Tunguska Blast Was a Small Asteroid 277
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."
I've often wondered (Score:5, Interesting)
Re:The Gist (Score:5, Interesting)
Perhaps these dramatic presentations aren't really that helpful. It could be that volcanoes won't erupt under Los Angeles, ice hurricanes won't hit New York, and 10.0 earthquakes won't toss Los Angeles into the Pacific Ocean (and why isn't Chicago or London ever destroyed?). It might be helpful for you to calculate the area that the Tunguska Blast caused devastation, divide by the surface area of the earth, multiply it by the surface area of our major population centers, and then multiply it by the probability of this type of event occurring in the next 50 years. But this is boring and lacks the 'scary thinking' and drama, right?
The Earth's surface is mostly H2O (Score:2, Interesting)
Re:Doh! (Score:3, Interesting)
2) A tiny bit of antimatter
Nah, would be no biggie. (Score:5, Interesting)
As for the possibility of similar-sized asteroid impacting the ocean instead of exploding above it--well, the article only says that the asteroid is now thought to be "only a fraction as large as previously published estimates". That doesn't tell us anything. The Tunguska asteroid may or may not have been large enough to trigger a tsunami had it impacted an ocean instead of exploding over land. I'm going to assume that an impact will usually be less energetic (though perhaps more concentrated) than a heat-induced explosion, in which case no, the Tunguska asteroid never posed a significant threat to the world as a whole.
That said, the Tunguska explosion is still fascinating as hell. I know that there's a lot of very strong evidence pointing to the asteroid theory, but it's still fun to toy with conspiracy theories. The atomic bomb was first being conceived of, Tesla's Wardenclyffe Tower was being tested (by some accounts, it was brought online the day before the explosion)... it's all absolute rubbish, to be frank, but it's very entertaining rubbish.
Unlikely to be an asteroid (Score:4, Interesting)
An alternative explanation was proposed by Wolfgang Kundt, a researcher at the Institut für Astrophysik, University of Bonn:
Kundt W. (2001),
“The 1908 Tunguska catastrophe: An alternative explanation [ias.ac.in]”,
Current Science, 81: 399–407.
The basic proposal is that there was a natural gas leak, from the Earth. The gas rose to a certain height, then drifted downwind. After several days, a lightning strike ignited the airborne gas, and the flame then traveled along line (of drifted gas), to the ground source.
It is worth reading the article. An asteroid impact is sexy, but the alternative explanation fits with the data much better.
Horizon (Score:4, Interesting)
Re:Unlikely to be an asteroid (Score:5, Interesting)
A Comet (Score:3, Interesting)
Evidence is compelling. . . (Score:3, Interesting)
1. That there have been far more events in recorded history similar to Tunguska which have been volcanic or geologic in nature than have been due to cometary impact, raising the question of probabilities. --Mt. Saint Helens blowing its top in 1980 is an example, as was Krakatoa in 1983. There was also the 1986 limnic eruption of 1.6 million tonnes of CO2 from Lake Nyos which suffocated 1,800 people in a 20 mile radius. Sometimes it's a methane outgassing which can blow up, (one event was described in the linked paper which damaged a commuter jet plane). The Earth 'burps' on a regular basis. Rocks causing similarly huge events are far less frequent, (as in, there haven't been any at all in the last century).
2. That there was swamp land in the center of the Tunguska caldera. This is a typical place for methane to build up.
3. The directions in which the trees had been knocked down indicated two discrete blast points some distance from one another.
4. There were odd glowing clouds seen over the area in the nights leading up to the explosion which could be explained by methane collecting in the sky.
5. No impact crater was found.
6. No meteorite was found. (--Though there was a concentration of microscopic glass spheres in siftings of the soil and chemical analysis showed that the spheres contained high proportions of nickel and iridium which are often found in meteorites, hinting that they might have been of extraterrestrial origin. But still. . . No rock.)
Every year there are geologic events which result in ash plumes and outgassings all over the world. While there is plenty of evidence of past cometary impacts which had a significant effect upon the Earth, they are all very old; the number of catastrophic events due to impact events over the last century has been pretty much zilch. If we're going to throw Occam at this, (and I am very hesitant in invoking that old and oft-misused saw), then it seems much more probable that Tunguska was the result of a methane outgassing and subsequent explosion. Anyway, the paper is an interesting analysis and it leaves me uncertain as to what to think, as there is still some good arguments for the event having been an impact. I'd be curious if anybody out there has any other info to contribute which might make the picture more clear.
-FL
Re:The Gist (Score:4, Interesting)
By reform I'm guessing that you mean reform via gravity? And since we are dealing with asteroids would it be safe to say that 'later' is later on an astrological time scale?
On that scale, I can live with a 'temporary' fix. (Live, have children, grow old, die, kids grow old...)
