March 5, 2024

Can we recreate the spark of life on Earth?

Some 4.5 billion years ago, the newly formed planet Earth was devoid of animals, plants and bacteria. Yet just a few hundred million years later, the first primitive life forms emerged. How exactly this happened is one of science’s greatest mysteries, but we may be closer than ever to finding out what sparked it.  And now researchers are making strides at recreating the process in the lab.

When the planet first formed, conditions on Earth were too inhospitable for life; violent volcanic eruptions spewed hydrogen sulphide into the atmosphere, there was little oxygen, and the planet faced frequent bombardment from asteroids.

Yet we know that as little as 200 million years later, Earth was a much more welcoming place. Fossil records show that the world was brimming with simple single-celled organisms from around 3.7 billion years ago. So how did these first lifeforms get going?

There’s a consensus that for life to exist you need organic, carbon-containing compounds like methane, coupled with water and a source of energy. This spark would kickstart the chemical reactions needed to create more complex molecules, such as amino acids – the building blocks of proteins, and RNA – a nucleic acid present in all living cells with structural similarities to DNA. But what provided the spark, and could we recreate it?

Lightning storms

One idea is that intense ultraviolet radiation and lightning present on the early Earth could have provided the energy for amino acids, and later molecules such as DNA and RNA to form in the oceans.

Support for this theory came in 1952, when University of Chicago graduate student Stanley Miller teamed up with Harold Hey, a Nobel laureate in chemistry, to try to recreate the atmospheric conditions of early Earth. They injected ammonia, methane and water vapour into an enclosed glass container, then passed an electrical spark through the beaker to simulate a lightning strike. Amazingly, amino acids spontaneously formed. However, later research showed that the atmospheric conditions modelled by Miller and Hey were unlikely to have existed on Earth at the time. Another problem is that for four billion years the planet was mostly covered with ice, and lightning rarely strikes in such conditions.

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However Jeffrey Bada, a former student of Miller, and a professor of marine chemistry at the Scripps Institution of Oceanography in San Diego, believes that that lightning could have formed within volcanic ash clouds. There is good reason to think that such conditions produce intense lightning storms. In 2022, the underwater volcano Hunga Tonga–Hunga Haʻapai in the southern Pacific Ocean erupted and spewed a mix of gases, ash, and seawater vapour 33 miles (52.8km) into the atmosphere. The result was a stunning 25,508 lightning strikes in just five minutes.

“There were a lot of small volcanic islands on the early Earth,” argues Bada. “I suspect these volcanoes were erupting quite violently, and there were a lot of them.”

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