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Science Case 2.2 - Methane Spectroscopy: Problem Description

The near-infrared spectrum of Titan, as well as the one of all giant planets, is dominated by strong methane absorption bands. A precise modeling of the atmospheric methane is required in order to analyze the Titan spectra taken by CASSINI/VIMS and Huygens/DISR. It is not easy to obtain because:

  • It involves very complex high-energy vibrational polyads.
  • The study of transparence windows implies rotationally highly excited levels as well as contributions from the far wings of intense lines.
  • A study of the minor isotopologues is needed.

To solve this problem, it is necessary to couple together several approaches:

  • Line-by-line analyses.
  • New measurements at low temperature and very long optical paths, in order to better simulate Titan's conditions.
  • High-quality quantum chemistry calculations combined with new theoretical tools to convert the results into synthetic spectra.
  • Theory of lineshapes for methane perturbed by N2 or H2.

Available files
File subject File format
Methane Titan (November 2007) .pdf
Methane Spectroscopy (2008) .ppt

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