How young Earth stayed warm

Abstract

Around 2.4 billion years ago, conditions on Earth changed dramatically. Oxygen levels soared, methane levels dropped, and the planet entered an ice age. Thankfully, this ice age wasn’t severe enough to prevent complex life from forming. Geochemists are still trying to figure out what happened during the Great Oxidation Event. Now, using nickel-isotope analysis, chemists have found more of the story. New kinds of rock weathering during this time could have continued to seed the oceans with metals needed by methane-producing bacteria, allowing the microbes to continue to produce the planet-warming gas (Nat. Geosci. 2019, DOI: 10.1038/s41561-019-0320-z). “We could have been a planet with primitive life forever, but something happened,” says Laura Wasylenki, a geochemist at Northern Arizona University who led the research. On ancient Earth, oxygen had no chance to accumulate because there was so much methane in the atmosphere, Wasylenki says. Methane and oxygen react to form carbon