The Tunguska Fireball, a Comet Chemical Bomb? Your thoughts

[xXTheOneRavenXx]

I read this article, and thought it would make a great topic of discussion:

Over a century ago, on June 30th, 1908 a huge explosion detonated over an unpopulated region of Russia called Tunguska. It is probably one of the most enduring mysteries of this planet. What could cause such a huge explosion in the atmosphere, with the energy of a thousand Hiroshima atomic bombs, flattening a forest the area of Luxembourg and yet leaving no crater? It is little wonder that the Tunguska event has become great material for science fiction writers; how could such a huge blast, that shook the Earth's magnetic field and lit up the Northern Hemisphere skies for three days leave no crater and just a bunch of flattened, scorched trees?

Although there are many theories as to how the Tunguska event may have unfolded, scientists are still divided over what kind of object could have hit the Earth from space. Now a Russian scientist believes he has uncovered the best answer yet. The Earth was glanced by a large comet, that skipped off the upper atmosphere, dropping a chunk of comet material as it did so. As the comet chunk heated up as it dropped through the atmosphere, the material, packed with volatile chemicals, exploded as the biggest chemical explosion mankind had ever seen…

12,000 years ago, a large object smashed into North America, causing global destruction. Dust and ash was released into the atmosphere, triggering global cooling and possibly causing the extinction of a number of large mammals around this time. The Tunguska event was of a similar energy to that catastrophic impact, but fortunately for us, Tunguska had a benign effect on the world. It simply exploded high in the atmosphere, flattened a region of Russia and vaporized.

"Significantly, the energy of the chemical explosion is substantially lower than the kinetic energy of the body," says Edward Drobyshevski of the Russian Academy of Sciences in St Petersburg, who has published his research into the Tunguska event. The fact that the Tunguska explosion energy is lower than what is expected of the kinetic energy of an object that hit the Earth from space is key to his work. Drobyshevski therefore concludes that the event must have been caused not by an asteroid or whole comet, it was actually caused by a fragment of comet material that fell off as the main cometary body skipped off the Earth's upper atmosphere. This means that the Earth was hit on a tangent and the fragment dropped comparatively slowly toward the surface.

Sounds reasonable so far, but how did the fragment explode? Using our new understanding as to what chemicals comets contain, Drobyshevski surmises the fragment was rich in hydrogen peroxide. This is where the magic happened. The explosion was not due to a rapid release of kinetic energy, it was in fact a hydrogen peroxide bomb. As the fragment descended, it heated up. As the reactive chemicals in the material got hot, they explosively disassociated to form oxygen and water, ripping the fragment apart. The Tunguska event was therefore a huge chemical bomb and not a "regular" comet-hits-Earth impact.

An interesting study. Not content with dropping asteroids on our planet, the Universe has started throwing hydrogen peroxide explosives at us too. Whatever next?

Source: http://www.technologyreview.com/blog/arxiv/23234/

What are your thoughts & insights?

 

[sacr3]

Naw, Aliens were testing very small Anti-matter bombs in our atmosphere to see the effects on the Human race.. Now 1/3rd of all humans get cancer, Good job Aliens.

Seriously though, I never really sat back and attempted to study this event.. though I've read little articles here and there, it does seem like an interesting event.

I'll just stick with massive exploding comet until we find a decent answer to it all, regardless, this was a good article.

thanks for the read and I must agree, that would be a decent explanation for it but it seems too complex and rare for it to happen.

 

[vogon13]

Seems like 'bouncing off the atmosphere' effect would be tightly constrained to objects of specific (low) mass and an extremely tight approach angle of only a few degrees.

I strongly suspect neither criteria were achieved by the hypothetical Tunguska 'parent' object.

Also, yield of explosion is related to speed and mass of incoming projectile. Do we know accurately to an order of magnitude the mass of the object ??


This idea is pretty close to specious IMO.

 

[MeteorWayne]

The latest peer reviewed research on the Tunguka event indicates it was a rocky asteroid that detonated about 5 km above the surface. That explanation describes the energy output quite well.

Also, there is NO data indicating any effect on the earth's magnetic field.

