Mars: The Origin of the 3.58- and 3.69-Micron Minima in the Infrared Spectra

Abstract

The 3- to 4-micron spectra of Mars, recorded with the 200-inch telescope in 1958, were reexamined in order to ascertain whether the minima at 3.58 and 3.69 microns are due to telluric HDO molecules. Solar spectra obtained at Denver and water vapor abundances derived from radiosonde flights during the observing period were used. There seems to be a correlation between the intensities of the 3.58- and 3.69-micron features and the amount of telluric water vapor in the optical path. An important corollary is that there is no evidence for attributing these spectral features to Mars.