Featuring C-DEBI researcher Jennifer Glass.
For much of its first two billion years, Earth was a very different place: oxygen was scarce, microbial life ruled, and the sun was significantly dimmer than it is today. Yet the rock record shows that vast seas covered much of the early Earth under the faint young sun.
Scientists have long debated what kept those seas from freezing. A popular theory is that potent gases such as methane – with many times more warming power than carbon dioxide – created a thicker greenhouse atmosphere than required to keep water liquid today.
In the absence of oxygen, iron built up in ancient oceans. Under the right chemical and biological processes, this iron rusted out of seawater and cycled many times through a complex loop, or “ferrous wheel.” Some microbes could “breathe” this rust in order to outcompete others, such as those that made methane. When rust was plentiful, an “iron curtain” may have suppressed methane emissions.