In the early summer of 1908, a massive explosion flattened more than 800 miles of forest in the remote Siberian region of Tunguska. The explosion registered on seismic stations across Eurasia, and would have measured approximately 5.0 on the Richter scale (not developed until 1935) and produced enough of a disturbance in the atmospheric pressure to be detected on barographs in Great Britain. Had the explosion occurred 4 hours and 47 minutes later, it would have wiped out St. Petersburg, due to the rotation of the Earth.

The first recorded expedition to the site of the Tunguska Event didn’t occur until 1921, and found no evidence to indicate the exact cause of the explosion. Researchers generally believe that a meteor impact caused the explosion, but no impact crater or fragments had ever been found. Other researchers believe a small comet might have been the cause of the Tunguska Event, citing glowing skies observed across Europe for several evenings post-impact, thought to be caused by dust that had been dispersed across the upper atmosphere.

Italian researchers now think they may have found the impact crater, the 164-foot-deep Lake Cheko, located just 5 miles northwest of the Tunguska Event’s ground zero. "When we looked at the bottom of the lake, we measured seismic waves reflecting off of something," said Giuseppe Longo, a physicist at the University of Bologna in Italy. "Nobody has found this before. We can only explain that and the shape of the lake as a low-velocity impact crater."

Longo also said, "To really find out if this is an impact crater, we need a core sample 10 meters into the bottom" to be able to investigate a spot where the "reflecting" anomaly was detected with seismic instruments. This could be where the ground was compacted by an impact or where part of the meteorite itself lays. The object, if found, could be more than 30 feet in diameter and weigh almost 1,700 tons.

Longo’s team plans to return to Lake Cheko next summer to further investigate the possible crater, close to the 100th anniversary of the Tunguska Event. "This is important work because we can make better conclusions about how cosmic bodies impact the Earth, and what they’re made of," Longo said. "And it could help us find ways to protect our planet from future impacts of this kind."