Primordial electrical storms might have helped provide a key building block to initiate life on Earth, according to a study published March 16 in Nature Communications.
Phosphorus is an essential element for all known life, forming the backbone of DNA and RNA molecules. Although the element was abundant on ancient Earth, most of it was locked inside nonreactive minerals. This had led researchers to hypothesize, in a 2005 study, that meteorites were responsible for the delivery of reactive phosphorus in the form of the mineral schreibersite, according to NPR.
But the origins of life on Earth might have been home grown. A team of geologists discovered that lightning strikes here on our planet can form schreibersite.
That means the “emergence of life is not necessarily connected to meteorite impacts,” Sandra Piazolo, a geologist at the University of Leeds in England and a coauthor of the study, tells Science News.
When a lightning bolt hits the ground, it can create glassy rocks called fulgurites. Using X-ray and light spectroscopy to analyze a piece of fulgurite created by a 2016 lightning strike in Illinois, the researchers found tiny spheres of schreibersite dotted throughout the rock. They calculated that lightning had formed a steady supply of about 110–11,000 kilograms of phosphorus-containing compounds per year on ancient Earth, around 3.5–4.5 billion years ago.
The team also estimated that 4.5 billion years ago, meteorites supplied about 100,000–10 million kilograms of phosphorus-containing compounds, but this dramatically fell over time as fewer of these rocks bombarded Earth. So whether meteorites or lightning were more important sources of phosphorus may depend on when life evolved. It’s thought that the earliest lifeforms made their debut at least 3.5 billion years ago, but it’s difficult to pinpoint the exact time point, according to Science News.
“If life is a little bit younger, then lightning is a fantastic source of phosphorus,” Matthew Pasek, a geochemist at the University of South Florida in Tampa who was not involved in the research, tells Science News. “If it’s older, then meteorites were a much more abundant source.”
Although it’s difficult to say if meteorites or lightning supplied phosphorus for life on Earth, the study identifies a potential source of the element for other planets.
“It’s really nice . . . to be able to say there’s more than one path to generating phosphorous that could be available to a planet that might be able to develop life,” Hilairy Hartnett, an astrobiologist at Arizona State University who was not part of the study, tells NPR.