Last February, Mika-Pekka Markkanen went ice skating. "I came across this fantastic opportunity to skate on the natural untouched ice of a pond by the sea, surrounded by mountains on the Arctic island of Senja, Norway," says Markkanen. He stepped on the ice and witnessed a mystery that has stumped experts for more than a year. 

Mika-Pekka Markkanen

"I noticed these strange colors near the sun's bright reflection on the ice," says Markkanen. "Luckily I had my camera and tripod so I managed to capture some nice photos of the phenomenon."

What caused the rainbow-like colors? Markkanen looked for help, contacting many experts in the field of color and atmospheric optics. "Nobody seemed to have clear answer. No one, not even Les Cowley, had ever even seen such a thing before!"

Finally, Dietrich Zawischa, a retired professor from the Institute of Theoretical Physics of Hannover University, may have found an answer. Using computer simulations, he modeled the colorful arcs as an interference pattern created by fine grains on the surface of the ice.


Zawischa's model of the interference phenomenon

"Such beautiful natural ice is very rare, and I guess that this optical effect is so uncommon that it has not yet been named," says Zawischa. "The grainy surface texture of the ice appears to be responsible for the colors. The texture might be due to snow falling just when the water was going to freeze while the weather was very calm. Presumably, rays of sunlight reflected by neighboring grains interfere."

"Although I was not able to reach full agreement between the photo and the simulation," says Zawischa, "I think we have captured the essential physics of the phenomenon."
Bron: http://www.spaceweather.com/