This author is a woo-woo. In examining his work, he regularly submits articles to peer reviewed journals, but it seems they are never accepted. :roll:

 

[xXTheOneRavenXx]

Your welcome fellas Just trying to do my part and post topics that might interest you.
I read the original articles as well and thought a rocky asteroid exploding 5km above the surface (as MeteorWayne pointed out) was the cause. However after reading this article I was curious about the possibility of such an event being the cause. I'm sure a very porous asteroid heating up as it passed through the atmosphere would explode regardless of it's size. If this object exploded, how come no one has found any fragments?

 

[MeteorWayne]

Being a rocky asteroid, it pretty much vaporized in the explosition Tektites have been found, which are tiny bits of melted debris that solidified. Note the asteroid that created Meteor Crater in Arizona was almost pure Iron-Nickel (he said as he fondled his piece of the Canyon Diabo meteorite)

If you want to learn some more about the subject, I highly recommend Norton's "Rocks From Space". Might be in your local library.

 

[xXTheOneRavenXx]

If I get some time I will read more up on it. I was just intrigued by this man's story. I think the article I read was quite old because it didn't mentions fragments being found, but thank you for that knowledge. (Brain is about to explode from visiting Space.com, lol)

 

[MeteorWayne]

Well, just to be clear, tektites are not really fragments. It is vaporized material that was injected into the upper atmosphere, then cools and hardens, and spreads almost worldwide.

 

[DrRocket]

"Significantly, the energy of the chemical explosion is substantially lower than the kinetic energy of the body," says Edward Drobyshevski of the Russian Academy of Sciences in St Petersburg, who has published his research into the Tunguska event. The fact that the Tunguska explosion energy is lower than what is expected of the kinetic energy of an object that hit the Earth from space is key to his work. Drobyshevski therefore concludes that the event must have been caused not by an asteroid or whole comet, it was actually caused by a fragment of comet material that fell off as the main cometary body skipped off the Earth's upper atmosphere. This means that the Earth was hit on a tangent and the fragment dropped comparatively slowly toward the surface.

Sounds reasonable so far, but how did the fragment explode? Using our new understanding as to what chemicals comets contain, Drobyshevski surmises the fragment was rich in hydrogen peroxide. This is where the magic happened. The explosion was not due to a rapid release of kinetic energy, it was in fact a hydrogen peroxide bomb. As the fragment descended, it heated up. As the reactive chemicals in the material got hot, they explosively disassociated to form oxygen and water, ripping the fragment apart. The Tunguska event was therefore a huge chemical bomb and not a "regular" comet-hits-Earth impact.

An interesting study. Not content with dropping asteroids on our planet, the Universe has started throwing hydrogen peroxide explosives at us too. Whatever next?

Source: http://www.technologyreview.com/blog/arxiv/23234/

What are your thoughts & insights?[/quote]

Not only is MeteorWayne's explanation more satisfying and rational, it does not violate simple physics.

Whether or not a body of the type described might provide the fuel for a chemical explosion, one cannot ignore the kinetic energy, which is clearly stated to be greater than the chemical energy available. A piece of an incoming body will have the speed of that body, and if it breaks off will carry the associated kinetic energy (1/2 mv^2). That energy does not just go away, but must be converted to heat if the speed of the constituents of the body are subsequently reduced to zero relative to the earth.

To pretend otherwise is to abrogate conservation of energy, and that would be a bigger mystery than the Tugunska event itself.

 

[xXTheOneRavenXx]

So in other words (if I'm getting this correct), if it were as he said in the article then we would have had a crater anyhow because the fragment would have had the same kinetic energy as the body itself?

 

[silylene]

If I get some time I will read more up on it. I was just intrigued by this man's story. I think the article I read was quite old because it didn't mentions fragments being found, but thank you for that knowledge. (Brain is about to explode from visiting Space.com, lol)

I am glad you are asking.

The kinetic energy far exceeds the chemical energy by orders of magnitude, even if you assume the meteor was composed of a high explosive, such as RDX.

 

[MeteorWayne]

In addition, there is no confirmed crater from Tunguska, since it exploded (vaporized) 5-10 km above the surface. There was a suggestion in a paper last year that a small crater has been discovered, but that has yet to be confimed.

 

[Smersh]

The latest peer reviewed research on the Tunguka event indicates it was a rocky asteroid that detonated about 5 km above the surface. That explanation describes the energy output quite well.

Also, there is NO data indicating any effect on the earth's magnetic field.

