Infrared reflectivity of frost and the Venus clouds

Laboratory reflection spectra have been obtained for very small frost particles (less than 2 μ in diameter) in the spectral range from 0.9 to 3.4 μ. These spectra differ from the spectra of large ice particles, particularly in the near-absence of reflectivity minima near 1.5 and 2.0 μ. Clouds of these particles would exhibit a reflection spectrum in close agreement with that of the Venus clouds, despite any question of gaseous CO2 absorption in the Venus atmosphere. Ice remains the best candidate for the principal constituent of Venus clouds.