Question

Could life have originated elsewhere in the universe and flown through space to Earth?

Panspermia, the theory that life originated not on Earth but was carried here through millions of years in space, has existed as public terminology since before the 1970's. Introduced formally by astronomers Fred Hoyle and Chandra Wickramasinghe, the theory postulates that tiny "spores," literally well-preserved seeds of living organisms, were trapped in asteroids and comets from their place of origin and deposited on the surface of our planet via meteorites. Most scientists, such as Jay Melosh of the University of Arizona, concede that comets and large meteors could potentially protect bacteria and viruses from the hazardous radiation experienced in interstellar space. Moreover, the extremely cold temperatures of such comets could preserve these spores in blocks of ice. Comets carrying this frozen material could have also brought water to the Earth. Nevertheless, though a plausible description of the origin of life on Earth, few astrobiologists accept it as truth. Why? Well, in part, the probability of an Earth-sized planet crossing paths with these rare meteors is miniscule, as only "about one meteorite ejected from a planet belonging to our Solar System is captured by another stellar system every 100 million years," says Melosh. Recent experiments by NAI microbiologist Rocco Mancinelli have shown that the severe conditions in space, extreme dessication and powerful UV radiation, are not enough to permanently kill a bacterium. He flies populations of bacteria on the space shuttle, exposes them to the conditions of open space, and is still able to revive them upon their return to Earth. So perhaps primitive life forms did indeed fly through space, dried-out and dormant, and when they reached a planet that happened to have suitable conditions for revival, flourished and prospered. For related articles, check out these non-NASA websites: http://www.spaceref.com/news/viewpr.html?pid=4115 and http://www.spaceref.com/redirect.ref?url=www.planetary.org/html/news/articlearchive/headlines/2000/Panspermia.htm&id=2923 or visit the official panspermia website at www.panspermia.org.
May 1, 2002