Waves crashing against the rocks sprays water into the air at a beach in Greece. a_Taiga / iStock / Getty Images Plus
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Stanford University researchers have discovered that small bursts of electricity — which they call microlightning, created by oppositely charged water droplets interacting in the early Earth, likely created the first organic compounds that later led to life.
For decades, one of the leading hypotheses for the origin of life has been the Miller-Urey hypothesis. In 1952, renowned chemist Harold Urey observed that most planets in the solar system were dominated by nitrogen and methane, and posited that early Earth’s atmosphere likely did as well.
However, as Richard Zare, the study’s senior author and head of Stanford University’s Zare lab where the experiment was conducted, told EcoWatch, life needs carbon-nitrogen bonds to form essential molecules like DNA and RNA, and these bonds would have been completely absent from the early Earth.
Urey, later that same year, along with Stanley Miller, carried out an experiment to test whether Earth could have created these bonds. They used an apparatus with a glass bulb to simulate Earth’s atmosphere, composed of nitrogen, methane and other gases. Then, using a spark plug, they simulated lightning in the atmosphere, and successfully created carbon-nitrogen-bonded organic molecules in the apparatus, thought to be precursors to life.
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While the results were groundbreaking, they were not without objections, Zare told EcoWatch. “One of them is that lightning is intermittent and unpredictable,” he said. “And I believe that’s true. And if lightning makes compounds in the atmosphere, the atmosphere is a big thing. They never get concentrated… we need to concentrate these building blocks because we’re making small building blocks.”
But what if Earth didn’t need large lightning strikes at all to create these compounds? That’s the question Zare et al. set out to answer. The study’s lead author, Yifan Meng, carried out the experiment, similar to the Miller-Urey experiment, but on a much smaller scale, still using gases present on early Earth roughly 4.5 billion years ago, but using microlightning created by water droplets rather than big sparks.
“We have repeated what Miller and Urey did before, but they did it with big lightning, in a bulb. We’ve done it with water droplets,” Zare said. “And so we propose that this is a new mechanism for the prebiotic synthesis of molecules that constitute the building blocks of life.”
The researchers suspended a large droplet of water in air using sound waves. When the sound wave generator was turned off, the levitated water droplet fell and struck a plastic sheet below, causing the water droplet to split into smaller droplets, creating a splash of droplets that interacted with one another, creating sparks of microlightning.
When that microlightning was created in the presence of gases present on early Earth, the electrical discharge interacted with gas and successfully created organic compounds with carbon-nitrogen bonds.
Zare said these interactions are happening constantly in our world, creating microlightning and organic compounds, but are much less consequential than the first time this microlightning created organic molecules billions of years ago.
He added that he wants to continue researching how water droplets interact, and hopes that they can one day be used to clean up our atmosphere.
“I actually am very interested in possibly removing pollutants in our atmosphere with water droplets,” Zare said, “such as can we bubble air through water and remove things like carbon dioxide and methane and turn them into something else? I’m interested in all this. So you ask, what is the future? Many, many futures here.”
Micron-sized water droplets could also provide a sustainable way to create ammonia, which is important for fertilizer and combating global hunger. Zare said that we may be able to scale up the gas-droplet experiment, which creates ammonia as a byproduct, and in doing so, we could replace the Haber-Bosch process of creating ammonia, which is harmful to the environment.
“The Haber-Bosch process takes nitrogen and hydrogen and and combines it to make NH3. That’s ammonia. And where does the hydrogen come from? They get it from natural gas, from methane, by treating it with steam, with hot water vapor under high pressure, high temperature. And the result is the natural gas turns [in part] into CO2,” Zare said.
“And so, believe it or not, 2% or so of the CO2 that you and I now breathe comes from the Haber-Bosch process in the atmosphere. That’s how big this has been. If you could clean up the Haber-Bosch process, you would really make a difference in terms of climate change as we understand it.”
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