The powerful explosion, said to be equal to a thousand atomic bombs, that shook a 2,000-square-kilometer of forest in Tunguska, Siberia on the 30th of June, 1908 is still a mystery. It leveled the forest in a radial, circular fashion with the epicenter marked by trees which were the only ones left standing.
Theories abound about the event. The most popular and widely-accepted of these is that of a body from space, like a meteor, comet, or asteroid which exploded no more than ten kilometers above the ground in what is called an aerial burst. Now, researchers Luca Gasparini, Giuseppe Longo and colleagues from the University of Bologna are thinking that a small, shallow body of water, lake Cheko, near the epicenter of the blast could have remains of the body that caused it. At top-left is an exaggerated 3D representation of Lake Cheko and an aerial view of it.
The lake, they say, was created when part of this object hit the ground with a much lessened velocity after the parent body exploded in the air. The picture at left shows toppled trees near the center. Initial analysis of the bottom of the lake reveals a layer of mud underneath of which (10 meters) lies what may be convoluted remains of an extraterrestrial object mixed with terrestrial matter. Lake Cheko strangely does not appear in maps prior to 1928. Photos and references are from BBC news.