μm)
Incomplete analysis,
J ≤ 10Partial analysis, cold
bands onlyNo analysis
6 – Icosad
6600–7700 cm-1 (1.3 – 1.5 μm)Very partial analysis of 1 band among 20
No analysis No analysis
Upper polyads
> 7800 cm-1 (< 1.28 μm)No analysis No analysis No analysis
Windows
(polyad far wings, all regions)No analysis No analysis No analysis
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
III. Application of the octad’s modelingIII. Application of the octad’s modeling
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
3 μm region with ISO spectra 3 μm region with ISO spectra12CH4 + 13CH4 + 12CH3D absorption coefficients calculated thanks to Dijon analyses
Modeling of ISO (and Keck II) data, including haze profile
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Surface albedo from CFHT/FTS spectraSurface albedo from CFHT/FTS spectra
2
2 μm window
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
VLT/NACO spectrum of Huygens site (I)VLT/NACO spectrum of Huygens site (I)
A. Negrão, M. Hirtzig, A. Coustenis,E. Gendron, P. Drossart, P. Rannou,M. Combes and V. Boudon,J. Geophys. Res. Planets 112, E02S92 (2007)
VLT (NAOS/CONICA image)January 16, 2005
Huygens landing site
Bright region
Darkregion
NB: Measurement error(3) above 2.12 μm is ± 27 %
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
VLT/NACO spectrum of Huygens site (II)VLT/NACO spectrum of Huygens site (II)
A. Negrão, M. Hirtzig, A. Coustenis, E. Gendron, P. Drossart, P. Rannou, M. Combes and V. Boudon,J. Geophys. Res. Planets 112, E02S92 (2007)
(Irwin = « band » model)
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Discovery of a polar ethane cloudDiscovery of a polar ethane cloud
C. A. Griffith, P. Penteado, P. Rannou,R. Brown, V. Boudon, K. H. Baines,R. Clark, P. Drossart, B. Buratti,P. Nicholson, C. P. McKay, A. Coustenis, A. Negrão and R. Jaumann,Science 313, 1620–1622 (2006)
Octad
2.11 μm
2.17 μm
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
IV. Perspectives for CH4 spectroscopyIV. Perspectives for CH4 spectroscopy
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Spectroscopy of CH4: what next?Spectroscopy of CH4: what next?
•Continue the global analysis approach
•Next goal: the Tetradecad (5400 – 6300 cm-1)
•Add new data (positions & intensities, hot bands)
•Windows (high J, far wings)
New approches :New approches :
•Use of the ab initio potential energy surface to calculate the effective Hamiltionian and dipole moment (cf. work of Vl. G. Tyuterev, Reims, France)
•Statistical approach for hot bands
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
The triacontadThe triacontadSpectre : L. R. Brown (JPL/KPNO)
1.5
1.0
0.5
0.0920090008800860084008200
/ Wavenumber cm-1
DISR
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
The STDS database
The STDS database
Spherical Top Data System
www.u-bourgogne.fr/LPUB/shTDS.html
• Molecular parameter database
• Calculation and analysis programs
• XTDS : Java interface
62th Ohio State University Symposium on Molecular Spectroscopy • June 18–22, 2007
Post-doctoral postition available in Dijon!Post-doctoral postition available in Dijon!
Modelling of methane absorption in the near infrared region and application to planetary atmospheres
12 months position
Contact:
NEW !