A lightning strike may have helped spark life on earth — here’s how

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The origin of life on Earth is one of the most complex puzzles facing scientists. This is not only to identify the many chemical reactions that must take place to create a replicating organism, but also to find realistic sources for the ingredients necessary for each of the reactions.

A particular problem faced by longtime scientists studying the origin of life is the source of the elusive element, phosphorus. Phosphorus is an important element for basic cell structures and functions. For example, it forms the backbone of the double helix structure of DNA and associated molecular RNA.

Although the element is widespread, almost all of the phosphorus in early Earth – around 4 billion years ago – was trapped in minerals that were essentially insoluble and unreactive. This means that phosphorus, although present in principle, was not available to make the compounds necessary for life.

In a new article, we show that lightning strikes would have provided a widespread source of phosphorus. This means that lightning strikes may have helped start life on Earth and may continue to help start life on other Earth-like planets.

One potential source of phosphorus on early Earth is the unusual mineral schreibersite, which is found in small amounts in meteorites. Experiments have shown that schreibersite can dissolve in water, creating aqueous phosphorus which can react and form a variety of organic molecules important for life. Examples include nucleotides, the building blocks of DNA and RNA, and phosphocholine, a precursor of lipid molecules that make up the cell membrane.

But there is another potential source of schreibersite. By studying a glass structure created by a lightning strike called fulgurite, we found a substantial amount of the unusual mineral phosphorus inside the glass.

If lightning created a large amount of schreibersite and other reactive phosphorous minerals, lightning could be an alternate source of the reactive phosphorus necessary for life.

To determine if this was the case, we estimated the amount of phosphorus made available by lightning 4.5 billion years ago, when Earth formed, to 3.5 billion years ago, when we have the first fossil evidence of life.

A sample of fulgurite glass on the ground.