Dr. Frankenstein might not have needed a lightning bolt to bring his monster to life after all. A new study from Stanford suggests that life might have been kickstarted by constant zaps from “microlightning” between water droplets.
The most profound missing link in the evolutionary tree is the very first one: how did living cells arise from non-living matter? It’s thought that early Earth contained a primordial soup of ingredients essential for biology as we know it – all it needed was a specific catalyst to kick off the chemical reactions to turn inorganic compounds organic.
One of the most enduring ideas is that lightning strikes could have provided that spark. The seminal 1952 Miller-Urey experiment sent jolts of electricity through a flask of water and gases intended to represent early Earth’s atmosphere, and found that certain amino acids and other important biological molecules were produced.
But there are a few problems with the hypothesis. If this process occurred in the oceans, the chemicals created would be too diluted to widely kickstart life. If it happened in shallow ponds, the chances of a lightning strike in that small a space is remote.
For the new study, Stanford scientists suggest that the electrical energy could have come from a far more common and consistent source – what they call microlightning. When water droplets are sprayed into the air, from waves or waterfalls or the like, small electric charges can form between them. These tiny zaps can set off the complex chemistry without need of any external electricity.
“Microelectric discharges between oppositely charged water microdroplets make all the organic molecules observed previously in the Miller-Urey experiment, and we propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life,” said Richard Zare, senior author of the study.
To test the idea, the researchers ran an updated version of the Miller-Urey experiment. It started with a tank full of gases meant to mimic early Earth, including nitrogen, methane, carbon dioxide and ammonia. Into this mix they sprayed fine droplets of room-temperature water.
On closer inspection, they found that larger droplets tended to carry a positive charge, while smaller ones were negative. As basic physics tells us, when droplets with opposite charges pass close to each other, tiny bolts of electricity jump between them.
While they’re too fast to be seen normally, the researchers were able to capture this microlightning using high-speed cameras, confirming that it does occur.
Importantly, in the ancient atmosphere sample, sprays of water alone were enough to ionize the air and trigger the formation of organic molecules with carbon-nitrogen bonds, such as hydrogen cyanide, glycine and uracil. These bonds are among the most common in organic chemistry, and the molecules they appear in provide the building blocks of proteins and DNA.
“Given that lightning is an intermittent and unpredictable phenomenon, whereas water sprays are so common on Earth, we suggest that our results provide another possible pathway for the abiotic formation of carbon-nitrogen bonds,” the researchers write.
This means that waves, waterfalls and other sprays could have churned up a huge amount of organic compounds all over the planet, and these building blocks could eventually start stacking into the earliest lifeforms.
The research was published in the journal Science Advances.
Source: Stanford University