Lightning did not play a major role in the emergence of life on Earth, as scientists have long believed. A new study published in Nature Geoscience shows that lightning had a modest effect on the development of the first life forms.
Earth’s ancient atmosphere consisted mostly of carbon dioxide and nitrogen, making it unsuitable for generating lightning. Thunderstorms were much rarer than today. However, after the emergence of living things, they began to capture atmospheric nitrogen on their own, no longer relying on lightning strikes.
Nitrogen is one of the most important elements for life, but most of it is found on Earth in the form of the inactive molecule N2, which makes it almost inaccessible to living things. Presumably, before the emergence of nodule bacteria, the main “supplier” of nitrogen for primitive living organisms was lightning. Under their influence, atmospheric nitrogen was transformed into nitrogen oxides, nitrites and nitrates.
A team of scientists conducted experiments to find out how this happened. They used flasks filled with water and various gas mixtures, through which electrical discharges of nearly 50,000 volts were passed. This caused concentrations of nitrogen-containing compounds in the flasks to increase.
However, the isotopic composition of such compounds does not correspond to the composition of nitrogen in the oldest rocks of the Earth, which suggests a small role of lightning in providing nitrogen to the first microbial life. According to the researchers, this provides evidence that for more than three billion years living organisms have been providing themselves with available nitrogen without relying on random lightning discharges.
Most likely, lightning played its main role only at the very beginning of the development of the first living organisms, as evidenced by the composition of rocks formed about 3.8 billion years ago and found in Greenland. However, already 3.2 billion years nitrogen concentrations in rocks become too high for lightning, which means the beginning of nitrogen-fixing activity of the oldest microorganisms on our planet.
Thus, lightning is not the main catalysts of synthesis of organic substances and emergence of the first life forms on Earth. This is confirmed by new research and additional data, which suggest a modest role of lightning in this process.