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- An Italian expedition has begun the most detailed on-site
survey yet of the aftermath of the most powerful and devastating explosion
on Earth this century.
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- The scientist are braving heat, humidity and swarms of
biting insects in Tunguska, a remote part of central Siberia. Here, in
1908, a huge explosion caused widespread destruction but no-one yet knows
whether the culprit was a comet or a meteorite.
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- The force of the explosion was equivalent to hundreds
of Hiroshima-scale bombs and felled perhaps a hundred million trees . Strangely
no impact crater was formed, possibly because the object exploded in mid-air.
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- Middle of nowhere
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- Since then there have been only a few expeditions to
Tunguska of which the current one is the most sophisticated.
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- The team, from the University of Bologna in Italy, reached
Tunguska about ten days ago after days of aircraft and helicopter flights
from Moscow.
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- Progress reports and photographs are sent to the outside
world via the Internet which they access via satellite.
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- The scientists established a base camp on a tongue of
land protruding into a lake, as this is easier to defend from wild bears.
They next began exploring Lake Ceko, the largest body of water near to
the explosion site.
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- They intend to drill into the sediments on the bed of
the lake and hopefully collect samples of the object that exploded in 1908.
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- Trailing sonar sounders and other sensors behind a catamaran
they mapped the lake bed showing that Lake Ceko is a funnel-shaped lake
with a depth between 54 and 56 metres.
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- Penetrating radar measurements mapped some of the sediments
in the top 100 metres of the lake bed, much of which is covered with felled
trees. Fortunately they have identified several regions of clear bottom
in which to drill.
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- An automated submarine TV camera has shown vegetation
strewn on the lake bed to a great depth.
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- Siberian summer
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- Conditions in central Siberia are difficult. Mid-summer
temperatures can reach 36 degrees Celsius. The researchers say there are
fewer mosquitoes than during the previous expedition in 1991, but many
more horse-flies.
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- One of the main goals of the expedition is to make measurements
at the point on the ground that was directly under the explosion. Reaching
that spot involved a 12-kilometre trek through marshes and dense forests.
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- Samples were taken from the ground and from the bark
of living trees, as well as trees killed during the explosion. It is hoped
that material from the exploded comet may be recovered.
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- The expedition continues.
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