AP PROVIDES ACCESS TO THIS PUBLICLY DISTRIBUTED HANDOUT PHOTO PROVIDED BY NOAA THUNDER BAY NATIONAL MARINE SANCTUARY; MANDATORY CREDIT.
This June 19, 2019 photo provided by NOAA Thunder Bay National Marine Sanctuary shows purple microbial mats in the Middle Island Sinkhole in Lake Huron, Mich. Small hills and ??sfingers??? like this one in the mats are caused by gases like methane and hydrogen sulfide bubbling up beneath them. Feel like days are just getting longer? They are and it???s a good thing because we wouldn't have much to breathe if they weren???t, according to a new explanation for how Earth???s oxygen rich atmosphere may have developed because of Earth???s rotation slowing. Scientists provided evidence for this new hypothesis by lab testing gooey smelly purple bacteria from a deep sinkhole in Lake Huron. (Phil Hartmeyer/NOAA Thunder Bay National Marine Sanctuary via AP)