The Tunguska Mystery–100 Years Later

Finding a piece of the elusive cosmic body that devastated a Siberian forest a century ago could help save Earth in the centuries to come

By Luca Gasperini, Enrico Bonatti and Giuseppe Longo

Giant fireball in the sky was the first indication that an unknown celestial object had exploded over Siberia. In this artist’s conception, Semen Semenov, who witnessed the blast at a distant trading post, starts to feel the heat.

James Porto

Editor’s Note: This story was originally printed in the June 2008 issue of Scientific American.

June 30, 1908, 7:14 a.m., central Siberia—Semen Semenov, a local farmer, saw “the sky split in two. Fire appeared high and wide over the forest…. From … where the fire was, came strong heat…. Then the sky shut closed, and a strong thump sounded, and I was thrown a few yards…. After that such noise came, as if . . . cannons were firing, the earth shook …”

Such is the harrowing testimony of one of the closest eyewitnesses to what scientists call the Tunguska event, the largest impact of a cosmic body to occur on the earth during modern human history. Semenov experienced a raging conflagration some 65 kilometers (40 miles) from ground zero, but the effects of the blast rippled out far into northern Europe and Central Asia as well. Some people saw massive, silvery clouds and brilliant, colored sunsets on the horizon, whereas others witnessed luminescent skies at night—Londoners, for instance, could plainly read newsprint at midnight without artificial lights. Geophysical observatories placed the source of the anomalous seismic and pressure waves they had recorded in a remote section of Siberia. The epicenter lay close to the river Podkamennaya Tunguska, an uninhabited area of swampy taiga forest that stays frozen for eight or nine months of the year.

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