Stationary waves in clouds on Venus
This sequence of images, taken with the VIRTIS instrument on Venus Express, shows stationary waves in the clouds above the night side of the planet.
Observing the thermal emission from clouds in the upper layers of Venus's atmosphere has been difficult because the contrast in infrared images was low. A team of scientists, led by Javier Peralta of the Japan Aerospace Exploration Agency (JAXA), used the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on ESA's Venus Express spacecraft to see the clouds properly for the first time, allowing them to explore what previous teams could not.
Night side upper clouds form different shapes and morphologies than those found elsewhere–large, wavy, patchy, irregular, and filament-like patterns, many of which are unseen in dayside images–and are dominated by unmoving phenomena known as stationary waves.
These waves are concentrated over steep, mountainous areas of Venus; this suggests that the planet's topography is affecting what happens up above in the clouds.
This sequence runs from 20:11:10 UTC on 27 April 2007 to 01:11:10 UTC on 28 April 2007, and was taken with the 3.9 micron filter. Careful examination shows that some of the cloud features do not move.
Another view of this sequence (in which the images are projected onto the same planar geometry) is available here.
This research is reported in 'Stationary waves and slowly moving features in the night upper clouds of Venus', by J. Peralta et al., published on 24 July 2017 in Nature Astronomy. doi: 10.1038/s41550-017-0187.