This author is a woo-woo. In examining his work, he regularly submits articles to peer reviewed journals, but it seems they are never accepted. :roll:

I have read reports that the Tunguska object detonated several km above the surface as well in the past, but it has always puzzled me. How could a rocky asteroid explode before it strikes the ground?

In addition, there is no confirmed crater from Tunguska, since it exploded (vaporized) 5-10 km above the surface. There was a suggestion in a paper last year that a small crater has been discovered, but that has yet to be confimed.

In fact, here's an article from Space.com from a while back that I posted on another board a few months ago, with a picture of Lake Cheko (suspected of being the crater) :

Posted: 26 June 2007
06:27 am ET

Story from Space.com

Crater Could Solve 1908 Tunguska Meteor Mystery

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."

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

Full story: http://www.space.com/scienceastronomy/0 ... rater.html

 

[MeteorWayne]

Smersh enquired: "I have read reports that the Tunguska object detonated several km above the surface as well in the past, but it has always puzzled me. How could a rocky asteroid explode before it strikes the ground?"



Physics, my friend The front edge is slamming into the atmosphere at at least 11.2 km/sec, and more commonly for asteroids more than 20 km/sec. To such an object, it's like hitting a brick wall. The back edge (behind it) is much less than atmospheric pressure (due to the wake, i.e. the air being pushed out of the way by the front edge, and not having enough time to fill in the space behind). When the difference in pressure between the front and the back exceeds the strength of the rock, it shatters. Rock is relatively weak when subjected to these extreme pressures.

 

[Smersh]

Thanks Wayne - that explanation makes sense. I guess a rocky asteroid then (rather than the "comet chemical bomb" theory in the op) is much more likely then, do you think? (Especially as the article in the op seems to be verging on"pseudo-science," judging by some other comments here.)

 

[MeteorWayne]

In my judgement, a rocky asteroid seems the most likely. Certainly a comet cannot be discounted as a possibility, but not as a "chemical explosion". Because comets can hit at speeds up to 72 km/sec, they have far more kinetic energy (E= 1/2mass x velocity squared), so a much smaller object can cause the same effects. However, that does not fit with the eyewitness accounts, which fit an asteroid traveling around the sun the same direction as earth much better.

Also the idea of a comet "dropping off a piece" to explode just doesn't work. How would it slow down and drop? Physics says it can't work.

And yes, this guy is a woo woo of the highest order

 

[DrRocket]

So in other words (if I'm getting this correct), if it were as he said in the article then we would have had a crater anyhow because the fragment would have had the same kinetic energy as the body itself?

No.

A fragment would not have the same kinetic energy as the body itself. It would have a fraction of the kinetic energy proportinal to the fraction of the total mass in the fragment -- but it was stated that the kinetic energy of the fragment was much greater than the chemical energy. You cannot ignore the kinetic energy in that sitiuation -- it is the largest portion of the available energy and it will be converted to heat at some point.

Whethere or not there is a crater depends on how the energy is released, and eventuall turns into heat. If it is released by a direct impact then you get a big crater. If is released high in the atmosphere then you don't.

Look, eventually almost all energy is kinetic energy. Chemical energy turns into heat, which is just kinetic energy at a molecular level. Temperature is the kinetic energy of translation of molecules and heat energy is the kinetic energy of not only translation but also other modes of motion at the molecular level. What we call kinetic energy of a body is simply the energy of translation of the molecules in the mean direction of motion, taking out the random motion that we call temperature. You can't ignore any large quantity of energy when evaluating the physics of an event like the Tunguska fireball.

 

[kg]

I don't even see hydrogen peroxide listed as an ingredient of a comet.
http://en.wikipedia.org/wiki/Comet

 

[xXTheOneRavenXx]

A fragment would not have the same kinetic energy as the body itself. It would have a fraction of the kinetic energy proportinal to the fraction of the total mass in the fragment -- but it was stated that the kinetic energy of the fragment was much greater than the chemical energy. You cannot ignore the kinetic energy in that sitiuation -- it is the largest portion of the available energy and it will be converted to heat at some point.

Whethere or not there is a crater depends on how the energy is released, and eventuall turns into heat. If it is released by a direct impact then you get a big crater. If is released high in the atmosphere then you don't.

