ABOVE: Purple microbial mats in the Middle Island sinkhole in Lake Huron. Small hills and “fingers” like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them.
PHIL HARTMEYER, NOAA THUNDER BAY, NATIONAL MARINE SANCTUARY
Billions of years ago, Earth lacked the oxygen-rich atmosphere that today sustains most life on the planet. How the air slowly became breathable remains an unanswered question, but in a study published yesterday (August 2) in Nature Geoscience, researchers are putting forth a novel hypothesis: that the gradually slowing rotation of the Earth, which led to longer days, allowed photosynthesizing cyanobacteria to pump more oxygen into the atmosphere than they had before.
“An enduring question in the Earth sciences has been how did Earth’s atmosphere get its oxygen, and what factors controlled when this oxygenation took place,” University of Michigan geomicrobiologist and study coauthor Gregory Dick says in ...
