100 years ago today: KABLAM!!!!!

By Phil Plait | June 30, 2008 12:02 am

Two notes: Commenting on the blog will be turned off after 14:00 UT today for a major blog upgrade. Also, an article is in USA Today, um, today, about the topic of this post, and I’m quoted in it.

100 years ago today, a small chunk of rock or possibly ice was lazily making its way across the inner solar system when a large, blue-green planet got in its way. Traveling roughly westward, it entered the Earth’s atmosphere moving at tens of thousands kilometers per hour. Compressed and battered by tremendous forces, the object got about 5 – 10 kilometers from the ground before it succumbed, exploding like a gigantic multi-megaton bomb.

The air blast flattened trees for hundreds of square kilometers. The ground shook, witnesses felt the hellish heat from kilometers away, and the shock wave circled the world. It happened over the remote Podkammenaya Tungus river, a swampy region in Russia; had it happened over Moscow a million people might have died within minutes.

Now known as the Tunguska Event, it stands today as a shocking reminder that we live in a cosmic shooting gallery, and the Earth sits in the crosshairs of many objects.

The event has been studied extensively. An expedition to the region revealed no crater, to the surprise of those early 20th century scientists. This was the first clue that it was an air blast. No debris has ever been conclusively identified as extraterrestrial, leading to some debate over whether it was a rocky asteroid or an icy bit of comet. Some asteroids are like rubble piles, pulverized by impacts as they orbit the Sun; these are fragile objects that would more easily explode in the air. I’ve often wondered if this would explain the situation.

The past century has seen many changes in the way we do astronomy, and how we hunt for dangerous rocks. Automated surveys scan the heavens, tirelessly looking out for bullets with our name on them. Astronomers model the impactors and impacts, looking for ways to understand them better. Scientists propose physically going to asteroids with robotic and manned missions, to get far better data on them.

All of this is more than just scientific curiosity: our survival as a species may depend on it. And that’s no exaggeration.

So I congratulate those who study these killers, and who look to our future — and here I will call out my personal friend Dan Durda who is very concerned indeed, and has devoted his career to them. I applaud the B612 Foundation, which is devoted to mitigating this danger. And I especially stand up and point to Congress — including my own Representative Mark Udall — which has the foresight to mandate that NASA look into the dangers from the Near Earth Asteroid Apophis. I wrote about this extensively in my book Death from the Skies!, and I learned far more than I wanted to about what happened over Tunguska. I’m very glad others are taking this threat seriously.

We’ve come a long way since that hot, muggy Russian morning on June 30, 1908. And let’s be clear: if another Tunguska-class object had its sights set on us, we wouldn’t know it until we, like those Russians, saw a flash of terrible light in our sky, felt the burning heat, and were knocked down by the blast.

The odds of it happening any time soon are low, very low. I don’t lose any sleep over it — I’m not worried, I’m concerned. But this anniversary is a sobering reminder that it can happen again, and it will, unless we do something about it.

Artwork credit: the fantastic space artist Don Davis. Used by permission.

Comments (44)

  1. Dave Hall

    The first I ever heard about the Tunguska Event was from a book I picked up in the mid 1970s called: “The Fire Came By.” I don’t recall the authors, but I remember Asimov wrote an inrotduction.

    By the end of the book I was not feeling very charitable towards Dr A. The book claimed the explosion was caused by a–get this– nuclear powered alien spacecraft!

    I was fairly recently out of high school and very poorly educated in matters scientific, but it was obvous to me that the book was a crock of bull. And there was Asimov lending an air of legitimacy to it. It took quite a while before I ever trusted anything Asimov had to say in his non-fiction works.

    I was, however, spurred on to find out more about the event and thus furthered my self education in astronomy and physics. I still don’t know much, but I have learned how to learn, and I have developed a fairly healthy level of scepticism.

    So an event 100 years ago in Siberia had an impact on me 30plus years ago–an impact that has shaped my life. Coincidence? Art Bell, George Noory, Richard Hoagland and the rest of the Coast-to Coasters may disagree but– Yeah, its a coincidence.

  2. Quiet Desperation

    It was Tesla!!!!!!!

  3. Gadren

    It’s amazing, not just to consider what it could have done had it hit a major city, but also to realize that it could very well have. If the collision had been delayed by 4 hours 47 minutes, it would have flattened St. Petersburg (the capital of then-Imperial Russia). More than just a hypothetical transplantation of a disaster, it’s a stunning reminder of what could have happened had the “clockwork” of the various orbits been slightly different.

