The Rise of Atmospheric Oxygen

Abstract
When did atmospheric oxygen rise to near present concentrations? And what led to this rise? As Kasting explains in his Perspective, recent results have provided stronger-than-ever evidence that the switch from an anoxic to an oxic atmosphere occurred around 2300 millions years ago, but researchers remain divided over the mechanism. Catling et al. resurrect a previously proposed mechanism involving hydrogen escape to space, with a couple of new twists. Whether their mechanism is viable depends on the oxidation state of the continental and oceanic crust at this crucial time of Earth's evolution.