Scattered UV solar radiation within the clouds of Venus

The spectral albedo curve of Venus shows a steep decline at wavelengths between 0.5 and 0.3 µm (refs 1–3). This is of interest since absorption of solar energy in this spectral region has a strong influence on the thermal balance of the venusian atmosphere. The nature and altitude distribution of the UV absorber have not been determined, although some candidate gases have been proposed. We report here the results of measurements carried out on the last Soviet venusian descent probe Venera-14 which suggest that the UV absorption is by aerosols above an altitude of 57 km and by gases below this level.