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Famous 1908 Impact Crater Found?

By Dave Mosher, Space.com,
Posted: 2007-06-27 08:29:41
Filed Under: Science News
Space.com


(June 26) - In late June of 1908, a fireball exploded above the remote Russian forests of Tunguska, Siberia, flattening more than 800 square miles of trees. Researchers think a meteor was responsible for the devastation, but neither its fragments nor any impact craters have been discovered.

www-th.bo.infn.it/tunguska / University of Bologna

Italian researchers believe the 164-foot-deep Lake Cheko is the site of the mysterious 1908 impact that shook Siberia.

Astronomers have been left to guess whether the object was an asteroid or a comet, and figuring out what it was would allow better modeling of potential future calamities.

Italian researchers now think they've found a smoking gun: The 164-foot-deep Lake Cheko, located just 5 miles northwest of the epicenter of destruction.

"When we looked at the bottom of the lake, we measured seismic waves reflecting off of something," said Giuseppe Longo, a physicist at the University of Bologna in Italy and co-author of the study. "Nobody has found this before. We can only explain that and the shape of the lake as a low-velocity impact crater."

Should the team turn up conclusive evidence of an asteroid or comet on a later expedition, when they obtain a deeper core sample beneath the lake, remaining mysteries surrounding the Tunguska event may be solved.

The findings are detailed in this month's online version of the journal Terra Nova.

During a 1999 expedition, Longo's team didn't plan to investigate Lake Cheko as an impact crater, but rather to look for meteoroid dust in its submerged sediments. While sonar-scanning the lake's topography, they were struck by its cone-like features.

"Expeditions in the 1960s concluded the lake was not an impact crater, but their technologies were limited," Longo said. With the advent of better sonar and computer technologies, he explained, the lake took shape.

Going a step further, Longo's team dove to the bottom and took 6-foot core samples, revealing fresh mud-like sediment on top of "chaotic deposits" beneath. Still, Longo explained the samples are inconclusive of a meteorite impact.

"To really find out if this is an impact crater," Long said, "we need a core sample 10 meters (33 feet) into the bottom" in order to investigate a spot where the team detected a "reflecting" anomaly with their seismic instruments. They think this could be where the ground was compacted by an impact or where part of the meteorite itself lays: The object, if found, could be more than 30 feet in diameter and weigh almost 1,700 tons-the weight of about 42 fully-loaded semi-trailers.

From a UFO crash to a wandering black hole, wild (and wildly unsupported) explanations for the Tunguska event have been proposed. Alan Harris, a planetary scientist at the Space Science Institute in Boulder, Colorado, said the proposal by Longo's team isn't one of them.

"I was impressed by their work and I don't think it's something you can wave off," said Harris, who was not involved in the research.

Longo and his team "are among the recognized authorities on Tunguska" in the world, Harris told SPACE.com. "It would be thrilling to dig up chunks of the meteor body, if they can manage to. It would lay the question to rest whether or not Tunguska was a comet or asteroid."

Some researchers, however, are less confident in the team's conclusions.

"We know from the entry physics that the largest and most energetic objects penetrate deepest," said David Morrison, an astronomer with NASA's Ames Research Center. That only a fragment of the main explosion reached the ground and made a relatively small crater, without creating a larger main crater, seems contradictory to Morrison.

Harris agreed that physics could work against Longo's explanation, but did note that similar events-with impact craters-have been documented all over the world.

"In 1947, the Russian Sikhote-Alin meteorite created 100 small craters. Some were 20 meters (66 feet) across," Harris said. A site in Poland also exists, he explained, where a large meteor exploded and created a series of small lakes. "If the fragment was traveling slowly enough, there's actually a good chance (Longo's team) will unearth some meteorite material," Harris said.

Longo's team plans to return to Lake Cheko next summer, close to the 100th anniversary of the Tunguska Event. "This is important work because we can make better conclusions about how cosmic bodies impact the Earth, and what they're made of," Longo said. "And it could help us find ways to protect our planet from future impacts of this kind."

(c) 1999-2007 Imaginova Corp. ALL RIGHTS RESERVED.

2007-06-26 13:28:07
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7 comments

richardsud 01:52:00 PM Aug 14 2007

BUSH DID IT. JUST ANOTHER AMERICAN CONSPIRACY. TOO MANY "TERRORISTS" HERE ON EARTH. THE TRUTH HAS BEEN POINTED OUT. - RICHARD

AmberPro 02:27:49 PM Jul 05 2007

[previous comment concludes]
...It is just an incidental mention, also at second-hand, but the repetition rules out a mistake in transmission, and the context strongly implies that Lake Cheko was a well-known waypoint among the hunters and trappers who traveled that forest road prior to the Event. (After the Event, such landmarks would have been of no use, since the area had become, to all intents and purposes, closed to traffic.)

