SPACE.COM - Earth is the only home we know, but it was not always one we could live in.
The oxygen we depend on with every breath was essentially absent when Earth formed about 4.5 billion years ago. It wasn't until about 2.4 billion years ago, when our planet was nearly half its present age, that the gas became a lasting feature of its atmosphere in a transformation known as the Great Oxidation Event. For scientists, the harder question has been how oxygen stayed abundant for millions of years afterward — long enough, as ancient rocks suggest, to set the stage for the emergence of increasingly complex life. The answer may lie in the chemistry of ancient seas, according to a new study.
The research, led by Lewis Alcott, a biogeochemist at the University of Bristol in the U.K., describes a self-sustaining cycle in which phosphorus — a fundamental building block of all known life — was recycled in the oceans, helping maintain elevated oxygen levels after they first rose.
"Living things cannot grow or function properly without phosphorus," study co-author Andrey Bekker, a professor of geology at the University of California, Riverside, said in a statement.