Tunguska Event, 100th anniversary

[Northern Neil]

100 years ago yesterday 2000 square miles of Siberian forest was flattened by a mid - air explosion which was thought to have been caused by a cometary fragment entering the Earth's atmosphere. Tungus tribesmen still do not approach the area, and fallen trees are still to be seen.

 

http://russiatoday.com/features/news/26793...CFQ8WQgodg3xitw

 

http://news.bbc.co.uk/1/hi/sci/tech/7470283.stm

Edited July 1, 2008 by Northern Neil

[Faustus]

[caldrail]

Impacts are nothing unusual in earths history. Earth was formed by them, as large asteroidal bodies collided after gravity set them on a collision course. The original earth was a non-hospitable world, smaller than the earth of today. Its theorised that another planet - Thea - collided and this formed the modern earth and moon. That must have been quite a bang! The remains of craters are evident all over the surface of the world and in fact the frequency of such events is nothing like it once was.

 

Tunguska is unusual because its the only example of an airblast recorded. I'm going to discount tales of alien spacecraft - there's absolutely no evidence for that at all - but it does beg the question what the object was and why did it explode above the earths surface? very strange.

[Faustus]

Tunguska is unusual because its the only example of an airblast recorded. I'm going to discount tales of alien spacecraft - there's absolutely no evidence for that at all - but it does beg the question what the object was and why did it explode above the earths surface? very strange.

Consider the calculation methods for the size of the body that made the Chicxulub Crater for some perspective: "Using estimates of the total amount of iridium in the K

Edited July 3, 2008 by Faustus

[Northern Neil]

The BBC article estimates the blast at 1'000 times that of the Hiroshima bomb. I find a yield of 14 megatons a bit difficult to believe, and there doesnt appear to have been a fireball. 1 megaton I can accept.

Edited July 3, 2008 by Northern Neil

[Faustus]

The BBC article estimates the blast at 1'000 times that of the Hiroshima bomb. I find a yield of 14 megatons a bit difficult to believe, and there doesnt appear to have been a fireball. 1 megaton I can accept.

 

The land area laid waste and immediately leveled (wooden structures) by Hiroshima

Edited July 3, 2008 by Faustus

[ASCLEPIADES]

100 years ago yesterday 2000 square miles of Siberian forest was flattened by a mid - air explosion which was thought to have been caused by a cometary fragment entering the Earth's atmosphere. Tungus tribesmen still do not approach the area, and fallen trees are still to be seen.

 

http://russiatoday.com/features/news/26793...CFQ8WQgodg3xitw

 

http://news.bbc.co.uk/1/hi/sci/tech/7470283.stm

Salve, Amici.

Wow; after a couple of never-ending historical arguments over Latin gossip, nothing like a cosmic ephemeron to remind us our true place within the universal scheme.

 

The most unusual fact of the Tunguska event was the obvious discrepancy between its known physical effects and the absence of any impact crater. I think Collins and Bland are right in dismissing Longo's Lake Cheko as the crater; after so many years, it seems old Carl Sagan's explanation (a "dirty ice" object, ie a comet's head) is still the best one.

 

One cannot help but wonder how many historical facts would we be able to explain with such a destructive event leaving so little physical evidence at any other place and time.

 

All that said, I find irresponsible (to say the least) Dr Richard Crowther's quoted assertions (sic: "The surveys suggest that objects of this size are numerous enough to anticipate similar events in the relatively near future").

 

I must assume Dr. Crowther would like more money for his NEO (United Nations Near Earth Object) programme, and/or that he enjoys to see his face and name on the news.

 

Dr. Crowther can't ignore that Humankind has nicely survived so far without any additional protection than that given by simple probability, and that current research (including his own team) has not found anything that can even remotely suggest that will change in the foreseeable future (For example, check out the Earth Impact Database).

Edited July 4, 2008 by ASCLEPIADES

[Faustus]

Wow; after a couple of never-ending historical arguments over Latin gossip, nothing like a cosmic ephemeron to remind us our true place within the universal scheme.

 

The most unusual fact of the Tunguska event was the obvious discrepancy between its known physical effects and the absence of any impact crater.....

The Tektite Mystery

 

There are across America, and other parts of the world as well, large oval elliptical areas where green glassy tektites may be found. The shape and sizes of these areas are now called

Edited July 4, 2008 by Faustus

[caldrail]

A little tip ladies and gentlemen - always check Wikipedia before engaging brain....

 

It turns out that unbeknown to me the tunguska event is not unusual. Such an event is believed to occur once every three hundred years on average somewhere around the world, and US defence analysis suggests that airburts in the upper atmosphere from small objects are regular occurences.

 

As for distibution of the craters of more physical impacts, remember that the continents have moved around a lot over the ages. The earths landmass has migrated northwards since the oceans formed.

 

I'm reminded of a meteorite impact in the arabian desert witnessed by explorers there searching for lost ruins. A hundred years later, the crater had almost vanished beneath the sand. Exposed craters will weather away.

[Faustus]

It turns out that unbeknown to me the tunguska event is not unusual. Such an event is believed to occur once every three hundred years on average somewhere around the world, and US defence analysis suggests that airburts in the upper atmosphere from small objects are regular occurences.

 

As for distibution of the craters of more physical impacts, remember that the continents have moved around a lot over the ages. The earths landmass has migrated northwards since the oceans formed.

 

Heck C.

