Strange circular structure discovered via Google Maps

While browsing Google Maps to plan a camping trip in Côte-Nord, Quebec, Joel Lapointe stumbled upon a strange structure that may have been the site of an ancient asteroid crash. IFL Science The structure is spherical, about 15 kilometers long, and surrounds Lake Marsal. Lapointe contacted geophysicist Pierre Rochette of the Center for Research in Environmental Geology (CEREGE) in France to investigate.

As a result, the team determined that an ancient asteroid impact event may have created the structure. “The terrain suggests that an impact event is highly likely,” Rochette said.

Rochette and his colleagues took a closer look and believe that the small mountain ring surrounding the lake may have been misclassified in the past. “This structure, previously thought to be a volcanic tube called Marsal breccia, is located in an area devoid of magmatic activity following the Grenville event. In fact, it is more similar to the molten rock at the bottom of a crater, much like the Mistastin and Janisjarvi craters,” the team wrote.

The area showed no signs of gravity anomalies—gravity that is stronger or weaker than would be expected based on the estimated mass of the area (for example, due to denser or lighter rocks). However, the team believes the data is not detailed enough to detect anomalies smaller than 10–15 km in diameter, so further field research is needed.

When they examined samples from the strange formation around Lake Marsal, they found silicates, large amounts of magnetite, sulfides, and zircon, all potential signs of impact melt. Based on the level of erosion, they estimated that the impact may have occurred between 450 and 38 million years ago.

“Based on the preliminary evidence available, Marsal Lake appears to be a serious candidate for the 11th confirmed impact structure in Quebec. The origin of the impact can be confirmed either through existing samples or through a more thorough exploration in the future,” the team wrote. They hope to visit the site soon to find more evidence of the asteroid impact event.