Look, eventually almost all energy is kinetic energy. Chemical energy turns into heat, which is just kinetic energy at a molecular level. Temperature is the kinetic energy of translation of molecules and heat energy is the kinetic energy of not only translation but also other modes of motion at the molecular level. What we call kinetic energy of a body is simply the energy of translation of the molecules in the mean direction of motion, taking out the random motion that we call temperature. You can't ignore any large quantity of energy when evaluating the physics of an event like the Tunguska fireball.

So in other words, my translation reads: Buddy has no idea what he's talking about then, and only fantasizing a solution?

 

[DrRocket]

So in other words, my translation reads: Buddy has no idea what he's talking about then, and only fantasizing a solution?

Who is Buddy ?

I suspect that the reporter is the one who has things wrong. Any reasonable scientist will be well-acquainted with conservation of energy.

Whether or not you get a crater is a question involving quite a bit more than just how much energy is released. Penetration mechanics is complex subject, and energy is only one of the important factors. You can get a crater from the impact of an object with a lot of kenetic energy. You can get a crater from a large chemical explosion. you can also get a big hole from a diesel-powered shovel. Similarly you can get widespread destructin from a chemical explosion higher in the atmosphere, from the conversion of kinetic enrgy to heat higher in the atmosphere, or from a strong wind.

The article simply did not address all the necessary and relevant physics. In my experience that means that the reporter did not understand the story that was writing about, although the scientist probably did. You need to be very careful in reading articles written by non-specialists for consumption by the general public. There is quite often a large distortion factor. I personally have found that when an article with which I have some direct involvement appears in the popular press, that the story is totally unrecognizable to me. It is particularly bad with respect to scientific and technical subjects, but I have seen rathre bad distortions in other articles as well (even after being assured beforehand by the writer that the story would be accurate and that the reporter was familiar with the subject matter).

 

[MeteorWayne]

Dr Rocket, I think you far overestimate the competence of the scientist who wrote the (not accepted) paper. The guy is a woo-woo, part of the russian wacko science crowd. In fact if you look at his cv of papers, you will find that none of them have ever been accepted, only submitted and revised, sometimes for many years.

 

[DrRocket]

Dr Rocket, I think you far overestimate the competence of the scientist who wrote the (not accepted) paper. The guy is a woo-woo, part of the russian wacko science crowd. In fact if you look at his cv of papers, you will find that none of them have ever been accepted, only submitted and revised, sometimes for many years.

You are undoubtedly correct, and the remarks on the blog do indicate that he has the reputation of being a nut.

Where did you find his cv? The links that I say only go to a blog. I have not seen an original draft of the article, published or submitted for review, only the article quoted. I'll see if I can find the cv or draft of the paper somewhere.

However, my observations and opinions regarding the accuracy of reporting remain unchanged. In fact this topic serves to reinforce them. Why would a reputable reporter bother to publish an article based on an unpublished snd probably unpublishable article.

 

[MeteorWayne]

Sorry, Dr Rocket, it's buried in the blog:

http://arxiv.org/find/all/1/all:+Drobys ... /0/all/0/1

PLEASE put on your tinfoil hat first

 

[DrRocket]

Sorry, Dr Rocket, apparently someone edited out the link:

http://arxiv.org/find/all/1/all:+Drobys ... /0/all/0/1

PLEASE put on your tinfoil hat first

I found the original article http://arxiv.org/ftp/arxiv/papers/0903/0903.3309.pdf and I looked through the articles listed at the site that you kindly provided.

The original article makes it clear that Drobyschevski is quite aware of the high kinetic energy of the hypothesized body, and did not simply ignore it. That does not mean that his proposed mechanism is correct, or even plausible. It does indicate to me that the reporter got things a bit scrambled.

In looking through the list of Arxiv articles from this guy, it appears that some of them have been published. That in itself doesn't mean anything much either. There are lots of junk journal articles these days. Even articles appearing in some "peer reviewed" journals ought to be viewed with a great deal of suspicion -- recall the articles by Oscar Manuel et al.

It tend to think that this guy is all wet. I have no faith or interest whatever in his "new explosive cosmogony". That is very likely some of the junkiest of junk science. But he is being aided and abetted in publicizing junk by what seems to be a reporter looking for a sensational story. To compound the problem the reporter doesn't seem to understand the physics either. So, it looks to me like incompetent reporting of junk science -- a poor combination.

Does a tinfoil hat offer protection when it is raining horse manure ?

 

[MeteorWayne]

From what I've heard, you need at least a triple layer...