The importance of lightning in early life

Nitrogen is an essential element in the air. It is an essential component of large biological molecules such as proteins, DNA and RNA, and is therefore of enormous biological importance for the origin and maintenance of life.

However, the chemical element rarely occurs in nature in the form of an atom because it immediately combines to form molecular nitrogen (N2). It may also have occurred in the early Earth’s atmosphere, but cannot be organically linked.

Perform flash experiments in glass vials

The researchers therefore suspect that the N2 molecules were “split” back into highly reactive nitrogen atoms by high-energy physical processes such as lightning, and thus became bioavailable. So researchers from the University of St Andrews in Scotland, Graz IWF and Brown University in the US conducted lightning experiments.

In these experiments, glass flasks were filled with water and various gaseous mixtures to mimic the atmosphere of early Earth. The gases were flashed by electrical discharges of approximately 50,000 volts, and then changes in composition were analyzed. Particular attention was paid to the nitrogen molecules produced in the process, such as nitrogen oxides, nitrites, and nitrates.

Nitrogen oxides food for early life on Earth

The results of the experiments showed that lightning “could efficiently produce nitrogen oxides in Earth’s ancient carbon dioxide-rich atmosphere,” Patrick Barth, PhD student at IWF Graz and St. Andrews Center for Exoplanet Science and first author of the study, noted on one hand. So nitrogen oxides could be a potential source of nutrients for early life on Earth as well as on exoplanets.

However, analyzes of early terrestrial rock samples showed that the isotopic composition of nitrogen molecules did not agree with the results of lightning experiments. According to the authors, this indicates that lightning was not the main source of nitrogen for the first forms of life on Earth. Instead, the study will provide further evidence that microorganisms must be responsible for providing nitrogen.

However, there are rock samples from Greenland’s Isua Greenstone Belt whose isotopic composition can be partially explained by lightning. This indicates that lightning may have supported at least the first forms of life on Earth.