Rainbow-like "glory" spotted in Venus cloud particles

Simulated views of the glory phenomena on Venus (left) and Earth (right), without considering any effects of haze or background cloud brightness.
ESA/C. Wilson/P. Laven

For the first time ever, a rainbow-like feature has been spotted on another planet. Spotted in the clouds surrounding Venus, the sighting offers important clues into understanding the planet's atmosphere.

The European Space Agency's Venus Express orbiter captured images of the glory -- similar to a rainbow, but circular in shape -- on July 24, 2011. It is about 746 miles wide.

If you've ever spotted a rainbow-like circle surrounding the shadow of an airplane while flying above the clouds, you've seen a glory. They form when sunlight reflects off of cloud particles, and they're only visible when the viewer is directly between the Sun and the particles.

The ESA was hoping to spot a glory in order to confirm long-held theories about the atmosphere of Earth's closest planetary neighbor.

What they saw in the images confirmed that there is still much to learn about Venus. The color variation in the rings reveals that the cloud particles are more chemically complex than previously thought -- if they were primarily comprised of sulfuric acid and water, as expected, there would be less variation.

Two aerospace firms recently announced additional plans to study the atmosphere of Venus. Northrop Grumman and L'Garde are working on an unmanned, inflatable aircraft that would study the planet for up to a year.