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Crater From 1908 Tunguska Blast Found
Posted by
kdawson
on Thu Nov 08, 2007 09:16 AM
from the fire-came-by dept.
from the fire-came-by dept.
MaineCoasts writes "A team of scientists from the Marine Science Institute in Bologna claims to have found the crater left by the aerial blast of a comet or asteroid in 1908 in the Tunguska region of Siberia. The blast flattened 770 square miles (2,000 square kilometers) of forest, but to date no remains or crater have been found. This has left open the question of what kind of object made the impact. The team believes that, contrary to previous studies, nearby Lake Cheko is only one century old and 'If the body was an asteroid, a surviving fragment may be buried beneath the lake. If it was a comet, its chemical signature should be found in the deepest layers of sediments.' The team's findings are based on a 1999 expedition to Tunguska and appeared in the August issue of the journal Terra Nova."
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Submission: Crater From 1908 Tunguska Blast Found by Anonymous Coward
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Technology: Tunguska Blast Was a Small Asteroid 277 comments
malachiorion writes "The Tunguska event, an explosion on June 30, 1908, cleared an 800-sq.-mi. swath of Siberian forest. Was it a UFO crash? An alien weapons test? Now, Sandia National Laboratories has released its own explanation for the Tunguska event. Using supercomputers to create a 3D simulation of the explosion, the Department of Energy-funded nuke lab has determined that Tunguska was, indeed, the explosion of a relatively small asteroid. The simulation videos are well worth checking out — they show a fireball slamming into the earth from the asteroid's air burst. The researchers caution that we should be keeping watch for many more small, potentially earth-impacting asteroids than we are currently tracking."
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Details Emerging On Tunguska Impact Crater 164 comments
#space_on_irc.freenode.net (Dusty) writes "Lake Cheko in Siberia has been noted as the probable crater of the 1908 Siberian Tunguska event. This news was discussed here in December, but details on the crater were scant. Now a new paper written by Luca Gasperini, Enrico Bonatti, and Giuseppe Longo (the same team in Bologna, Italy that made news in December) has a horde of new details on the supposed crater. The team visited Lake Cheko complete with their own catamaran and completed ground-penetrating radar maps, side-scanning sonar images, aerial images, and some sample collection of Lake Cheko. Intriguingly, they also imaged an object under the sediment that may be a fragment of the impacting body. Their paper (PDF) includes a lot more details including images, side-scanning sonar image, a 3-D view of the lake, a morphobathymetric map. It's an interesting read, these dudes are good. They plan to return this summer and drill the core if weather permits, hopefully answering the question once and for all." The same team also has a more discursive article in the current Scientific American that includes some detail on the working conditions in the Siberian summer. Think: mosquitos.
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I've always wondered (Score:5, Insightful)
At the time I wondered, after seeing all those flattened trees, how they failed to find the crater. Wouldn't it just be a case of going to several spots, drawing a parallel line to the flattened trees, then looking on a map for the point where the lines intersect? Presumably all the trees fell "away" from the blast area.
Re:I've always wondered (Score:5, Interesting)
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Re:I've always wondered (Score:5, Informative)
Also, my post on this [slashdot.org] has a link to a PDF with a sketch of the breaking apart and trajectories.
Also, remember how long ago this happened. There was an expedition there but they didn't have the technology we did. I'm not sure if the tree patterns would help you 100 years later.
Parent
Re:I've always wondered (Score:5, Interesting)
Yes. Something that is easy for us to forget is that they didn't have roads, or even much in the way of all terrain vehicles, much less helicopters or satellites when this occurred. Not to mention, it was largely ignored until after the revolution and WWI were both finished up with. The first aerial photographs taken of the site were taken 30 years later and still clearly showed the fall pattern, but no crater was visible.
It's easy to look at the pictures and think you can simply follow the trees all the way to the center. Way easier said than done. First of all, the site is pretty much in the middle of nowhere. There's just a few scattered villages, no doubt with abysmal roads between each and almost nothing traversable with wheels leading anywhere else. They would have walked or ridden pack animals for the entire survey.
