In the early morning hours of June 30, 1908 a great fireball streaked across the Siberian sky and exploded
several kilometers above the surface of the earth.  Commonly called the "Tunguska Event", it was the first
giant object to impact earth in the time of civilized man.  It puzzled scientists because of its vast blast
effect that did not leave a crater.  The power of its blast, on the order of a big "city buster" H-bomb, made
trees fall outward in a radial pattern over an area of 2000 square kilometers with a small area of upright
tree trunks left at the epicenter.  This same type of blast signature was made by the air burst from
A-bombs which were dropped on Japan, ending WWII.  The flash of heat from the energy release instantly
turned much of the forest to ash.  Scientists believe the object was either a comet or stony asteroid,
however, many scientific expeditions into the blast area have proven a lack of asteroid type debris.  Most
likely the intruder object was made up of comet like material, water ice which melted or evaporated, and
left no evidence.  Humankind was lucky, hundreds of thousands would have been killed had this object
burst above a populated area.
Russian explorer Leonid A. Kulik braved the isolated swamps and
rivers of Central Asia to study the Tunguska mystery.