Primordial rays may have helped life emerge on Earth

The appearance of the first living organisms on Earth billions of years ago may have been facilitated by lightning out of nowhere, or perhaps a trillion of them.

Researchers said Tuesday that lightning during the first billion years after the planet’s formation roughly 4.5 billion years ago may have released the phosphorus necessary for the formation of biomolecules essential for life.

The study may offer insight into the origins of Earth’s earliest microbial life and possible extraterrestrial life on similar rocky planets. Phosphorus is a fundamental part of life’s recipe. It forms the phosphate backbone of DNA and RNA, hereditary material in living organisms, and represents an important component of cell membranes.

On early Earth, this chemical element was locked up within insoluble minerals. Until now, meteorites that bombarded early Earth were widely thought to be primarily responsible for the presence of “bioavailable” phosphorus. Some meteorites contain the phosphorus mineral schreibersite, which is soluble in water, where life is believed to have formed.

When lightning strikes the ground, it can create glassy rocks called fulgurites by overheating and sometimes vaporizing the rock from the surface, releasing the phosphorous locked inside. As a result, these fulgurites can contain schreibersite.

The researchers calculated the number of rays that extended between 4.5 billion and 3.5 billion years ago based on the atmospheric composition at the time and calculated the amount of schreibersite that could result. The upper range was about a trillion rays and the formation of more than a billion fulgurites per year.

The phosphorus minerals that emerge from the lightning eventually exceeded the number of meteorites about 3.5 billion years ago, about the age of the first widely accepted fossils known as microbes, they found.

“Lightning, therefore, may have been a significant part of the emergence of life on Earth,” said Benjamin Hess, a Yale University graduate student in earth and planetary sciences and lead author of the study published in the journal Nature. Communications.

“Unlike meteorite impacts that diminish exponentially over time, lightning strikes can occur at a sustained rate throughout a planet’s history. This means that lightning can also be a very important mechanism for providing the necessary phosphorous for the emergence of life on other Earth-like planets after meteorite impacts have become rare, ”Hess added.

The researchers examined an unusually large and pristine sample of fulgurite that formed when lightning struck the backyard of a home in Glen Ellyn, Illinois, outside of Chicago. This sample illustrated that fulgurites harbor significant amounts of schreibersite.

“Our research shows that the production of bioavailable phosphorus by lightning may have been underestimated and that this mechanism provides a continuous supply of material capable of delivering phosphorus in a form appropriate for the onset of life,” said study co-author Jason Harvey. . Associate Professor of Geochemistry at the University of Leeds.

Ingredients considered necessary for life include water, carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus, along with an energy source.

Scientists believe that the first bacteria-like organisms arose in Earth’s primordial waters, but there is debate as to when it occurred and whether it developed in warm, shallow waters or in deeper waters in hydrothermal vents.

“This model,” Hess said, referring to phosphorus released by lightning, “is applicable only to the terrestrial formation of life, such as in shallow waters. The phosphorus added to the ocean by lightning would probably be negligible given its size. “

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