Lightning strikes occurring over a billion years may have provided sparks of life for the early Earth, according to new research.
A new study suggests that, over time, these bolts unlocked the phosphorus necessary for the creation of biomolecules that would be the basis of life on the planet.
Phosphorus is necessary for the formation of life but was not easily accessible on Earth billions of years ago.
For the most part, phosphorus was locked tightly inside insoluble minerals on Earth’s surface.
Scientists have wondered how Earth’s phosphorus got into a usable form to help create DNA, RNA, and other biomolecules needed for life.
Benjamin Hess, a graduate student in Yale’s Department of Earth and Planetary Sciences, said: “This work helps us understand how life may have formed on Earth and how it could still be forming on other, Earth-like planets.”
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, the drawback to this theory had to do with frequency.
During the period when life is thought to have begun, anywhere from 3.5 to 4.5 billion years ago, the frequency of meteorite collisions on Earth plummeted.
However, there was another source of the phosphorus found in schreibersite.
According to researchers, 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 results from computer modelling, Mr Hess and co-authors Sandra Piazolo and Jason Harvey from the University of Leeds estimated early Earth saw one to five billion lightning flashes every year (compared to about 560 million flashes per year today).
Of those early flashes, anywhere from 100 million to one billion would have struck the ground annually.
That would make up to 0.1 to one quintillion strikes, and a lot of usable phosphorus, after one billion years.
According to the research published in Nature Communications, the lightning strike theory has a number of other advantages, including that the annual number of lightning strikes would have remained constant, unlike the number of meteorite collisions.
Also, lightning strikes were likely to be most prevalent on land masses in tropical regions, providing more concentrated areas of usable phosphorus.
Mr Hess said: “It makes lightning strikes a significant pathway toward the origin of life.”