Without oxygen, the world as we know it wouldn’t exist. And yet scientists still don’t know why, 2.4 billion years ago, oxygen levels slowly rose to what they are now.
However, thanks to unique conditions in deep sinkholes in Lake Huron, they may be closer to finding out. Scientists are currently conducting dives in Lake Huron’s sinkholes to monitor the extremely rare organisms that can be found there: microbial mats. These mats of purple microbes, or cyanobacteria, exist only in a few places on earth, in deep lakes where the water is salty and oxygen-free.
“These microbial mats, we think, are representative of the types of organisms that would have lived billions of years ago and played a really important role in Earth’s oxygenation,” Gregory Dick, a University of Michigan research scientist, told NPR.
Scientists rarely get access to these organisms, as they usually only exist in “remote and extreme” environments, Dick says. “Places like ice-covered lakes in Antarctica, hot springs in certain regions. But this one is right here in our backyard.”
Part of the mystery around the mats is why they started producing oxygen at all. They often produce sulfur instead, and scientists are trying to determine why, those billions of years ago, they switched from sulfur to oxygen. So scientists are monitoring Lake Huron’s mats with microsensors and camera snapshots to track their production of these elements.
As Gregory Dick notes, determining how the microbial mats work not only will help scientists understand how Earth created the conditions for life, but also whether it might be happening elsewhere: “What about life on other planets? How common is this process? . . . We’re understanding our own planet’s history and understanding how it could happen on other planets as well.”