How did life begin? It’s one of the most profound questions in science. Evolution explains how life changes over time, but before evolution could even start, something had to create the very first biological building blocks.
For life to emerge, Earth needed certain molecules: organic compounds containing carbon and nitrogen. Yet, for hundreds of millions of years after the planet formed, these molecules were nowhere to be found. A new study finally suggests where they came from.
Specifically, the research argues these compounds formed through microlightning – tiny, unseen sparks of electricity generated when water droplets break apart.
This process happens constantly in nature, from ocean waves crashing against the shore to the spray of a waterfall. According to the research, these minuscule bursts of energy could have driven the chemical reactions that produced life’s first essential ingredients.
“To get life, we need carbon and nitrogen bonds,” said Prof Richard Zare, co-author of the study published in Science Advances, speaking to BBC Science Focus. “These bonds are needed to make amino acids (the building blocks of proteins) and nucleic acids (the building blocks of DNA and RNA).”
For decades, one of the leading theories about life’s origins was the Miller-Urey hypothesis.
In a famous 1952 experiment, scientists Stanley Miller and Harold Urey showed that exposing a mixture of gases – thought to resemble Earth’s early atmosphere – to electricity could produce organic molecules. The idea was that lightning strikes into the ocean may have jump-started the chemistry of life.
However, some scientists have criticised this theory, pointing out that lightning is relatively rare and the ocean too vast for these reactions to happen frequently enough.
The new study offers an alternative: perhaps life’s building blocks weren’t formed in one dramatic lightning strike but through countless tiny electrical discharges happening all around the planet, all the time.
Zare and his team set out to investigate this possibility. They examined how water droplets acquire different electrical charges when they break apart, finding that larger droplets tend to carry a positive charge while smaller ones are negatively charged.
When these oppositely charged droplets come into contact, they release a tiny spark – the phenomenon Zare calls microlightning.
Though these flashes are too small to see with the naked eye, they still carry significant energy.
To test their impact, the researchers sprayed room-temperature water into a gas mixture containing nitrogen, methane, carbon dioxide and ammonia – all believed to be present on early Earth.
The result? The formation of key organic molecules, including hydrogen cyanide, glycine (the simplest amino acid), and uracil (a building block of RNA).
The implications of this discovery go beyond just understanding life’s origins. If microlightning can produce complex molecules from simple ingredients, it could be playing a role in many other natural chemical processes.
Zare believes that the chemistry of tiny water droplets is an underexplored frontier in science. “We’re only just scratching the surface of the kind of chemistry happening at interfaces,” he said. “Often chemists are busy talking about what happens to the bulk, but what’s going on at the surface is what’s really exciting, and people don’t pay much attention to that.”
Indeed, this research highlights how seemingly insignificant, everyday processes – like the mist of a waterfall or the spray of ocean waves – could hold the key to life’s deepest mysteries.
About our expert
Richard Zare is a renowned chemist and professor of natural science at Stanford University. His research, published in prestigious journals such as Science and Nature Nanotechnology, has been cited over 100,000 times. Zare's dedication to research and teaching has been recognised by many awards, including the National Medal of Science, the Wolf Prize in Chemistry and the Presidential Award for Excellence in Science, Mathematics and Engineering Mentoring. He is also the recipient of 11 honorary doctorates.
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