Spectroscopy of the Cameron bands in the Mars airglow

Mars airglow spectra obtained by the ultraviolet spectrometer on board the Mariner 9 spacecraft were analyzed by using a high-resolution synthesis of the observed emissions. Bright limb observations were made of altitudes between 88 and 180 km of which the brightest features are the carbon monoxide Cameron bands in the wavelength region 1800-2600 A. The shape of these bands cannot be characterized by a single rotational temperature, but is best described by temperatures of 1600 K for lower J values and 10,000 K for higher J values. The observed zenith intensity of 16.7 kR is in good agreement with an excitation theory in which electron-impact dissociation is the most important mechanism. The observations suggest the value of the cross section for this process should be 7 x 10 to the -17th/sq cm. The first negative bands of CO(+) are not identified in the Mariner 9 spectra. This is consistent with the excitation theory for these bands.