Lightning was much less common in Earth's early atmosphere

In a new study, scientists note that the composition of the early Earth made it difficult for lightning to form, which could

increase the time required for the formation and accumulation of prebiotic molecules important for life.

The researchers noted that the electrons behavedifferently in an atmosphere consisting of methane and ammonia, and in an atmosphere consisting mainly of carbon dioxide and molecular nitrogen. It is logical to assume that lightning discharges will also behave differently, which may affect the likelihood of the formation of prebiotic molecules on the early Earth. However, few people have modeled how lightning discharges change under different atmospheric conditions.

To see how often electrons and moleculesgases could collide in two versions of the early Earth's atmosphere, the researchers modeled the likelihood of a discharge - this is the first stage in a lightning strike. They found that in an atmosphere composed of carbon dioxide and nitrogen, this is much more difficult to achieve.

“In an atmosphere rich in nitrogen and carbon, forthe occurrence of a discharge requires stronger electric fields,”  noted Christophe Kähn, a scientist at the National Space Institute at the Technical University of Denmark who led the study.

Models have shown that in an atmosphere of carbon dioxidegas and nitrogen, the discharge requires about 28% stronger electric field, since gas molecules and electrons are less likely to collide and accumulate electrical charges. Scaling across space and time suggests that there were fewer lightning strikes early in Earth's history, making prebiotic molecules less likely to form.

The study simulated the early stages of strokelightning, so Ken and his colleagues think the next step is to simulate lightning strikes and combine that with atmospheric chemistry models. Taken together, these studies may provide a more complete picture of how lightning could be related to prebiotic molecules.

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