Siberia explosion in 1908

"New evidence from an unlikely source -- water vapor in the exhaust plumes of space shuttles launched a century later -- points to a comet."

Just last year, many experts were figuring it was an asteroid.

But Kelley's team thinks a comet fits better, since comets are loaded with water ice (asteroids are mostly rock and metals). The comet would have started to break up at about the same altitude as the release of the exhaust plume from the space shuttle following launch, they calculate. In both cases, water vapor was injected into the atmosphere.

But how did the water vapor travel so far?

"There is a mean transport of this material for tens of thousands of kilometers in a very short time, and there is no model that predicts that," Kelley said. "It's totally new and unexpected physics."

Kelley and his colleague say a new model of upper-atmospheric physics is needed. They propose counter-rotating eddies with extreme energy. Once the water vapor got caught up in these eddies, it traveled very quickly -- close to 300 feet per second, they write in the June 24 issue of the journal Geophysical Research Letters.

This got me wondering: If vapor can travel down so fast, can it also travel up at the same speed? Can other gases or particles be injected into or dejected from the atmosphere at this speed?