Lightning strikes occurring over a billion years may have provided sparks of life for the early Earth, according to researchers at Yale University.
A new study suggests that, over time, these bolts could have unlocked the phosphorus necessary for the creation of biomolecules that would form the basis of life on the planet.
Though phosphorus is necessary for the formation of life, it was not easily accessible on the early Earth as it was locked tightly inside insoluble minerals on the planet’s surface.
Scientists have long wondered how Earth’s phosphorus got into a usable form to help create DNA, RNA, and other biomolecules needed for life.
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Researchers first looked at meteorites, with the idea that they contain the phosphorus mineral schreibersite – which is soluble in water – and crashed on Earth’s surface with enough frequency to create the conditions necessary for biological life.
However, this theory has one major drawback – during the period when life is thought to have begun, anywhere from 3.5 to 4.5 billion years ago, the number of meteorites hitting Earth is known to have plummeted.
However, there is another possibility. Schreibersite can also be found in certain glasses called fulgurites that form when lightning strikes the ground.
This glass contains some of the phosphorus from surface rock, but in soluble form.
Using sophisticated computer modelling techniques, Benjamin Hess, a graduate student in Yale’s Department of Earth and Planetary Sciences and collaborators Prof Sandra Piazolo and Dr Jason Harvey from the University of Leeds estimated that early Earth saw between one to five billion lightning flashes every year. In modern times there are around 560 million flashes per year.
Of those early flashes, anywhere from 100 million to one billion would have struck the ground annually.
Over the one-billion-year period un question this would make up to one quintillion strikes, that’s one followed by 30 zeroes – enough to produce a substantial amount of useable phosphorus.
Also, the annual number of lightning strikes would have remained constant, unlike the number of meteorite collisions, and would have been most prevalent on land masses in tropical regions, providing more concentrated areas of usable phosphorus, the researchers say.
“This work helps us understand how life may have formed on Earth and how it could still be forming on other, Earth-like planets,” said Hess.
Reader Q&A: Could we farm thunderstorms for power?
Asked by: John Awbery, Reading
Sure, it’s tempting to imagine harnessing the electrical energy unleashed during a thunderstorm. After all, the average lightning bolt contains an estimated five billion joules. However, capturing and using this energy poses a raft of challenges.
The first conundrum: knowing where lightning will strike. Although lightning occurs roughly 100 times a second around the globe, these flashes are erratic and unpredictable, with only a small proportion reaching the ground.
The next challenge would be to convert the energy into a usable form. Objects struck by lightning can be heated to over 20,000°C, and the potential difference generated is around a hundred million volts. Creating equipment that could safely withstand these extreme conditions would be difficult. Any energy captured would then need to be used immediately or stored, and converting it to the low voltage, alternating current that powers our homes is extremely difficult.
Finally, the amount of energy that you could harvest from lightning may simply not justify the effort. The five billion joules in one lightning bolt amounts to about 1,400kWh – enough to power an average UK home for about four months. In reality, however, a significant proportion of this energy is dissipated into the atmosphere as heat.
All this might explain why the last organisation known to have considered the idea, a US company called Alternate Energy Holdings, gave up in 2007, declaring, “Quite frankly, we just couldn’t make it work.”
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