Earth may have gotten its first DNA and RNA molecules from massive amounts of lightning bolts striking our planet throughout a billion years. According to a new study, the lightning strikes may have helped release phosphorus compounds that would have been needed for kick-starting life around 3.5 to 4.5 billion years ago.
When combined with other bio-essential elements, phosphorus plays a significant role in creating life. For example, phosphates – which are incredibly important components in DNA, RNA, and ATP as well as for teeth, bones, and cell membranes – contain three oxygen atoms and one phosphorus atom.
While it is believed that there was an abundance of water and carbon dioxide in our atmosphere billions of years ago, phosphorus would have been trapped in insoluble rock. It has been suggested that meteors crashing into Earth contained schreibersite which is partly made up of phosphorus and is soluble in water. The problem with that hypothesis is that an exceptionally large amount of meteors would have had to hit the planet for enough phosphorus to be released and jump-start life.
Another problem is that when life first appeared on our planet between 3.5 and 4.5 billion years ago, the amount of meteors crashing down on Earth had dropped “exponentially” because other planets and moons in our solar system would have mostly formed and there wasn’t as much space debris knocking into us.
So, this is where the lightning bolts come into play because when they strike our planet, the surface can heat up to almost 5,000 degrees Fahrenheit (2,760 degrees Celsius) which can create new minerals. The researchers analyzed a piece of rock found in Illinois that had been struck by lightning (this lightning-struck rock is called fulgurite) and they found that it contained bits of glassy minerals and even some schreibersite.
Since they were able to determine that lightning can produce schreibersite, they needed to calculate how much lightning would have had to strike Earth for enough phosphorus to be released in order for life to begin.
Around 4 billion years ago, our atmosphere would have had much more carbon dioxide which would have resulted with many more storms, so the researchers believe that there could have been as many as 1 billion to 5 billion lightning bolts per year with approximately 100 million to 1 billion of them striking the ground. In the course of a billion years, as much as a quintillion bolts (1 followed by 18 zeros) may have struck the ground which would have released a decent amount of phosphorus – as much as 250 to 25,000 pounds of it on a yearly basis (or between 113 and 11,340 kilograms).
In an interview with Live Science, Benjamin Hess, who is a graduate student at Yale University's Department of Earth and Planetary Sciences as well as the lead author of the study, explained this further, “For life to form, there just needs to be one location that has the right ingredients.” “If [250 lbs.] of phosphorus a year were concentrated in a single tropical island arc, then yes, it may well have been enough. But it's more likely that will happen if there are many such locations.” On the other hand, it could have also been a combination of meteors and lightning strikes that started life on Earth.
The study was published in the journal Nature Communications where it can be read in full.