the morning of June 30, 1908, a giant bright blue fireball blazed
finally exploding at a height of 3 to 6
miles (5 to 10 kilometers) in the sky above Tunguska, Siberia.
The effects of the explosion
were felt for more
miles (965 km) in all
directions, windows in houses
shattering, horses and people being knocked unconscious and trains
to a halt for fear of derailment. Closer, near the epicenter, trees
were bowled over, all animal life was extinguished and a
mysterious black rain fell from the skies.
Seismic waves were
recorded In Europe and America, while the dust and debris injected into
the atmosphere caused eerie effects across Europe, Russia and western
nights so bright it was possible to read indoors. Later it was found
that atmospheric shock waves had circled the Earth twice, scientists
determining that the event whatever its cause had released energy
equal to 12 megatons of TNT.
to political instability and
the isolation of the impact site an expedition to investigate the
devastated area didn’t arrive until 1927 when a Soviet mineralogist
named Leonid Kulik (who had an interest in fallen meteorites) arrived
on the scene. Standing on a ridge he surveyed the blast area and wrote:
“From our observation point no sign of forest can be seen, for
everything has been devastated and burned . . . One has an uncanny
when one sees 20 to 30 inch (50 to 75 centimeters) thick giant trees
snapped across like twigs and their tops hurled many meters away to
Owing to problems, with his superstitious guides,
another month passed before Kulik finally reached the middle of the
and found not the impact crater expected but instead a frozen swamp in
the center of which was a copse of trees, unaffected despite clearly
being at the blast's focal point. Whatever had caused the blast had
obviously occurred far above the ground and he found no trace of the
meteoric iron fragments for which he was searching.
So if the
Tunguska explosion wasn’t caused by a meteor or small asteroid, what
did cause it? There are two prevailing theories currently in vogue. One
held by UFO aficionados speculates that it was an alien spacecraft
burning up in the atmosphere, its engines erupting in an uncontrolled
nuclear detonation. The other theory, more mainstream, maintains that
it was either a fragment or the head of a small comet.
Evidence for the alien spacecraft
and a subsequent nuclear explosion seem sketchy at best. Claims that
scabs had broken out on reindeer were cited as evidence of radiation,
but in view of the fact that none of the people in the
vicinity showed any signs of sickness it can only be
surmised that the scabs were the result of burns caused by the
initial flash of heat given off by the blast.
A one percent
increase in radiocarbon in the rings of trees growing in the United
States during the period 1908 to 1909 seemed at first to corroborate
the nuclear theory but in fact fluctuations of two percent are not
uncommon and a double check on a Norwegian tree (a good deal nearer
the explosion) revealed much lower radiocarbon levels during 1909.
clues pertaining to the second theory were unearthed by Soviet
geochemist Kirill Florensky who led expeditions to the area in 1958,
1961 and 1962. Unable to find large meteoric fragments
Florensky’s expedition chose to search for microscopic particles. Their
was successful, revealing a narrow corridor of cosmic dust stretching
for 150 miles (240 kilometers) northwest of the site. The dust was
composed of magnetite (magnetic iron oxide) and droplets of heat fused
(a low density stony composition containing flecks of iron believed
to be typical of interplanetary debris found in comet tails).
Further evidence confirming the cometary nature of
the Tunguska object came from a 2010 expedition headed by researcher
Using ground penetrating radar to examine the Tunguska site's Suslov
it was created by the violent impact of an extraterrestrial body. The
crater is structured with layers of recent permafrost on top,
damaged layers below and at the very bottom fragments of the
preliminary assessment revealed it to be a large piece of
ice that had shattered on impact lending credence to the comet theory.
Estimates are that events such as the one at Tunguska occur on average once every
two thousand years.
astronomers now believe that the Tunguska object was a
fragment broken off Comet Encke.
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