Lightning strikes may have helped spark life on Earth

Scott Sutherland
·4 min read
Lightning strikes may have helped spark life on Earth
Lightning strikes may have helped spark life on Earth
Lightning strikes may have helped spark life on Earth

For life to develop on Earth billions of years ago, some very basic chemical building blocks were required. A new study reveals that billions upon billions of lightning strikes during Earth's early years may have been the necessary spark to unlock one of the most essential — phosphorus.

When we think of the elements needed for life, a few likely spring immediately to mind. In science class, we learned 'CHON', an acronym for carbon, hydrogen, oxygen, and nitrogen. These four elements are the most abundant in living things, and they link together to provide some of the basic structures for life to develop. A more accurate acronym, CHNOPS, adds the final two vital components — sulphur, which is critical for biochemical reactions to take place, and phosphorus, which is a crucial component in DNA and RNA, and is essential for living cells to produce the energy they need.

CHNOPS-elemental-building-blocks-life-Silver-Spoon-Sokpop-Wikimedia
CHNOPS-elemental-building-blocks-life-Silver-Spoon-Sokpop-Wikimedia

The elemental building blocks of life. Credit: Silver Spoon Sokpop/Wikimedia CC-by-3.0

All of these elements were in great abundance on Earth when the chemical building blocks of life would have been coming together for the first time. One — phosphorus — was generally not in a readily usable form, though. To be useful for life, phosphorus must be in a soluble form. That is, it must be able to dissolve in water. On early Earth, most phosphorus was instead locked up inside insoluble minerals.

According to a new study published in the journal Nature Communications on Tuesday, it may have been lightning strikes that freed up enough phosphorus for life to develop.

Yale University graduate student Benjamin Hess, as well as Sandra Piazolo and Jason Harvey from the University of Leeds, were looking into this problem of available phosphorus and trying to answer an important question.

They identified the best source of water-soluble phosphorus on early-Earth as a mineral named schreibersite. This mineral, mainly composed of iron, nickel, and phosphorus, has been found in meteorites. As a result, previous studies have suggested that meteorites provided the phosphorus needed for the development of life. There were many meteorite strikes in the first billion years or so of Earth's history. However, the number of meteorite strikes declined significantly over time. So, the question became: was there a more consistent source that would have continued to provide phosphorus long after the meteorite strikes quieted down?

Lightning stettler alberta UGC Jeff Adams
Lightning stettler alberta UGC Jeff Adams

This lightning strike was captured from Stettler, Alberta, and uploaded to our UGC gallery. Credit: Jeff Adams

According to the research of Hess, Piazolo, and Harvey, lightning strikes could have been this source.

When lightning strikes the ground, the intense heat of the discharge forms a mass of soil fused together into glass, known as a fulgurite. Fulgurites contain the same schreibersite minerals found in meteorites.

Fulgurite-Analysis-Phosphorus-Life-Yale-UChicago
Fulgurite-Analysis-Phosphorus-Life-Yale-UChicago

The fulgurite examined for this study. Inset, top right: a slice of the fulgurite (from the boxed area) is analyzed using Raman spectroscopy at the University of Chicago. Credit: Benjamin Hess/Yale University

To find out how much phosphorus fulgurites could have provided, the researchers constructed a computer model of Earth's environment in the first billion years after the planet formed. From that model, they determined that anywhere from 1 to 5 billion lightning flashes would have been generated every year. Of those, between 100 million and 1 billion would have been cloud-to-ground strikes.

Over a billion years, that's up to one quintillion (1,000,000,000,000,000,000) fulgurite-producing lightning strikes, all around the planet.

lightning-during-nighttime-1118869
lightning-during-nighttime-1118869

Credit: Johannes Plenio/Pexels

As for how much useful phosphorus that would produce, the researchers wrote: "an idealized tropical volcanic island setting could easily generate tens to a few hundred grams of reduced [phosphorus] (P) per km² per year. As it would take time for the phosphorus to weather out of the fulgurites, the amount of reduced P would build up over long timescales. This would lead to a relatively continuous source of phosphate weathering out of fulgurites in terrestrial environments."

"This work helps us understand how life may have formed on Earth and how it could still be forming on other, Earth-like planets," Hess told Yale News. "It makes lightning strikes a significant pathway toward the origin of life."