What drew these 1,300 perfect circles on the sea floor? We may finally know

SOURCE: NAT GEO

When hundreds of eerily perfect circles were discovered on the bottom of the Mediterranean Sea, theories abounded about what they could mean. Four years of underwater research revealed a lost world.

On a bright, hot day in mid-September 2011, Marine biologist named Christine Pergent-Martini was hunkered down inside the cabin of a small research vessel, a 97-foot-long catamaran, cruising through the Mediterranean Sea about 12 miles off the coast of Corsica. Outside the ship’s windows, the sun glinted off the dark-blue water, but Pergent-Martini ignored the waves. She was more interested in what lay beneath them.

A monitor in front of her displayed images from the vessel’s onboard sonar system, which was emitting a series of short acoustic pulses to reveal the underwater topography about 400 feet below. The ocean scientist was nearing the last day of a month-long mission: With a small crew, including her husband, oceanographer Gérard Pergent, and a graduate student from the University of Corsica Pasquale Paoli, Pergent-Martini had been mapping the seafloor in this region.

The seemingly simple goal actually targeted one of oceanography’s major blind spots.

The Mediterranean Sea covers about a million square miles, stretching from the Strait of Gibraltar in the west to Lebanon in the east. While its surface has been traversed since ancient times by everything from Greek triremes to Etruscan warships, its depths are mysterious to modern science. Much of its seafloor exists in something of a liminal zone: too shallow and close to the shore to draw interest from deep-sea mining companies but still too deep to be reachable by conventional scuba divers. Pergent-Martini and her colleagues wanted to learn more about what lived on the bottom at these depths.

At first, the day was no different from any other. As the boat moved across the water, the scientists watched a series of predictable grainy black-and-white images appear on-screen: Sand. Small rocks. More sand. It was all stuff they’d seen before. But then something truly bizarre scrolled into view.

A perfect circle, then another, then another. They were all about the same size—around 67 feet in diameter—with a distinct outline and striking symmetry. Weirder still, almost every ring had a dark spot directly in the center. They looked like fried eggs, Pergent-Martini thought, and there appeared to be several dozen of them.

The scientists looked at each other. “We had no idea what it was,” Pergent-Martini says. Her team carefully logged their location and used a remotely operated vehicle to gather images.

Still, the mystery only deepened. They captured video footage of the circles, but the view was too murky to confirm much more than the fact that this wasn’t sunken cargo.

When the researchers presented their findings at a 2013 scientific meeting, they were still in search of answers about the nature of the rings. Even a follow-up study with a submarine in 2014 didn’t answer all their questions. In time, researchers would count more than 1,300 of these circles over a nearly six-square-mile area.

After years of applying for grants to study the rings more closely, the Pergents reached a dead end. “It was very difficult to obtain money,” Pergent-Martini said. The Pergents are specialists in seagrass meadows, and this was a bit outside their focus. “We had no way to go farther.” Then, just the right person got in touch. In the world of undersea exploration, Laurent Ballesta is known for going to extremes. A photographer, marine biologist, technical diver, and National Geographic Explorer, he co-runs Andromède Océanologie, a company that leads scientific missions to document some of the world’s most inaccessible places. These undertakings often require specialized equipment and elaborate dive plans.

FULL ARTICLE, MORE PHOTOS & THE ANSWER HERE

 - AUTHOR: VERONIQUE GREENWOOD

 - SOURCE: NATIONAL GEOGRAPHIC