Hosted by Hanneke Weitering Tunguska impact levels hundreds of miles of Siberian forest. Near the Stony Tunguska River in Siberia (now Krasnoyarsk Krai, Russia), a fireball flew across the sky, causing an explosion moments later. At the time, it was too difficult to reach this part of Siberia to study what might have happened, but in 1927 Leonid Kulik led the first research expedition to investigate. There wasn’t a meteorite crater or any fragments in the area, causing much speculation as to what might have happened. It is believed to have been caused by a comet or asteroid that exploded in the atmosphere instead of striking Earth. This caused an “air burst,” above Earth’s surface. And that's what happened, Today in Space!