A Meteor Strike Might Be Responsible For Life On Earth

You may not have heard of the Miller-Urey experiment, but it makes an appearance in virtually every high school biology textbook. Basically, it shows that sending a small jolt through an atmosphere like that of early Earth sparks the production of certain key amino acids that are necessary for life. The problem is that since the experiment was developed in 1954, we've learned a lot more about what early Earth was like, and have realized that Miller-Urey doesn't tell us as much as we thought it did. Now, a new take on the experiment might clarify the origins of life even further.

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A New Paradigm

So what's changed in the past half century? For one thing, we've come to realize that those amino acids that the Miller-Urey experiment produces aren't nearly so necessary to—and certainly not sufficient for—life as we thought. While it's true that they could form the proteins that can trigger cell reactions, it turns out that proteins aren't the only way to do that. The genetic messenger known as RNA can set off some key reactions as well. If those proteins happened to be around to participate in the initial spark of life, they'd have certainly come in handy, but on their own they wouldn't be enough to get the ball rolling.

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There's also the matter of the Earth's atmosphere. Miller and Urey assumed that the Earth at the time would have a "reducing" atmosphere—as Ars Technica explains, that means that the major molecules of the atmosphere would be linked to hydrogen atoms, "so ammonia instead of molecular nitrogen, water and methane instead of carbon dioxide, and no oxygen on its own." But most modern scientists believe that early Earth's atmosphere would have been closer to neutral—not too much hydrogen, not too much oxygen—and that could create the foundation for a very different set of building blocks. But assuming that the atmosphere was on the reducing side of neutral, and with the knowledge that the frequent comet collisions of the era would have carried reduced chemicals, the new team thought that the reducing atmosphere of Miller-Urey would still have been relevant. But that thing about the comets gave them an idea.

The Crater Of Life

When the new team ran the experiment, they were looking for one specific chemical known as formamide, a simple molecule that can react with itself to form the four bases of RNA. They found it in abundance and celebrated their success, though the formamide did not actually turn into those essential RNA building blocks. But a new method presented itself when they realized they had access to technology that could mimic the shockwave of a massive impact: the Prague Asterix Laser System, which can create massive pulses of energy.

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When they tested this method out, they discovered that not only had they produced formamide again, but the formamide had spontaneously formed all four RNA bases. That means that even if our genetic material didn't originally hitch a ride on a comet, the primordial soup still might have been stirred with an interplanetary spoon, so to speak. If the environment of early Earth was able to produce both RNA bases and amino acids, it's only a matter of time before the origin of life is finally revealed.


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Written by Curiosity Staff April 27, 2017
