Could Life On Earth Have Come From A Comet?

What if alien DNA led to human existence? This amino acid recently found in comets gives us insight on our potential alien-relatives.


If you saw the 2012 sci-fi film “Prometheus” … you have our sympathies. That movie — a kinda-sorta prequel to the “Alien” franchise from director Ridley Scott — is truly impenetrable. On the upside, “Prometheus” did introduce the concept of panspermia to the general movie-going audience, and that’s a useful thing.

As it happens, it’s also what our intrepid space producer Ian O’Neill is digging into with today’s DNews dispatch.

Panspermia refers to the theory that life on Earth actually originated in outer space, and was brought here by way of microorganisms, chemicals, germs or spores distributed by asteroids or comets.

It’s a wild idea, but not as crazy as you might think. As Ian explains in the video, there’s actually quite a bit of debate as to precisely where life’s building blocks came from. We have a pretty good notion that life started popping up on Earth about 3.5 billion years ago. But were the ingredients for life — the prebiotic chemicals required for living organisms — already here? Or were they dropped here by interplanetary delivery?

Scientists rooted out an important clue recently, when the European Space Agency’s Rosetta spacecraft detected the amino acid glycene in atmosphere around Comet 67P. That’s the second time we’ve found glycene in the vicinity of a comet, and it’s a Pretty Big Deal.

That’s because glycene is one of the essential building blocks for life — as we know it, anyway — and finding it on two different comets suggests that finding it on the first comet wasn’t a fluke. Further exciting astrobiologists is the fact that Rosetta’s comet contains other compounds that form the essential structure of organic life, including phosphorous, the chemical backbone of DNA and RNA.

These discoveries indicate that the ingredients for life can potentially be found all over the universe, catapulted from planet to planet by comets. The panspermia hypothesis takes things a step further and posits that life itself can survive interstellar jaunts. What if Earth’s first little wriggling things came from space?

Well, it opens up a whole new universe of possibilities, really. Consider the reverse scenario: What if, after life developed on Earth, a chunk our planet flew off into space with bacteria hitching a ride? If those little wrigglies dropped onto another planet, they could possibly take root. That’s a theory called lithopanspermia.

The additional syllables just keep coming: Necropanspermia suggests that life could hop from planet to planet even if it dies en route. Fossilized DNA in such a scenario could still create a template for organic chemicals to grab onto, mimic, and generate life.

Then there’s the concept of directed panspermia — the “Prometheus” scenario — which involves advanced alien civilizations deliberately seeding life around the cosmos. In this case, aliens might just sprinkle a few custom amino acids around young, developing stars. Wait a few billion years and, kapow! You have seven billion homo sapiens running around, wondering how they got there.

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