Phosphorus is a key element in organic compounds, including the backbones of DNA and its cousin, RNA. But where did the phosphorus used in life's earliest chemical reactions come from? Scientists have proposed that meteorites could have a key source of reactive phosphorus, but a recent study illuminates the role lightning may have played in kick-starting life on prebiotic Earth.

When schreibersite, a mineral containing iron, nickel, and phosphorus, gets hydrated, it becomes capable of making organic molecules. Schreibersite has been a known source of this form of reactive phosphorus but until now, non-meteorite sources of schreibersite were thought to be extremely rare. Such sources include special forms of glass produced by lightning strikes, called fulgurites. Fulgurites can form when lightning strikes the ground and the extreme heat changes the material impacted by the strike. 

In a new study published in Nature Communications, planetary scientists investigated minerals near a lightning strike site in Illinois. The researchers, from Yale University and the University of Leeds, found that a fulgurite produced in clay-rich soil contained a large amount of schreibersite. This finding raised the possibility that lightning strikes may have played an important role in creating the reactive phosphorus needed for life on Earth. 

The researchers used the fulgurite from Illinois and previous reports of schreibersite in fulgurites to estimate the amount of reactive phosphorus produced from each lightning strike. They combined this information with a calculated annual lightning strike rate to estimate how much reactive phosphorus would have formed from lightning strikes during the Hadean and Archean eons. 

The researchers estimated between 10 and 1000 kilograms of phosphide, and between 100 and 10,000 kilograms of other reactive forms of phosphorus (phosphite and hypophosphite) would have formed annually due to lightning strikes during these time periods. Their estimates rely on the current models of early Earth characteristics.

The findings of this study indicate lightning as a potentially meaningful source of terrestrial reactive phosphorus needed for life to start on Earth, suggesting there may be more than meteorites to our origins.