It shows numerous high-contrast features, caused by an unknown chemical in the clouds that absorbs ultraviolet light, creating the bright and dark zones.

With data from Venus Express, scientists have learnt that the equatorial areas on Venus that appear dark in ultraviolet light are regions of relatively high temperature, where intense convection brings up dark material from below. In contrast, the bright regions at mid-latitudes are areas where the temperature in the atmosphere decreases with depth. The temperature reaches a minimum at the cloud tops suppressing vertical mixing. This annulus of cold air, nicknamed the ‘cold collar’, appears as a bright band in the ultraviolet images.

Credits: ESA/MPS/DLR/IDA

The lower left shows a differential temperature map (not absolute values) of the venusian cloud tops, derived from the Visible and Infrared Thermal Imaging Spectrometer, VIRTIS, on the planet’s night-side. The darker the region, the colder the cloud tops. To the upper right is an ultraviolet image of the venusian day side, captured by the Venus Monitoring Camera, VMC, simultaneously with the night-side infrared image.

The ultraviolet reveals the structure of the clouds and the dynamical conditions in the atmosphere, whereas the infrared provides information on the temperature and altitude of the cloud tops.

Credits: VMC ultraviolet image: ESA/MPS/DLR/IDA
VIRTIS infrared image: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA