Thanks to the European Space Agency‘s Venus Express orbiter, a rainbow-like feature, named a “glory”, has been recorded for the very first time elsewhere in the atmosphere of the planet closest to the Earth. Both glories and rainbows come into view when sunlight shines on particles of water or cloud droplets if one is on Earth. There are however some differences.
Glories are generally much smaller and are made up of a number of different colored concentric rings upon a bright center. Rainbows most commonly arch across a wide area of sky. Rainbows are also easy to see whereas glories can only be viewed when the viewer is positioned between the cloud particles reflecting the solar light and the sun.
On this planet, glories can be seen from aircraft surrounding the shadow of the airplane on the clouds below. To be seen, a glory requires cloud particles that are spherical—thus probably liquid droplets—that are of similar size. Scientists believe that Venus’ atmosphere is filled with droplets of sulphuric acid.
The Venus Express mission scientists had therefore recently recorded images of the clouds with the sun positioned behind the Venus Express orbiter hoping to spot a glory which would aid them in learning the specific characteristics of the cloud droplets. Their latest press release notes they were successful.
The glory images the scientists shot were visible at the top of the Venus clouds approximately 43 miles above the surface of Venus on July 24, 2011. The phenomenon was reported to be approximately 750 miles wide viewed from the Venus Express which was about 1,720 miles above the surface.
The researchers used the captured images to estimate the overall size of the cloud particles. It was determined that they are 1.2 micrometres across which is the equivalent of your average human hair. They also noticed differing degrees of brightness in the rings of the glory which they state is an effect one would not expect from clouds consisting of only water and sulphuric acid. This means that Venus’ surrounding atmosphere is more varied in composition than what was believed prior to this discovery.
(Image courtesy of ESA)