Giant Ginkgo

Top investigators of the Columbia space shuttle disaster are analyzing a startling photograph -- snapped by an amateur astronomer from a San Francisco hillside -- that appears to show a purplish electrical bolt striking the craft as it streaked across the California sky.

The digital image is one of five snapped by the shuttle buff at roughly 5: 53 a.m. Saturday as sensors on the doomed orbiter began showing the first indications of trouble. Seven minutes later, the craft broke up in flames over Texas.

In the critical shot, a glowing purple rope of light corkscrews down toward the plasma trail, appears to pass behind it, then cuts sharply toward it from below. As it merges with the plasma trail, the streak itself brightens for a distance, then fades.

The lab has been listening to the sounds of ghostly electromagnetic phenomena in the upper atmosphere, dubbed sprites, blue jets and elves. For some time, scientists have speculated on whether these events could endanger airliners or returning spacecraft.

A study conducted 10 years ago for NASA found that there is a 1-in-100 chance that a space shuttle could fly through a sprite, although it concluded that the consequences of such an event were unclear. And in 1989, an upper-atmospheric electrical strike "shot down" a high-altitude NASA balloon 129,000 feet over Dallas.