Then you will want to read this book to discover how an
alien race was the proximate cause of the Tunguska Event.

In 1908 in Siberia, the Tunguska Event was the largest explosion ever recorded on Earth. It was 1,000 times more powerful than the Atomic Bomb at Hiroshima. Eighty million trees were felled, but there was not one speck of debris ever found in dozens of research expeditions over the past century. It has been officially classified as an asteroid or comet, but only because there was no other logical explanation … until now. Learn the real cause of the explosion.