On the Identification of the 642o a Absorption Feature in the Spectra of Uranus and Neptune

We have found a methane band at A6420 that appears to account satisfactorily for an absorption observed at this wavelength in spectra of Uranus and Neptune. There thus appears to be no compelling reason to continue to attribute this feature to pressure-induced absorption by hydrogen. Inability to reproduce weak planetary methane absorptions with a 10 km amagat path in the laboratory suggests that the methane abundances in the atmospheres of both planets may be grossly underestimated. Subject headings: line identifications - Neptune - spectra, planetary - Uranus