© Howard Cohen
Photo details: Canon EOS 5D Mark II, 190 seconds, ISO 800
On April 5th, space shuttle Discovery blasted off from Cape Canaveral at the crack of dawn. The shuttle began its journey in darkness--the sun was still below the horizon--but moments after it left the pad, Discovery burst into high altitude sunlight and proceeded to put on an extraordinary show. University of Florida astronomy professor Howard Cohen describes what he saw from his home in Gainesville, more than 130 miles from the Cape.

"The launch began in typical fashion- a brilliant, yellowish glow rising out of the southwest gradually morphing into a white contrail. Impatient observes might have thought that was it. But then an amazing contrail, the likes of which I have never seen before, rapidly appeared around and following the shuttle's path. For a short time it resembled a comet streaking across the dawn sky." He took this picture using his Canon EOS 5D.

"In binoculars the view was stunning and chilling," Cohen continues. "It was like viewing a comet traveling in fast motion -- I could see the contrail unfolding, glistening and wavering behind the shuttle. Unlike some who might have thought something might have gone wrong, this never entered my mind. I could easily see the shuttle unhesitatingly moving forward."

Atmospheric optics Les Cowley believes the cloud formed when the shuttle entered the mesosphere. Water vapor spewing from the shuttle's main engines began to freeze, forming crystals of just the right size to scatter sunlight and produce the iridescent colors shown in so many photos.

"I think we had a 'perfect storm' for this launch," concludes Cohen. "Atmospheric conditions including probably cold and moist air, clear skies and especially sunlight at just the right angle produced this unique effect. Unfortunately, with the shuttle program coming to an end, we probably will not see this again."