A new study suggests that lightning helps make an essential element available to organisms in habitable environments.
The search for life on other planets is a lot like cooking. (Bear with me for a second.) You can have all the ingredients in one place—water, a warm climate and thick atmosphere, the proper nutrients, organic material, and a source of energy—but if you don’t have any processes or conditions that can actually do something with those ingredients, you’ve just got a bunch of raw materials going nowhere.
So sometimes, life needs a spark of inspiration—or maybe several trillion of them. A new study published in Nature Communications suggests lightning may have been a key component in making phosphorus available for organisms to use when life on Earth first appeared by about 3.5 billion years ago. Phosphorus is essential for making DNA, RNA, ATP (the energy source of all known life), and other biological components like cell membranes.
“This study was actually a lucky discovery,” says Benjamin Hess, a Yale University researcher and lead author of the new paper. “It opens up new possibilities for finding life on Earth-like planets.”
This isn’t the first time lightning has been suggested as a vital part of what made life possible on Earth. Lab experiments have demonstrated that organic materials produced by lightning could have included precursor compounds like amino acids (which can join to form proteins).
This new study discusses the role of lightning in a different way, though. A big question scientists have always pondered has to do with the way early life on Earth accessed phosphorus. Although there was plenty of water and carbon dioxide available to work with billions of years ago, phosphorus was wrapped up in insoluble, unreactive rocks. In other words, the phosphorus was basically locked away for good.
How did organisms get access to this essential element? The prevailing theory has been that meteorites delivered phosphorus to Earth in the form of a mineral called schreibersite—which can dissolve in water, making it readily available for life forms to use. The big problem with this idea is that when life began over 3.5 to 4.5 billion years ago, meteorite impacts were declining exponentially. The planet needed a lot of phosphorus-containing schreibersite to sustain life. And meteorite impacts would also have been destructive enough to, well, kill off nascent life prematurely (see: the dinosaurs) or vaporize most of the schreibersite being delivered.
Hess and his colleagues believe they have found the solution. Schreibersite is also found in glass materials called fulgurites, which are formed when lighting hits Earth. When fulgurite forms, it incorporates phosphorus from terrestrial rocks. And it’s soluble in water.
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