Not about Charlie Sheen ...

... Except to the degree it's true of each of us.

Panspermia (from the Greek, literally "all seed") is the hypothesis that primitive life exists throughout the universe and thus that life on Earth may have originated elsewhere. Panspermia theory doesn't contradict evolution, because evolutionary theory deals with how life changes, not how (or where) it began.

Did life come to Earth on, say, a meteorite? While panspermia is not exactly the scientific mainstream, it has had prominent advocates over the centuries, including physical chemist Svante Arrhenius, physicist Lord Kelvin (aka, William Thomson), and astronomer Sir Fred Hoyle. It's commonly accepted that organic chemicals are widely dispersed in space, but there's been no proof of extraterrestrial life. (In 1996 President Clinton made a statement to announce NASA might have found fossilized bacteria in a meteorite of Martian provenance ...

but those findings were later downgraded to inconclusive.)

Now there's a new (March 5th) report: Exclusive: NASA Scientist Claims Evidence of Alien Life on Meteorite. These latest findings are from Dr. Richard B. Hoover, an astrobiologist at NASA’s Marshall Space Flight Center.  Briefly, he reports finding microstructures within a meteorite reminiscent of cyanobacteria. Ditto biochemicals.

Haven't heard a thing about it? Far from the fanfare of the Martian-meteorite announcement, this report is, so far, largely ignored (and when acknowledged, widely dismissed). Because of the once-burned-twice-shy principle? Maybe. Some of the skepticism (Scientists Dubious Over Claim of Alien Life Evidence in Meteorite) is on the petty side: "It [the Journal of Cosmology] doesn't exist in print, consists entirely of a crude and ugly website that looks like it was sucked through a wormhole from the 1990s ..." says P.Z. Myers, a biologist at the University of Minnesota, Morris. The aesthetics of the web design -- yeah, that's what's important here.

Here is Hoover's article at Journal of Cosmology, if you want to take a look: Fossils of Cyanobacteria in CI1 Carbonaceous Meteorites

Am I convinced? Not yet. The meatier (heh!) objection to the finding is that the semblance to bacteria is to cyanobacteria -- aka, blue-green algae. On Earth such single-celled lifeforms live in water and produce oxygen -- luckily for you and me. That doesn't sounds like the environment inside an ancient meteoroid. (Meteoroids are in space; they change names to meteorites when they fall to Earth.) But an apparent planetary origin is not necessarily a show-stopper: celestial impacts move rocks between planets all the time. That's how the Martian meteorite of the 1996 announcement came to be found in Antarctica.)

We're learning more every day about how hardy life, especially primitive life, can be. Extremophiles have been found that thrive in boiling water, in radioactive environments, in strong acids, and in the pores of deep rock. Earthly bacteria can stay dormant for long times and then be revived. See: Bacteria: The Space Colonists for an interesting article and lots of citations.

Has the recent announcement convincingly proved anything about panspermia? No, but neither has anything been disproved. Stay tuned.