Life started From Lightning Bolts
It’s possible that life on Earth began with a bolt of lightning.
No, the world’s first bacteria were not literally animated by a stray thunderbolt (sorry, Dr. Frankenstein). Trillions of lightning bolts over a billion years of Earth’s early history may have helped unlock essential phosphorus compounds that paved the way for life on Earth, according to a new study published Tuesday (March 16) in the journal Nature Communications.
Lead research author Benjamin Hess, a graduate student at Yale University’s Department of Earth and Planetary Sciences, told Live Science, “In our study, we demonstrate for the first time that lightning strikes were possibly a major source of reactive phosphorus on Earth around the time that life evolved [3.5 billion to 4.5 billion years ago].”
“Lightning strikes may have thus contributed to the emergence of life on Earth by supplying phosphorus.”
Life Scattered Through Sky?
How does an out-of-the-blue event contribute to the emergence of terrestrial life? It’s all about the phosphorus atoms, or more precisely, the organic materials that phosphorus atoms can produce when combined with other bio-essential elements.
Consider phosphates, which are ions made up of three oxygen atoms and one phosphorus atom and are important to all forms of life. Phosphates are major components of bones, teeth, and cell membranes, and form the backbones of DNA, RNA, and ATP (the primary source of energy for cells).
However, while there was probably plenty of water and carbon dioxide in the atmosphere to work with around 4 billion years ago, both of which are important for life’s fundamental molecules, much of the planet’s natural phosphorus was wrapped up in insoluble rock, making it difficult to mix into organic phosphates. So, how did Earth come to possess these vital compounds?
According to one hypothesis, early Earth got its phosphorus from meteorites carrying a mineral called schreibersite, which is partly made of phosphorus and soluble in water; if tonnes of schreibersite meteorites crashed into Earth over millions or billions of years, enough phosphorus could be released into a concentrated region to provide the right conditions for biological life, according to the new study.
When life appeared on Earth around 3.5 billion to 4.5 billion years ago, the rate of meteor strikes on Earth fell “exponentially,” Hess said, since most of our solar system’s planets and moons had largely taken shape. This complicates the hypothesis of interstellar phosphorus.
Hess says that there is another way to render schreibersite right here on Earth. It just takes a little bit of ground, a cloud, and a few trillion jolts of lightning.
Bolts in Billions
Lightning can heat surfaces to nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius), forming new minerals that were not previously present. Hess and his colleagues looked at a lightning-blasted clump of rock called fulgurite that was previously excavated from an Illinois site for the new research. Tiny balls of schreibersite, as well as a number of other glassy minerals, were discovered inside the rock by the team.
The team had to determine whether enough lightning might have hit early Earth to release a large amount of phosphorus-rich schreibersite into the atmosphere, now that they had preliminary proof that lightning strikes would produce phosphorus-rich schreibersite. The researchers calculated how many lightning strikes could have fallen over the planet last year using models of Earth’s early atmosphere.
Currently, approximately 560 million lightning bolts strike the Earth each year; 4 billion years ago, when Earth’s atmosphere was considerably richer in the greenhouse gas CO2 (and therefore hotter and more vulnerable to storms), the team determined that anywhere from 1 billion to 5 billion bolts struck each year. The team calculated that between 100 million and 1 billion bolts hit the ground each year (the rest discharged above the oceans).
And, according to Hess, up to a quintillion (a 1 followed by 18 zeros) lightning strikes could have reached our young earth over a billion years, each one releasing a small amount of available phosphorus. Lightning strikes alone may have provided Earth with anywhere from 250 to 25,000 pounds of phosphorus (110 to 11,000 kilogrammes) each year between 4.5 billion and 3.5 billion years ago, according to the researchers.
Phosphorous on Consideration
That’s a wide selection, with a lot of confusion about early Earth conditions baked in. However, Hess believes that even a small amount of phosphorus may have influenced the emergence of life.
“All that is needed for life to form is a single location with the right ingredients,” Hess told Live Science. “Yes, [250 lbs.] of phosphorus per year might have been enough if it was concentrated in a single tropical island arc. However, if there are several such sites, this is more likely to occur.”
The question of whether lightning hit sufficiently exposed land on early Earth to have an effect on life will never be completely resolved. However, the latest research shows that it was mathematically feasible.
According to the researchers, it’s possible that a combination of asteroid impacts and lightning strikes provided Earth with the phosphorus it required to weave the first bio-essential molecules including DNA and RNA. However, future research into early terrestrial life should avoid striking lightning in the record.