Cause of terrestrial nightglow continuum

Since the nightglow’s green continuum was discovered over 40 years ago the theory that it arises from the NO2 air afterglow has been generally accepted so that its intensity is regarded as a useful measure of the abundance of nitric oxide in the lower thermosphere. This theory is shown to be untenable. Observational evidence points unambiguously to a novel source: metastable oxygen molecules colliding with ambient gas molecules and thereby forming complexes that dissociate by allowed radiative transitions.