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The conventional wisdom is that Earthly life began… on Earth. A few decades ago, many scientists believed (as did Charles Darwin) that terrestrial life first appeared in "some warm little pond." Today’s astrobiologists are less fond of ponds, and more likely to suggest that biology began in the hot, sulfurous thicket of a deep sea vent.
But there is a controversial alternative to this life from hell scenario. It’s life from heaven. Or if not from heaven, at least from the stars.
About 25 years ago, two British astronomers, Fred Hoyle and Chandra Wickramsinghe, proposed that comets might be the Johnny Appleseeds of life, carrying vital spores from star system to star system, an idea that is known today as panspermia. If the tail of such a life-loaded comet were to brush the Earth, it might pass some of its frozen microorganisms into the atmosphere where they could descend to our planet’s surface. The two astronomers ventured that this might account for the start of life on Earth.
They also made the disturbing suggestion that panspermia could spread disease.
Now you might wonder whether life from space, as intriguing as the idea might be, solves the mystery of how biology got started in the first place. Or does this theory merely push the problem of life’s origin into someone else’s lap?
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