 

That's the whole idea. And the larger, the less frequent

Edited July 4, 2008 by Faustus

[ASCLEPIADES]

A little tip ladies and gentlemen - always check Wikipedia before engaging brain....

 

It turns out that unbeknown to me the tunguska event is not unusual. Such an event is believed to occur once every three hundred years on average somewhere around the world, and US defence analysis suggests that airburts in the upper atmosphere from small objects are regular occurences.

 

As for distibution of the craters of more physical impacts, remember that the continents have moved around a lot over the ages. The earths landmass has migrated northwards since the oceans formed.

 

I'm reminded of a meteorite impact in the arabian desert witnessed by explorers there searching for lost ruins. A hundred years later, the crater had almost vanished beneath the sand. Exposed craters will weather away.

Salve C. Good tip. If you check Wikipedia carefully, you will see why the Tunguska event was highly, (HIGHLY) unusual and why it has engaged the brain of so many people.

 

A regular airburst from the upper atmosphere wouldn't explain:

- The destruction of such big area of Siberian forest.

- An earthquake equivalent to (estimated) Richter 5.0

- Fluctuations in atmospheric pressure strong enough to be detected in Great Britain.

- An observed decrease in atmospheric transparency in the United States from the suspended dust that lasted for several months.

 

At the risk of overstating the obvious, any regular meteorite of enough volume to explain such massive release of energy MUST have left a huge crater.

 

Continents haven't moved beyond centimetres for the last century and the famous Kulik's expedition was there at 1927.

 

It seems quite unlikely Lake Cheko can be such crater (as Longo proposed) among other reasons because there are trees on its shore actually older than the impact itself (as Collins and Bland rightly stated).

[Faustus]

A regular airburst from the upper atmosphere wouldn't explain:

- The destruction of such big area of Siberian forest.

- An earthquake equivalent to (estimated) Richter 5.0

- Fluctuations in atmospheric pressure strong enough to be detected in Great Britain.

- An observed decrease in atmospheric transparency in the United States from the suspended dust that lasted for several months.

 

At the risk of overstating the obvious, any regular meteorite of enough volume to explain such massive release of energy MUST have left a huge crater.

 

Salve A.

 

 

All for the sake of argument (from a non-scientist)

Except for the R-5 quake, which is only conjecture, (as are all my remarks) all of the conditions can be met by a tenuously agglomerated snowball interlaced with space dust serving to weld ancient collision aggregates into one large cometary object.

 

If the height of the

Edited July 4, 2008 by Faustus

[ASCLEPIADES]

A regular airburst from the upper atmosphere wouldn't explain:

- The destruction of such big area of Siberian forest.

- An earthquake equivalent to (estimated) Richter 5.0

- Fluctuations in atmospheric pressure strong enough to be detected in Great Britain.

- An observed decrease in atmospheric transparency in the United States from the suspended dust that lasted for several months.

 

At the risk of overstating the obvious, any regular meteorite of enough volume to explain such massive release of energy MUST have left a huge crater.

 

Salve A.

 

 

All for the sake of argument (from a non-scientist)

Except for the R-5 quake, which is only conjecture, (as are all my remarks) all of the conditions can be met by a tenuously agglomerated snowball interlaced with space dust serving to weld ancient collision aggregates into one large cometary object.

 

Faustus

Salve, F. We agree. You miss my point.

As I stated previously, I also still find the old Carl Sagan's theory of the "comet's core" impact as the most likely explanation (I'm not sure he was the author, but he surely promoted it).

 

The findings of the Tunguska's Event can't be explained by the impact of any "regular" meteorite (ie, rocky and/or metallic last time I checked).

 

I think even the earthquake can be explained by the "comet's core" impact theory.

BTW, that earthquake was no conjecture, as it was detected by multiple seismic stations across Eurasia at the time.

As the Richter Scale wasn't used at 1908, the retrospective attrribution of a "5.0" value is an indirect estimation, not a "conjecture".

 

From where I am, the main problem for the "comet's core" explanation is that such phenomena hasn't been observed twice, as far as I'm aware.

Edited July 4, 2008 by ASCLEPIADES

[Faustus]

From where I am, the main problem for the "comet's core" explanation is that such phenomena hasn't been observed twice, as far as I'm aware.

A., please help me with that.

Not being a scientist I

Edited July 4, 2008 by Faustus

[ASCLEPIADES]

From where I am, the main problem for the "comet's core" explanation is that such phenomena hasn't been observed twice, as far as I'm aware.

Three links on the subject of Icy Meteors or Small Comets

Small Comets ~ http://smallcomets.physics.uiowa.edu/

The Original Discovery ~ http://smallcomets.physics.uiowa.edu/blackspot.html

New Optical Search; Different Telescope, Same Small Comets ~ http://smallcomets.physics.uiowa.edu/iro/iro2.html

Gratiam habeo for those links, F. You have done a great research.

 

I agree dirt ice objects do impact the Earth and other celestial bodies, even if I don't know how often they do.

 

What I think has been reported only once is, again, the Tunguskan Event discrepancy; any impact with so much evidence of so big collateral energy release without actually leaving any crater or equivalent finding.

 

As I'm no expert, I can't be totally sure that the momentum of a dirt ice object of the proper size to be vaporized just some hundreds of metres away from hitting the Siberian surface would be enough to replicate all the described findings (and non-findings too).

 

Replicability is one of the main bases for scientific knowledge (ie, if we replicate the critical conditions, the resultant phenomenon predictably happens). Conversely, its absence must be considered a caveat for any scientific hypothesis.