It's also a huge area. 80 million trees were felled over 830 square miles. Hunters (I've done my share) and loggers are probably familiar with trying to walk through such an area. The trees may look all neatly arrayed in a photograph, as if you could step easily from one to the next or walk between them like a trail, but the truth is far different. Without the perspective benefit from being atop a hill, the fall pattern is more difficult to discern. The branches will lie tangled, blocking the path at frequent intervals. The trunks will be random distances apart, some managing to overlap nearby trunks. They often sit several feet above the ground, making it easy to fall and twist an ankle or knee, and exhausting to climb over again and again and again. Vegetation will have sprouted up in the 19 years between the fall and Kulik's arrival, leaving a tangled mess of shrubs and briers that sometimes appear deceptively solid from above and forboding from ground level. A mile per hour is a decent speed walking through such an area with several days worth of supplies on your back.
But Kulik actually did push through to the center, and he found several trees standing upright, stripped of their branches, consistent with an airburst from above. He also found a bog he was convinced was a crater, but when he drained it there were old tree stumps at the bottom. For an impact to have formed the bog the blast would have shattered the old trees and tossed the remains out of the muddy crater.
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Airburst (Score:5, Informative)
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Re:Airburst (Score:4, Informative)
I think you may have a misconception as to why an airburst occurs. A meteor (or comet) enters the atmosphere and is decelerated by interacting with the air. To first order the rate of deceleration (and therefore the stress on the meteor) is related to the ratio of the surface area of the object to its mass. If the deceleration stress exceeds the tensile strength of the material it will fragment. If you break an object into multiple pieces, you've increased the surface area but left the total mass the same. The net effect that fragmenting increases the stress and results in more fragmentation and more rapid deceleration. Once fragmentation starts it doesn't like to stop. It progresses very rapidly and all of the kinetic energy gets turned into heat in a few microseconds.
Another way of thinking about it is that it would be hard to get solid pieces surviving after a 15 megaton airburst. Pick your favorite 60 meter diameter piece of rock. Put a 15 Mton H-bomb on it and set if off. Tell me home much of your rock is left.
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Re:Airburst (Score:5, Interesting)
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Re:I've always wondered (Score:5, Insightful)
Right now we'd simply take some pictures with a satelite, and fly some helicopters to the impact spot. Back then they would've had to mount an expedition on foot. And that was simply not feasible.
By the time it became possible to reach the impact site relatively easy, nature had already taken its course and finding the impact spot became impossible/very hard.
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Re:I've always wondered (Score:5, Funny)
Apollo 11 mission...
\ |
- O -
/ | \
It reminds me of something...
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What kills me is that a 1999 expidition is just now being published? WTF have they been doing all these years? How slow are they typing? Did they get a monk to transcribe it for them?
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Re:I've always wondered (Score:4, Interesting)
From what I know of the event, and as is stated in the summary, it was an aerial blast; i.e. the asteroid/comet/alien-spaceship exploded before impact. The "crater" where the remains of the $object should be found would not be directly under that explosion, as the $object would have some unknown velocity at some unknown angle.
While the method you propose makes sense, all it really tells you is where the explosion occured, not where the remains can be found.
Aikon-
Parent
Oblig Ghostbusters (Score:4, Funny)
Louis: Who are you guys?
Dr Ray Stantz: We're the Ghostbusters.
Louis: Who does your taxes?
Dr Ray Stantz: You know, Mr. Tully, you are a most fortunate individual.
Louis: I know!
Dr Ray Stantz: You have been a participant in the biggest interdimensional cross rip since the Tunguska blast of 1909!
Louis: Felt great.
Dr. Egon Spengler: We'd like to get a sample of your brain tissue.
Louis: Okay.
Parent
Re:I've always wondered (Score:5, Informative)
If it had been a loosely packed asteroid or a comet, it would have disintegrated into lots of small chunks and vaporised before reaching the ground.
The eyewitness reports are interesting:
"Kezhemskoe village. On the 17th an unusual atmospheric event was observed. At 7:43 the noise akin to a strong wind was heard. Immediately afterwards a horrific thump sounded, followed by an earthquake which literally shook the buildings, as if they were hit by a large log or a heavy rock. The first thump was followed by a second, and then a third.
We have friends who own a house next to quarry. Whenever there is a major explosion there always seems to two explosions heard; the first seems to be the shockwave travelling through the ground (a large dull sound thump) while the second is the shockwave through the air which sounds like a shotgun being fired. Then there is the all clear. So maybe the lake is the crater.
Parent
I vote for a comet (Score:3, Funny)
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"This water came from ice that sustained a comet 4.6 billion years. Don't you deserve the same? Buy Samethingastheothers Water. It's out of this world!"
I'm a bit worried (Score:2)
Re:I'm a bit worried (Score:5, Funny)
Considering YOU think that square miles are a measure of distance rather than area, and that kilometers are equivalent to miles, I'd say they have a better chance than you do.
