Tracking clouds in the Venusian night

These infrared images were taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express on 25 April 2006, while the spacecraft was flying over low planetary latitudes (between 15º and 60º south).

The two images on the left panel (taken at 2.3 and 1.7 microns, respectively) show a fine atmospheric structure below the Venusian cloud deck, at about 35 and 20 kilometres altitude, respectively.

The right panel is the result of the projection on geographical coordinates of the second image of the left panel. The images at the top where taken from a distance of about 6000 kilometres from the surface, allowing VIRTIS to generate the high resolution details visible at the top of the panel. While Venus Express continued flying over the planet it got farer from the surface – up to 20 000 kilometres distance – allowing VIRTIS to obtain a wider view, but in lower resolution.

Stripe-like features are visible at the bottom of all images. They could be indicative of a wave-like atmospheric motion (due to tidal forces?), but their nature is still unexplained.
The separate images can be downloaded here:
[Cloud_tracking_infrared_b_H.tif,
Cloud_tracking_infrared_c_H.tif,
Wind_tracking_b_H.tif]