Differential infrared lunar emission spectroscopy

Differential 8- to 13-μ spectroscopy of 22 lunar points, spanning the major types of lunar features, was undertaken at a spatial resolution of 20–40 seconds of arc to determine if compositional or age differences are evidenced in the emission spectra. A method was devised to remove precisely the atmospheric absorption and to allow the integration of many spectra in order to reduce uncertainties caused by atmospheric absorption fluctuations and detector noise. Twenty of the 22 points showed no spectral differences greater than 0.5–1.0%. Two points, Plato and Mare Humorum, showed definite, consistent spectral differences from the other points measured, at the short wavelength end of the spectrum. An interpretation of these differences is made by using the laboratory emission spectra of silicates and other materials.