Here’s something to really bake your noodle: A bunch of scientists are now theorizing that SARS might have arrived on Earth from another planet.

I am not kidding. From NationalGeographic.com:

In a letter to the British medical journal The Lancet, Chandra Wickramasinghe, from Cardiff University in Wales, and other scientists, propose that SARS may have originated in outer space then fallen down to Earth and landed in China, where the outbreak began.

It sounds like a headline from a supermarket tabloid, but the idea may not be as outlandish as it first appears. One hundred tons (90 metric tons) of space debris fall on Earth every day; some scientists believe as much as one ton (0.9 metric ton) of bacteria from space is part of that daily deposit.

Particles carrying the SARS virus could have come from a comet, the researchers say, and released into the debris trail of the comet’s tail. The Earth’s passage through the stream would have led to the entry of the culprit particles.

“We’re not saying this is definitely what happened,” said Wickramasinghe, who is also the director of the Cardiff Centre for Astrobiology, a research effort that seeks evidence of extraterrestrial life. “But the theory should not be ruled out.”

Okay, I guess you can take or leave this question of whether SARS could have come from little green men. But let’s back up a bit: One ton of bacteria falls from space every day? One ton? Of space bacteria? EVERY DAY?? Why haven’t we been, you know, like, told about this kind of thing?

Mind you, not everyone is convinced of this SARS-UFO theory:

“We have no scientific evidence that SARS or any other infectious disease has dropped off a meteor at this point in time,” Julie Gerberding, director of the Atlanta-based Centers for Disease Control and Prevention, said at a recent briefing. “Should we discover any evidence supportive of that, we would let you know.”

(Thanks to Chris for this one!)