  4. There was a fascinating article in SciAm recently about Tunguska. Seems there may actually be a crater after all (now a lake) and a team is due to visit (next year I think) and investigate whether there is a fragment beneath it (it showed up on Radar, from what I remember of reading the article).

  5. Philip

    an article on the hypothesis that a piece of the bolide actually left a crater, in German only, but some self explanatory pictures.
    http://tinyurl.com/4oqjjw
    Authors:Luca Gasperini, Enrico Bonatti und Giuseppe Longo

  6. Reed

    Canada is also recently announced a NEO observation mission, recycling much of the technology of their highly successful satellite MOST.

  7. Jeff Fite

    “The dinosaurs are dead because they didn’t have a space program.”
    –Larry Niven

  8. Geophysicist

    Jeff says – “The dinosaurs are dead because they didn’t have a space program.”

    I say yes they did, where do you think they all went?

  9. Electro

    Thanks Materia7,

    I’ve seen those images about a hundred times but this is the first in about ten years.

    I gotta say though, with no scientific basis, something about those pics doesnt seem quite right.

    It’s not that I doubt their veracity, its just that the entire scene seems…odd.

    Maybe, its because they’re the only images I’ve ever seen of recent extraterrestrial impact ( or nearly so ).

    What was the interval between the event and the photographs?

    I think what it might be is that I’m looking at miles of flattened adult trees shorn clean off at both ends and stripped of bark with no exposed root balls and in the midst of untouched saplings.

  10. tacitus

    I already used this comment of mine on another blog, but it bears repeating here…

    It’s worth remembering how far we’ve come in 100 years since Tunguska:

    In 1908, at the time of the strike, we knew of about 665 asteroids, all but four discovered in the previous 100 years. In 2008 we’ve just passed 400,000 mark for observed asteroids and comets.

    In 1908 we knew of just one near-Earth asteroid — Eros. In 2008 over 5400 have been discovered, plus about 65 near-Earth comets.

    On the eve of Tunguska, we hadn’t a clue about the danger lurking above us. Today we’re well on the way to understanding precisely what the risks are especially when it comes to the largest, most deadly, asteroids out there.

    Yes, the numbers are scary, and there is plenty more work to do, but thanks to the tremendous efforts of a relative few dedicated astronomers and scientists, Earth will be a much safer place to be in the years ahead (concerning NEOs, anyway).

  11. tacitus

    One thing that does seem rather remarkable is how people can be so blasé about asteroid/comet strikes and yet get so worked up about the possibility of a Planet X crashing into us, or some mythical mega-solar outburst consuming the Earth.

    They seem to implicitly trust astronomers when say that there are no immediate threats from asteroids (that we know of) and yet when it comes to debunking Planet X, they pour scorn on the astronomers’ disbelief and debunkings.

    I guess, as is always the case with pseudoscience, reality just seems to become dull and uninteresting by comparison. Why get excited over a few lumps of ordinary rock when there’s a mysterious planet to track down?

    Cheapening the wonders of the Universe is an unforgivable crime of the pseudoscientists, not far behind that of demeaning the careers of real scientists who toil for years with little reward while they reap the spoils to churning out the nonsense that clogs up the shelves in bookstores.

  12. tacitus, good points. Look at how the issue of terrorism, which has cost the US on the order of a few thousand lives in the US, and not a lot more worldwide, commands so much attention, energy, and money. In Israel, they just deal with it the way that Americans deal with the risk with driving anywhere.

    And, similarly, god is given credit for great accomplishments and not mentioned when things go south.

    A prudent, rational reaction is to spend a minimal amount to make sure we’re properly aware of these rare but catastrophic threats, and to trust the scientists to tell everyone what is credible and what is crap. We’re trustworthy on that spectrum.

  13. Gary Ansorge

    I expect space industrialization and a functional space navy will have to go hand in hand, just to prevent some terrorist group from dropping rocks.

    Goody! Another excuse to expand milatary presence in space,,,

    GAry 7

  14. Christian Treczoks

    A few days ago we had a documentation about Tunguska on TV with some fun inserts between the chapters: with a mock 1950 sound quality fanfare and title, another (loony) theory was announced and shown as a short cartoon:

    “Tunguska Theory No. 73: A UFO that happened to visit earth back then started and sacrified itself by colliding with the meteor (both exploded in that accident). That is the reason that no-one so far found an impact crater or meteor core.”

