What’s it about?
Sulfur and iron atoms come in different sizes, called isotopes. The relative amounts of these isotopes can tell us a lot. In this paper, isotopes of sulfur are used to recognize active metabolism of microbes that use sulfur in their metabolic processes. These results, combined with results from isotopes of iron, provide evidence not only of the activities of life, but also show that there was some oxygen in the atmosphere at that time, enough to oxygenate shallow water but not deep water of the ocean.
Why does it matter?
There is a lot of debate about when oxygen became a common gas in the Earth’s atmosphere. It’s important to know, because it had a direct effect on when oxygen became important in the metabolism of organisms. Before the advent of oxygen metabolism, organisms used sulfur or iron for metabolism (which is evident in the isotopes of iron and sulfur left behind).
Why did I read this?
Isotopes are among our best tools to explore the origins of life on Earth. And, isotopes are my tool of choice for studying the behavior and preferences of extinct animals. So naturally, I had to read this.