It was an energetic event that occurred over Tunguska, but what caused it? (Don Davis)
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: The Physics arXiv Blog
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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!
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@Jon Hanford
That wasn’t my claim though was it?
AT NO POINT did I say that Comet Hyakutake or Comet West had snuck into the inner solar system.
What I did say, however, was that the Great Eclipse Comet of 1828 snuck into the inner solar system without being observed, and that the great eclipse comet was a spectacular comet (because of it’s designation as a great comet) LIKE comets Hyakutake and West.
Get it?
I was comparing the three comets in terms of visual apperance and how spectacular they were, NOT suggesting that all three snuck into the inner solar system, so that assertion is quite simply false.
Dear Trippy, my apologies for the misunderstanding.
Jon.
Accepted
Revisiting Tunguska after 100 years is all fine and interesting, but Drobyshevski seems to be making news out of old news… I mean, it’s pretty clear that Tunguska’s culprit was either a comet or an asteroid, which exploded while still in the atmosphere, like many objects do explode on their path to earth. The witness accounts support the theory, as well as findings at the location. What there’re no accounts for is a comet visible with naked eye during that time, so Drobyshevski’s idea that Tunguska’s impactor was, in fact, a part of a comet doesn’t really hold the water, imho.
@aqua – invoking mirror matter to explain this is even stranger than what Drobyshevski has written.
@4gea – Tunguska was either a meteor or small rocky fragment of a comet. Actually it has to be fairly rocky based on mineral evidence. If it were an asteroid or a full sized coment the bang would have be far worse (please see previous comments). Also please see the many comments from others that indicate we have missed comets and major ones at that. A small piece could easily be missed even today.
Aside from Drobyshevski’s strange claims at the end, what he’s proposed isn’t as far off the deep end as what we might think. When I went through the paper I found the “why” that he used to invoke all of this. He suggests that the explosion was too small for any of the predicted impactors. That’s something that could be checked based on the numbers he and others have. I suspect the range of error in the data outweighs the thing he’s trying to explain. But I haven’t tried the math. That’s why a peer review would be helpful.
To fix the perceived problem he suggests that the impactor came in slower than thought. To do that he proposes a fragment coming off a larger piece. The larger piece keepin most of the kinetic energy.
He also brings up discrepancies in the trajectory and suggests a turn (or rather a deflection) caused by a partial explosion. I’d never seen that before and have no idea if its necesary to explain anything.
I’m guessing he turns to the chemical part of his theory because the speed of the impactor he’s suggesting may be too slow to cause the blast at all. Or maybe he’s got an agenda. I’m not even going to try and figure it out.
He only jumps the couch in the very last paragraph with the whole bit about Callisto exploding.
Drobyshevsky is a typical crackpot believing Tunguska was seeded by exploding ices of Ganimede or Callisto and stuff like this. He has also previously `solved’ the problem of dark matter:-)
Just thought I didn’t want this guy to be associated with the Russian Academy of Science – despite he’s working within the structure thereof.
Every possibility has been thrown out but this one, as far as I know, but what about a small gamma ray burst??
No evidence of anything hitting the ground, though a small comet, asteroid or meteorite would vaporize. I’m just saying though…super bright light coming in, no crater or impact site left behind. The atmosphere was left glowing for days after the event. Wouldn’t a gamma ray burst super charge any atoms and matter in the atmosphere to the point of luminescence?
@ Eric Near Buffalo : A GRB related event occuring in 1908, while not positvely ruled out, would leave several unanswered questions. First question that comes to me, why no observations of a visible object in the night sky either prior to, or immediately after the event. Surely this would be a bright nighttime occurance if the GRB is within the critical 1000 l.y. distance for any Earthly damage to occur. Lighting of the nighttime( and daytime) sky would also need to be observed to fit with a GRB origin. Strong gamma radiation impinging on the Earth would not be so small and would not knock down trees for thousands of miles. A good primer on the short and long term effect of a nearby GRB & life on Earth was published today on the arXiv site & can be found here: http://arxiv.org/ftp/arxiv/papers/0903/0903.4710.pdf .This paper “Gamma Ray Bursts as a threat to Life on Earth” by BC Thomas goes into great detail on the effect of a nearby (1000 l.y.) GRB aimed at Earth covering Earth’s entire lifetime, is a great read and has extensive links to relevant published papers on the matter. You might want to check it out.
@ Jon Hanford
Thank you for your reply. I appreciate the fact that you didn’t just laugh it off. I will check out that article. I did see a show a while back about Gamma Ray Bursts on the History Channel sometime at the end of last year…I believe it was a part of the channel’s “Mega Disasters” series. The way they put it, a GRB would simply set the world ablaze – atmosphere and solid matter included. I only asked because I thought if it was small enough to inflict the damage it did, but did not bring about a world wide cataclysm, I thought it could be a possibility.
I’m not buying this theory:
If it was a fragment of the comet that skimmed past Earth, then someone, somewhere must have seen the comet in the days or weeks before or after the event as it moved along in it’s orbit.
Also, the comet should have had a tail, and that means debris. Where there any reports of meterors around the date of the explosion? Plus, that debris field would still exist, and we should be able to find it, along with corresponding meteor showers.
Finally, any comet that skimmed the Earth in 1908 may also be able to be tracked down, using mathematics and computer simulations. After some time, it could be narrowed down, if it’s real that is.
If these things can be documented, then the theory might hold some weight. Unfortunatley, it sounds like someone is trying to bait some funding, or get his name in the press.
I mentioned ‘mirror matter’ after reading of accounts in France, Jordan and China where meteors exploded in the lower atmosphere (relative) and produced a sonic boom(s) and creating an electromagnetic pulse hot enough to fry (turn to ash) all nearby vegetation yet not leaving a crater.
In other words, complete matter to energy conversion. That would be fission right?
Q: What fissionable elements might otherwise explain the energy levels required for gamma ray production?
Fused glasses found in the deserts of Africa and Australia may prove to be remnants of mirror matter annilation events… or at least some other atmospheric fission event.
Wow, that was some explosion. Did the flying spagetti monster drop a “bomb” from space to punish the woodland creatures of the Russian frontier? We will miss them.
After reading through the article, I just feel that I need more info. Can you share some resources please?