The First Rainbow Seen on Another Planet
In a colourful first, astronomers have captured the image of a rare type of rainbow, or ’glory’, on another planet.Rainbows appear on Earth due to light refracting off water droplets. In the case of this rainbow on Venus, light is refracting off a previously observed haze that is thought to be sulfuric acid!
Wojciech Markiewicz of the Max Planck Institute for Solar System Research in Gottingen, Germanytold New Scientist, "A full glory has never been seen before outside of the terrestrial environment."
From NewScientist.com:
Scientists think glories occur when sunlight bounces about inside the droplets and ends up leaving in the same direction it came from, making a ring of light that can only be seen if you’re precisely between the sun and the centre of the glory. The particles must also be nearly spherical and almost all the same size.
Ever since the first spectra of Venus was taken in the 1920s, scientists have known that the hazy planet’s atmosphere contains sulphuric acid "clouds", which could create glories. But there was another, unidentified component in the atmosphere that absorbed light in the ultraviolet range. Scientists have come up with a variety of possible culprits, but none has been confirmed. "Even such bizarre things as bacteria were proposed, but no one really knows what it is," says Markiewicz.
In 2011, he and his colleagues manoeuvred the European Space Agency’s Venus Express spacecraft into position to hunt for Venusian glories, and on 24 July they were successful, as they reported last month in the journal Icarus.
Read more at: newscientist.com
