SPECTROPHOTOMETRY OF THE JOVIAN PLANETS AND TITAN AT 300-NM TO 1000-NM WAVELENGTH - THE METHANE SPECTRUM

Full-disk albedo spectra of the jovian planets and Titan were derived from observations at the European Southern Observatory in July 1993. T he spectra extend from 300- to 1000-nm wavelength at 1-nm resolution. The signal-to-noise ratio is approximately 1000 in the visible. The ac curacy is 2% for relative and 4% for absolute albedos. Colors and magn itudes were also determined. Some 40-60 Raman scattering features are visible in the spectrum of each jovian planet. A Raman scattering mode l with five parameters adjusted for each planet can explain these feat ures. A methane absorption spectrum is given which fits methane featur es in the spectra of the jovian planets and Titan. It differs from roo m-temperature laboratory spectra but it is consistent with some limite d laboratory data at cold temperatures. Three new, weak methane bands were detected in the spectra of Uranus and Neptune. A strong absorptio n band in Jupiter's spectrum is possibly due to water, confirming a st rong depletion of oxygen in the probed part of Jupiter's atmosphere. ( C) 1994 Academic Press, Inc.