The isotopes of nitrogen and carbon measured in several Australian shale 2.5 billion years ago can inform us of the aerobic cycle of nitrogen. The nitrogen cycle maintains the balance between the atmosphere and living beings. There are living things that cannot take nitrogen directly from the atmosphere.

According to Washington University researcher Jessica Garvin and her team, the aerobic cycle of nitrogen may develop before oxygen begins to accumulate in the atmosphere. In fact, they have seen that certain microorganisms evolved at that time were able to produce nitrates and nitrites by adding oxygen to ammonia, compounds that can be used by living beings. Previously, other microorganisms convert nitrogen into ammonia.

Image: Image: Roger Buick, University of Washington