Life on Earth may have arisen from a quintillion lightning strikes

The exact recipe for how life got started on Earth – and whether it’s appeared on other planets too – are some of the most profound mysteries of science. Now, scientists have found that lightning strikes could have contributed a key ingredient, which suggests it could be easier than we thought to spark life on other planets.

Phosphorus is one of just six crucial elements for life as we know it, and while it’s common on modern-day Earth that may not always be the case. In the distant past any phosphorus found on Earth would have been locked away inside insoluble minerals, inaccessible for any burgeoning biomolecules that may need it.

Bioavailable forms of phosphorus are mostly produced in supernova explosions, and the generally accepted story goes that it was delivered to Earth on comets and asteroids in the form of the mineral schreibersite. But that doesn’t necessarily hold up – meteorite strikes are intermittent events, and it’s believed that their frequency actually dropped during the period life emerged.

In the new study, researchers from Yale and the University of Leeds investigated an alternative way for nature to unlock phosphorus – lightning strikes. Schreibersite has also been found in glasses called fulgurites, which are created when lightning strikes the ground and flash-melts surface rock, conveniently freeing up the phosphorus.

The team modeled the conditions of early Earth and found that it would have experienced between 100 million and a billion lightning strikes per year. That of course would produce a huge amount of bioavailable phosphorus – up to 1,000 kg (2,200 lb) of phosphide and 10,000 kg (22,000 lb) of phosphite and hypophosphite each year.

The lightning strike story helps explain a few other things that meteorites don’t, too. Lightning strikes would be more constant year to year, and tend to congregate in tropical regions, where meteorites wouldn’t have that preference. Plus, lightning is likely to be common on exoplanets.

“It makes lightning strikes a significant pathway toward the origin of life,” says Benjamin Hess, lead author of the study. “This work helps us understand how life may have formed on Earth and how it could still be forming on other, Earth-like planets.”

The research was published in the journal Nature Communications.

Source: Yale University