Parent
more importantly (Score:5, Funny)
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he's trying to get us to retune our hats to let in the REAL frequency!
the speed of light / (3.26 kilometers) = 91.9608767 kilohertz
wait... (Score:2, Funny)
if you are, that's a fantastic bait hook right there, congratulations on crafting that lure
if you are not trolling us, and you are actually and earnestly interested in tesla causing tunguska, then congratulations to me
for reeling in with my conspiracy theorist joke a genuine paranoid schizophrenic
But don't worry about my incredulous attitude friend, I'M AN AGENT OF THE ILLUMINATI
i was sent here to distract you with silly jokes, to interfere with your concentration in the important search
Re: (Score:3, Funny)
The Tesla explanation is always quickly dismissed. My point is that quick dismissal never quashes underdog theories. What is needed is a thoroughly complete study of why it couldn't have been Tesla. I realize its sometimes impossible to disprove anything, but, afaik no one has even tried. "Its ridiculous, that's why," is not a scientific explaination. Many many many sane individuals, either for lack of specific scientific knowledge or real evidence to the contrary, think maybe its
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Phooey! (Score:2, Funny)
This is nothing but a bunch of bologna.
Dan East
Tesla connection? (Score:4, Interesting)
However, he did hear about the unexplainable event in Tunguska, and was thankful no one was killed, as it was clear to him that his death ray had overshot. He then dismantled his machine, as he felt it was too dangerous to keep it.
Re: Tesla connection? (Score:4, Informative)
Parent
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Googlink (Score:5, Informative)
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The lake already existed (Score:3, Interesting)
Re:The lake already existed (Score:4, Informative)
L. V. Dzhenkoul was born in 1904, so his personal memories of the 1908 Tunguska Event are minimal. Here he is recounting what he was told by his father V[asilii?] I[l'ich] Dzhenkoul and uncle I[van] I[l'ich] Dzhenkoul (both long dead by the time of Kolobkova's 1960 interview.
It seems highly likely to me that this individual is using "the mouth of the Cheko" as a landmark that is known to him, and is not necessarily indicating that this feature was present prior to the incident.
Parent
vurdalak.com article (Score:4, Funny)
2) how rich were they?
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Uni. Bologna homepage on Tunguska (Score:5, Informative)
In Soviet Russia ... (Score:3, Funny)
In Soviet Russia, asteroid finds you.
(Bracing for mod down ...)
Nothing new, exaggerated story by Nat. Geo. (Score:2)
Either that, or National Geographic is misrepresenting his Gasperini's quotes to make a story where there isn't one.
likely natural gas, not comet/asteroid/etc. (Score:4, Interesting)
Kundt W. (2001),
“The 1908 Tunguska catastrophe: An alternative explanation [ernet.in]”,
Current Science, 81: 399–407.
Kundt's paper explains the various problems with the comet/asteroid hypothesis. It also proposes an alternative hypothesis: that Tunguska was a natural gas leak (from the ground), that went on for days, building up, until ignited by a lightning strike.
This explanation seems to fit the observations well. Perhaps the main reason it has not gotten much attention is that it is not very exotic.
Re: (Score:3)
Area51 series by Robert Doherty, trite and overdone subject, yes. However, done extremely well. And you would get how this is (while bad humor, and possibly worth an 'overrated', not 'offtopic'.
Oh, and read the damn series. They are good books.
Re: (Score:2)
He probably got the offtopic mod because he said "I'll be hiding in my basement" instead of "I for one welcome our five limbed overlords" ;)
It is /. after all....
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I for one welcome our immortal, tall, sun-allergic overlords!
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Re: (Score:2, Funny)
Isn't this comment on slashdot a few times a month? I remember dupes being discussed before... ;)
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Re:X-files revisited (Score:4, Funny)
The Tunguska region is one of the largest uninhabited land areas on earth. One of the few places were an explosion could level 2000 square kilometres of forest while killing no people and very few advanced animals.
In other words the perfect place for a being with thought processes similar to ours to drop a dysfunctional engine core (or something similar) before it explodes.
Now what became of that pilot, his ship and possibly his crew? Chances are they made a safe landing in another remote area and were latter picked up by the alien equivalent of "American Automobile Association". The towing charge from within our atmosphere to the nearest repair shop might have ruined their whole day though
That scenario would explain the complete lack of debris. Depending on it's construction the jettisoned portion of the engine would all be vaporised in a massive "nuclear like" explosion.
Parent