According to calculations by American and British scientists, lightning strikes could provide enough of the necessary phosphorus compounds to support the first life on Earth. The results of the study are published in the journal Nature Communications.
For life to arise on Earth as we know it, we need a precisely balanced set of primary elements. One of them is phosphorus, a key component of DNA, RNA, and lipids in cell membranes, which must be bioavailable, i.e., in a reactive, soluble form, to be incorporated into organic molecules.
But all the nonbiogenic phosphorus on Earth is contained in insoluble minerals. The only exception is schreibersite (Fe, Ni) 3P, which is present in meteorites. Therefore, until now, it was believed that prebiotic phosphorus hit the Earth during an early meteor bombardment.
Researchers from Yale University in the US and the University of Leeds in the UK have proposed an alternative source of schreibersite and its phosphorus. After studying fulgurites-structures formed in rocks at the sites of lightning strikes and composed mainly of caked silica-the authors used spectroscopic methods to detect schreibersite in the form of glassy formations.
“This work has helped us understand how life could have formed on Earth and how it is still forming on other Earth-like planets. In part, it all starts with phosphorus,” the first author of the article, Benjamin Hess, is quoted in a press release from Yale University.
Scientists conducted simulations that showed that in the billion years that passed from the formation of the Earth to the appearance of the first organic forms, lightning could produce enough bioavailable phosphorus in the form of phosphide, phosphite, and hypophosphite to give rise to early life on Earth.
Today, there are approximately 560 million lightning flashes per year on Earth. Based on the higher electrical activity of the early atmosphere, the authors estimate that between one and five billion lightning flashes occurred annually on Earth in the early stages, of which between 100 million and one billion reached Earth. For a billion years, this is from 0.1 to one quintillion beats.
By estimating the amount of schreibersite that could have formed at each impact, and the land area of the early Earth, the scientists, obtained between 110 and 11,000 kilograms of reactive phosphorus per year. In their opinion, this is, in any case, more than from the fall of meteorites and quite enough to support the first forms of life.
The authors of the article note that the hypothesis of the origin of prebiotic phosphorus in lightning strikes has many advantages over the “meteorite” hypothesis. First, the number of lightning strikes for hundreds of millions and billions of years remains at the same level. The mass falls of meteorites were timed to separate, relatively short periods in the history of the Earth. Secondly, lightning is more common in tropical regions, where, in theory, the origin of life occurred.
According to the researchers, the presence of electrical discharges in the atmosphere can be an important sign for the search for life on other planets.