Tectonically-driven oxidant production in the hot biosphere.

Genomic reconstructions of the common ancestor to all life have identified genes involved in HO and O cycling. Commonly dismissed as an artefact of lateral gene transfer after oxygenic photosynthesis evolved, an alternative is a geological source of HO and O on the early Earth. Here, we show that under oxygen-free conditions high concentrations of HO can be released from defects on crushed silicate rocks when water is added and heated to temperatures close to boiling point, but little is released at temperatures <80 °C.