Re:The Gist (Score:1, Interesting)
Re:The Gist (Score:4, Interesting)
Let's pick the middle ground and say four megatons, that's 1.67E16 joules. From what I can see, non-metallic asteroids really aren't all that dense because they tend to be very porous, and it seems likely that a metal asteroid wouldn't explode in this manner but would instead impact and bury itself. So call it 2600 kg/m^3. Assuming Earth escape velocity is probably a safe bet as well; it's possible the thing was an extra-solar object but not likely. So that's 11km/sec. Unless I'm screwing something up, I get a mass of 276,000,000 kg, and a spherical asteroid 30 meters in diameter.
I am on firm ground there? I mean, the only source of energy driving the explosion is the kinetic energy of the asteroid, it's just heating the thing up and making it go boom.
Re:Diameter ~ 50 meters (Score:1, Interesting)
The only way for ALL this energy to be released is for the kilogram of water to be totally annhilated. This process involves the complete destruction of matter, and occurs only when that matter meets an equal amount of antimatter
The asteroid would have exploded due to the heat of atmospheric entry, converting kinetic energy to explosive force, not a nuclear blast, though the magnitudes rival nuclear blasts.
Perhaps someone else can do the math for a kinetic conversion.
Re:Evidence is compelling. . . (Score:3, Interesting)
Compelling evidence? Lets see...
1. That there have been far more events in recorded history similar to Tunguska which have been volcanic or geologic in nature... Mt. Saint Helens ... Krakatoa ... Lake Nyos... And which of these are examples of the supposed megaton range methane gas explosions? Why... none of them. Sorry, unrelated geophysical events don't provide any precedent for the proposed mechanism. The notion seems a bit difficult to buy into - the explosive limits for methane in air is usually quoted at 5-15% by volume, to make a mammoth blast you would need to establish this specific concentration range with millions of tons of methane, and have it ignited at the proper time. How does this happen geophysically? Any actual examples?
2. That there was swamp land in the center of the Tunguska caldera. This is a typical place for methane to build up. But... millions of tons? Capable of sudden release? People should be finding commercial exploitable methane gas deposits in the surface strata of swamps I should think.
3. The directions in which the trees had been knocked down indicated two discrete blast points some distance from one another. If this was observed, a twin asteroid would be a reasonable explanation (recent probe and radar evidence shows asteroids to frequently consist of loosely bound multiple bodies).
4. There were odd glowing clouds seen over the area in the nights leading up to the explosion which could be explained by methane collecting in the sky. Reports on the Tunguska event I have seen report glowing clouds in the sky afterward, not before.
5. No impact crater was found. Only the very rare iron asteroids are strong enough to make ground impact in this size range. The far more common stony bodies will fragment and explode in the air. This is a complete red herring.
6. No meteorite was found. This is a red herring like 5. It exploded high in the air. The extraterrestrial particles found are the meteorite.
The whole notion that this is an unprecedented event that requires alternate explanation is utterly wrong. Atmospheric explosions of extraterrestial bodies are regularly documented events. The Defense Support Program (DSP) has monitored atmospheric explosions since the 1960s and has found Hiroshima-sized (16 kt) events occurring about once a year. A simple statistical distribution permits calculating the frequency of larger events, a 10 Mt event is expected once very 120 years. See: an item about this in the Acoustical Society of America's newsletter [aip.org]. This being the case, there is really no anomaly here to be "explained away". Bolide explosions are a regular occurrence and we should see some in the megaton range in the historical record - most of course occur over open oceans and have had few witnesses and left no evidence.
Re:The Gist (Score:1, Interesting)
The majority of the U.S. lies in the interior, specifically the Midwest and the deep South. Most of the people living there are religious, dogmatic, and deeply mistrustful of the coasts (primarily New York and California, aka "Damn Yankees"). These people don't like science, have major problems with their educational infrastructure ("Intelligent design", anyone?) and spend much of their time watching television produced by the coasts, which tends to exacerbate their built-in inferiority complexes.
As long as New York, Massachusetts, and California exist, the interior will never be anything more than a grade-B player. Almost all of the wealth (both monetary and intellectual) of this country is in these three states.
Thus, films displaying the utter destruction of these locations are very popular in most of the country, giving the uneducated rednecks out there a huge burst of self-righteous Schadenfreude [wikipedia.org]. These films also tend to allow these people to fantasize about their mythical God taking vengeance against "them faggy New York intellectuals".
Support for this theory can be found in the fact that these movies:
1) Depict scientists as being powerless against whatever onslaught is approaching (asteroid, ice age, etc).
2) Mention God and faith a LOT ("All we can do now is pray").
3) Depict the more scientific minded people dying in one fashion or another while stupider religious people survive with "faith".
4) Always depict someone (usually a pair of well-educated intellectuals) fornicating, then dying, with the definite assumption that it was divine retribution.
5) Isn't it interesting that in the recent ice age movie, they fled to Mexico, a predominantly CATHOLIC COUNTRY???
Look. It's basically "apocalypse porn" for religious rednecks, ok? OF COURSE New York and L.A. are always destroyed. OF COURSE the Midwest and South are spared.
They leave London alone because most rednecks can't find it on a map.