Venus Glory Captured for the First Time by ESA Orbiter

The European Space Agency's Venus Express orbiter captured a rainbow like feature in the atmosphere of Venus.

For the first time, a complete image of 'glory' (rainbow like feature) has been captured in the atmosphere of another planet. The 1200 km wide glory was captured 24 July 2011.

Rainbows and glories appear when sunlight falls on water droplets in the atmosphere. Rainbows form a arch across the sky whereas a glory is much smaller and consists of an array of coloured concentric rings that has a bright core. On Earth, they are most visible from airplanes flying above the clouds.   

Two key componets help in the formation of a glory - cloud particles and liquid droplets.

Venus, the brightest planet, has an atmosphere filled with droplets that are highly concentrated in sulphuric acid. This time, in order to verify the characteristics of cloud droplets, the researchers pictured the clouds along with the Sun behind the Venus Express Spacecraft.

The orbiter successfully captured the glory over Venus clouds, nearly 70 km above the surface of the planet.

Based on the observations, the researches claim that the spherical cloud particles are nearly a fiftieth of the width of a human hair (1.2 micrometres wide). Based on the width of glory (1200 km) researchers suggest that the particles present at the top most layer of the cloud are uniform. 

When compared to the water particles on Earth, these sulphuric acid cloud droplets are much smaller. The researchers were puzzled looking at the complex chemistry present in the atmosphere.

"The variations of brightness of the rings of the observed glory is different than that expected from clouds of only sulphuric acid mixed with water, suggesting that other chemistry may be at play," ESA explains on its site.

Explaining the change in brightness, the experts say it could be due to the presence of a UV absorber.  This unknown atmospheric element could be held accountable for the bizarre dark spots seen in the cloud tops of Venus at ultraviolet wavelengths.

In order to produce a definitive conclusion, the researchers suggest the need for further investigation.