What's the story, Venus-Glory?

A glory is the atmospheric phenomena that produces scintillating, iridescent clouds. They're special enough to see on Earth, but now we have a photograph of a glory on Venus! I'm always down with a bit of interplanetary cloud-watching.

The physics that produces glories are fascinating. Previously, the idea was that interference patterns between different length surface waves on the water droplets resulted in the the stunning show. Newer theory is that even light that misses the droplets end up interacting with them, with classical tunnelling through the air within a droplet of water. If it resonates, it is emitted backwards, producing the rainbow effect.


Glories are usually seen paired with a magnified shadow of the observer, making you the star of your own spectacular halo. The Cloud Appreciation Society collects photographs of glories; browsing it is a lovely way to spend your coffee break.

The European Space Agency (ESA) just released a composite image of a 1,2000 kilometre diameter glory observed on Venus on 24 July 2011 by the Venus Monitoring Camera. The image combines ultraviolet, visible, and near-infrared wavelengths, photographed from 6,000 kilometres away. Because each image is taken 10 seconds apart while the spacecraft was moving, the composite layers do not overlap precisely.

Update: ESA has released more information about the composite! They were specifically trying to photograph a glory in order to better investigate clouds on Venus. From the glory, they've figured out that the droplets are probably rich in sulfuric acid, and 1.2 microns across (that's roughly 1/50th of the diameter of human hair). The enormous size of the glory means that droplets in the upper atmosphere are roughly uniform. The observed glory doesn't exactly match what was predicted by theory — it has more absorption in the ultraviolet bandwidth than makes sense for a mix of only sulfuric acid and water. Instead, some other chemical might be in the mix, absorbing instead of reflecting UV light.


Terrestrial glory with airplane shadow photographed somewhere over Canada by Brocken Inaglory. Venus glory image credit to ESA/MPS/DLR/IDA. The Bad Astronomer was also insta-infatuated with this, and has his own take on interplanetary cloud-watching.

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