Early on the morning of June 30, 1908, a tremendous explosion rocked the Tunguska region of Central Siberia. Hundreds of square miles of forest were completely flattened, a huge fireball rose into the sky, and a large black cloud appeared above the region. A shock wave circled the globe twice, and strange, glowing skies ere evident throughout Europe and Asia for days after the event.



Since the event occurred, several theories relating to its origin have been presented. Some feel that the explosion was the result of a meteor impact, while others feel that a comet was responsible for the devastation. Still others feel that because of the observed trajectory of the incoming object, it may have been an extraterrestrial spacecraft of some type.

Years later, when the first research team finally reached ground zero, they observed no crater, and could not locate any meteor debris, so the meteor theory was dismissed (by most), and the comet theory became popular. A comet, composed mostly of ice and dust, would explode upon entering the earth's atmosphere, creating an airburst similar to that observed in this case. The conversion of the kinetic energy of the incoming comet to heat would result in a blast of tremendous proportions.

The question is: Why wasn't the comet seen as it approached the earth? A comet that close to the sun exhibits a glowing nucleus and extensive tail, making it easily visible to the naked eye. If the object was indeed a comet, it must have approached from a direction with a very small angular distance from the sun, rendering it invisible. Given an early morning time of impact, the comet would then have approached from the east with the tail streaming ahead of the nucleus (away from the sun) towards the west which may account for the glowing night skies seen over Europe and Western Asia after the explosion.

The proponents of the extraterrestrial spacecraft theory dispute the comet theory for several reasons. First of all, several eyewitnesses claim to have seen the object approaching from the southwest, veer towards the east, then back toward the west before exploding. Also, the object appeared to slow down just prior to the blast. The blast pattern itself appeared to be irregular, suggesting that the explosion occurred inside some type of restrictive shell. Other evidence suggests the possibility that the blast was nuclear in nature, thus accounting for the increase radioactivity levels reported in the region and accelerated plant growth in the years following the explosion.

At best, proof of the source of the Tunguska explosion is far from definitive. Unfortunately, the region is not easily accessible, and is not a pleasant environment to work in, so it is unlikely that we will ever know for sure what precisely happened. Expeditions are planned to probe some of the lakes and bogs near ground zero for meteoric evidence, but for now, speculation continues.