The 2.9-4.2 micron spectrum of Saturn:: Clouds and CH4, PH3, and NH3

We have used synthetic spectra to analyze a medium resolution 2.9-4.2 mu m spectrum of Saturn's temperate region observed at UKIRT using CGS4. The synthetic spectra include CH4, PH3, and NH3 lines, for which mixing ratios were adopted from recent Cassini results. The observed absorption features in the spectrum are well accounted for by lines of these molecular species formed 22 +/- 8 kin above the I bar pressure level at similar to 610 mbar. The influence of optically thin haze particles at higher altitudes on the spectrum is not pronounced, with higher spectral resolution probably required to constrain the effects of haze in this wavelength region. Fluorescent line emission by CH4 in its 1)3 and nu(3) + nu(4) - nu(4) bands, detected in the 3.2-3.5 mu m region, originates between 400 km (similar to 0.06 mbar) and 800 kin (similar to 0.01 mu bar) above the I bar level, with peak contributions from the two major contributing bands at 550 km (similar to 3 mu bar) and 700 kin (similar to 0.1 mu bar), respectively. (c) 2005 Elsevier Inc. All rights reserved.