Crater Could Solve 1908 Tunguska Meteor Mystery
Dave Mosher Staff Writer
SPACE.com
1 hour, 39 minutes ago

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.

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." Source

The lake is reportedely some 5 miles from the impact site. Something doesn't seem right with that. On top of that, an estimated object 30 feet in diameter and 1,700 tons....when it apparently vaporized over the epicenter. Something not right about that. How many intact meteors bury themselves in the ground like that? Meteor crater in Arizona doesn't have a meteor inside it.

Very interesting. Good subject for a news thread.

Looks like we will have to wait till next summer to see if he is right about the meteorite or not.

I'm a fan of the comet theory myself. I saw a discovery channel show where they duplicated the exact effect on the trees using a scale model and an explosive charge to simulate the comet exploding. That was real proof to me.

Exactly...it exploded. So why would it be five miles away, buried in some lake. Doesn't make sense to me.

It only exploded until someone comes along with better evidence and a greater arguement for another idea.

Okay, but what they don't say is if this lake was around BEFORE the event happened. They just never mention that. That question alone would save a lot of time and money. They're just saying it's shaped funny and has chaotic sediment in it and that there are other examples of the same type of craters being lakes. But, if the meteor exploded in the atmosphere, there wouldn't be an impact crater. And why is it five miles away??? We've all seen photos of the fallen trees radiating outward so shouldn't this lake then be in the center of all these trees?? I don't think this Lake Cheko is it peoples

I thought it exploded.....thereby causing all the destruction and fallen trees.


So if it didn't explode, how was all that damage caused?

I just found this little article. Go to the link to see a picture of the lake and read the entire article......

http://www.signs-of-the-times.org/articles...r+Been+Found%3F


Gasperini's team suspects that Lake Cheko, located some 5 miles north-northwest of the blast's suspected epicenter was gouged out when the impactor struck and later filled with water. The region is remote, and it's unclear from old maps whether the lake existed before 1908.


Cheko, a small lake located 8 km from the alleged epicentre of the 1908 Tunguska Event, has an unusual funnel-like bottom morphology, with 50 m maximum water-depth near the center and a 0.16 depth-to-diameter ratio. This morphology is different from that of subarctic Siberian thermokarst lakes, and is also hard to be accounted for other 'normal' Earth-surface tectonic or erosion/deposition processes, but is compatible with the impact of a cosmic body. Based on diameter, depth and morphology of the lake crater, and assuming that the impacting object was an asteroid, a mass of 1.5 × 106 kg (10 m diameter) was estimated for the projectile. However, this estimate is probably too large, because the crater was enlarged by permafrost melting and release of H2O, CH4 and other volatiles induced by the impact into a soggy ground. The projectile that formed Lake Cheko might have been a fragment of the main body that exploded in the atmosphere 5 - 10 km above ground. A prominent reflector observed in seismic reflection profiles 10 m below the bottom at the center of the lake indicates a sharp density/velocity contrast, compatible with either the presence of a fragment of the body, or of material compacted by the impact. Drilling could solve this dilemma.

Now that makes a little bit of sense.......a little. But then there would have been two epicenters...right? Were all the trees felled around the lake?

Good questions. I have no idea. I won't be convinced until they come up with some more info. But, we'll see.

What I understand is that it exploded creating a fireball. Hence scorched earth and flattened trees but no crater.

The lake is supposed to be made from a chunk of the object that broke off. They solved this mystery ages ago.

Yeah, that sounds likely. Objects like this, be they comets or asteroids, aren't likely to explode so completely that they're essentially vaporized. I would certainly expect some large fragments to be created.

Actually according to one theory the Tanguska incident was a colision between two flying objects, so maybe one ended up in the lake the other exploded. Maybe well find some ALiens.

The force of the object flattened the trees in one area while the object landed in another. That is acceptable considering the rotation of the earth and the forward momentum of the object. When a jet travels faster than sound, you see it before you hear it because it is not moving faster than the speed of light. The gravity of the earth pulled the force down before the object or the object was travelling faster than the force. That's my thought.

Here is the best site you will ever find on Tunguska:

http://www.geocities.com/CapeCanaveral/***...3240/index.html

And here is an interesting site with witness accounts

http://www.vurdalak.com/tunguska/witness/witnesses.htm

There's no evidence that it was. In the paper, the authors write

Previous information on Lake Cheko was limited to few soundings and sediment samples collected in 1960 (Koshelev, 1963). However, as the region is remote and uninhabited, there is no reliable evidence even on whether or not the lake existed before 1908. In fact, the presence of the lake was not reported in maps drafted before 1928 and is not mentioned by eyewitness testimonies Vasilyev et al., 1981).