For decades, scientists have been puzzled by periodic findings of ethane and propane in sediments that they've pulled from deep below the ocean floor. As far as they knew, these gases could be produced only as petroleum is—by great heat applied to ancient, buried organic matter. But sometimes, ethane and propane turn up in areas where that process seems unlikely.
A new report suggests a different source: microbes. Bacteria and archaea within underwater sediments could chew up buried organic material and spew out ethane and propane as waste products, assert Kai-Uwe Hinrichs of the University of Bremen in Germany, and his colleagues.