For more detail, see the blog at http://www.myspace.com/billdesmedt

AmberPro 02:27:02 PM Jul 05 2007

[previous comment continues]
...Three mentions of the ?mouth? of the Cheko (i.e., the point at which the lake flows out into a stream) makes it pretty definite that the younger Dzhenkoul has not misremembered his hand-me-down tale. And the context makes clear that the second storehouse must have been located at the mouth of the Cheko before the Event, since the blast itself swept the structure away. Which, in turn, means the Cheko itself was there too.

Finally, we have the testimony of Vasilii Nikolaevich Dmitriev taken in 1960 by G. B. Kolobkova (VINITI, page 104/61):

The road from Strelka to Vanavara passed through Lake Cheko, From Ilimpei you could go to Strelka. There was no trading post there at that time, but the road went through. Further on toward Vanavara, the road went through [across?] Lake Cheko.

It is just an incidental mention, also at second-hand, but the repetition rules out a mistake in transmission, and the context strongly implies that Lake Cheko was a well-known

AmberPro 02:24:58 PM Jul 05 2007

[previous comment continues]
...In that place the seven rich Dzhenkoul brothers in those days pastured a reindeer herd of 600-700 head. The brothers were rich. On that day, [my] father went to meet the reindeer on the Ilimpo [river] (in the north). The herd was pastured between the Kimchu river and the Polnoty (Churgim) river. On the upper reaches of the Polnoty river there was a storehouse. There was a second storehouse at the mouth of the Cheko. There, where the first storehouse was (on the Polnoty-Churgim), there everything was burnt up. Of that storehouse there remained only ashes. The storehouse at the mouth of the Cheko was thrown over (carried away) by a whirlwind. At the headwaters of the Khushmo [river] their herd was burned, the reindeer were burnt up, only ashes remained. At the mouth of the Cheko, the reindeer lay curled up, but they didn?t burn (they had been stunned and they died).

Three mentions of the ?mouth? of the Cheko (i.e., the point at which the lake flows out in

AmberPro 02:23:52 PM Jul 05 2007

Lyuchetkan seems to be about as close to an unimpeachable witness as we?re likely to find in these annals: He lived close to the impact site (his brother, who lived even closer, had his hut blown into the air ?like a bird? from the blast and became so afraid he was struck mute for several years thereafter). As a herder and hunter, Lyuchetkan could be expected to know the surrounding area as well as anyone. And his veracity is independently attested by one N. N. Kartashov, who stated to geologist A. N. Sobolev that ?it is impossible not to believe Ilya Potapovich?s story? (VINITI, page 13/8).

But was the lake Lyuchetkan spoke of the one we?re looking for? There are two other accounts in the catalogue that strongly suggest it was.

The first, by Lavrentii Vasil?yevich Dzhenkoul, was collected in 1960. Dzhenkoul was only four years old at the time of the 1908 blast, but he recounted the stories passed down to him by his father and uncle (VINITI, page 95/56):

In that place the seven rich

AmberPro 02:23:13 PM Jul 05 2007

[previous comment continued]
...(though I?ve translated a few of the more interesting bits for the ?Vurdalak Conjecture? website ? see http://www.vurdalak.com/tunguska/witness/witnesses.htm).

So, does this document have anything at all to say about Lake Cheko? More particularly, about whether it was there before the impact or not?

Let?s start with what seems to be the earliest recorded account making mention of a lake: the report of Ilya Potapovich Popov (more commonly referred to by his Evenki name Lyuchetkan), taken in 1924 by geologist S. V. Obruchev (VINITI, p. 23/14). There we find Lyuchetkan saying, ?In that place where the stone fell, there is a pit, and from it some creeks [running] into the Chambu. There is a lake nearby, but it existed before the fall of the meteorite.?

Lyuchetkan seems to be about as close to an unimpeachable witness as we?re likely to find in these annals: He lived close to the impact site (his brother, who lived even closer, had his hut blown into the a

AmberPro 02:19:15 PM Jul 05 2007

Of course, the whole Bologna "solution" falls apart if it can be convincingly shown that Lake Cheko antedates the Tunguska Event.

On that score, it is instructive to review the catalogue of Tunguska eyewitness accounts available on the Internet at http://olkhov.narod.ru/tungwitn1.htm. (The catalogue, entitled ?Testimony of the Eyewitnesses to the Tunguska Impact,? was compiled back in 1981 for the archives of the All-Union (now All-Russian) Institute for Scientific and Technical Information (VINITI) by the grand old man of Soviet/Russian Tunguska studies Academician Nikolai Vladimirovich Vasil?ev himself. It gathers into one document both contemporary newspaper reports and the testimony of witnesses to the Event recorded by a variety of researchers from 1921 through the 1970s. The sole drawback is that, to date, the bulk of its materials are available only in Russian (though I?ve translated a few of the more interesting bits for the ?Vurdalak Conjecture? website ? see http://www.vurda

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