    Has anyone out there a list of all those funny and ridiculus ideas on Tunguska floating around?

  15. Graham Cheesman

    Read the latest New Scientist for a range of theories on this event.

  16. quasidog

    Oh didn’t realize that happened on my B’day ;p

  17. Nigel Depledge

    Graham, that NS article really only discusses two theories – first, that it was a bolide, and that Lake Cheka is the crater (perhaps with fragments of the impactor buried beneath its sediment), and, second, that it was a geological event known as a Verneshot (a catastrophic ejection of gas, such as methane or CO2, released from rising magma).

    Curiously, the light in the sky from the event lingered for a long time – apparently, it was bright enough in London a day or two after the event to read a newspaper at night.

  18. Nigel Depledge

    Quasidog, happy 100th birthday!

  19. George Kopeliadis

    I bet it was the aliens. Just a warning… and the world leaders bowed in obidience…

  20. madge

    @ quasidog
    Happy 100th Birthday Buddy. You are looking good for your age!
    :)

  21. Donnie B.

    Science News had a feature article on the 100th anniversary of Tunguska in the last issue.

    They made a couple interesting points. First, the idea that Lake Cheko is the blast crater is pretty well refuted. There are photographs of that area taken in 1938 that show mature trees well over 30 years old, so there could have been no blast there in 1908. Also, the area around the lake shows no signs of an ejecta blanket.

    Secondly, there is at least one theory for the explosion that doesn’t involve extraterrestrial causes at all: formation of a kimberlite deposit, like those that bring diamonds to the surface. Such events are believed to release large volumes of methane, which could have resulted in a fuel-air explosion. That would explain the lack of a crater or any meteorite fragments.

    Even if that’s true, it doesn’t invalidate the idea that we should be alert for potential impactors. Whether Tunguska was a space rock or not, events of that scale are expected every 500 years or so. Even though it’s not “extinction scale”, a similar blast would not be healthy in a world full of nuclear weapons and itchy trigger fingers.

  22. Mang

    Not quite 100 Years ago today, almost 2 weeks left to go folks.

    Russia and Siberia in 1908 would have been using the old Julian Calendar common amongst the eastern Christian churches.

  23. bitemark

    I always wondered if it didn’t come from another planet.

    A far-away planet.

    A bug planet…

  24. bitemark

    Mangon 30 Jun 2008 at 6:01 am

    Not quite 100 Years ago today, almost 2 weeks left to go folks.

    Russia and Siberia in 1908 would have been using the old Julian Calendar common amongst the eastern Christian churches.

    Incorrect. It occurred on June 17 in the Julian calendar.

  25. Most mainstream media insists on referring to the Tunguska explosion as a “mystery,” and that is very annoying.

  26. L Ron Hubbub

    bitemark
    Mangon
    Not quite 100 Years ago today, almost 2 weeks left to go folks.

    Russia and Siberia in 1908 would have been using the old Julian Calendar common amongst the eastern Christian churches.

    Incorrect. It occurred on June 17 in the Julian calendar.

    You know, of course, that the Julian calendar was developed by putting the Gregorian calendar into a Veg-O-Matic.

    /obscure?

  27. Mang

    @bitemark – thank you. I double checked you are correct. (I thought I had checked that properly some time ago. I even wrote it down. Sorry for the confusion).

  28. Mang

    I new I’d written it down! It turns out Wikipedia was in error on the date prior to February 25th 2008.

  29. Mang

    grrr … knew even.

    @Ron are you trying to say the Julian calendar is fried?

  30. @Hubert Why is it annoying it’s called a mystery? The exact cause is a mystery right now and there are a number of competing plausible explanations (along with a horde with horde of implausible and outright crazy ones).

    Now if they’re using that uncertainty to promote the crazy explanations then that would be annoying.

  31. Hey, that’s funny– it occurred to me that the calendar change might affect the date! But then I assumed that this had been corrected in all the sources giving the date. Guess I was right. :-)

    I didn’t post pictures because of various reasons involving blog overhead and My Very Big News. I know I’m a tease, but this will all be clear very soon now.

  32. Nigel Depledge

    Donnie B – another reason why Lake Cheko is unlikely to be the crater is that it existed before 1908. I guess that’s pretty strong evidence, ;-).

  33. Tavi

    “But this anniversary is a sobering reminder that it can happen again, and it will, unless we do something about it.”

    That’s presuming that we CAN do something about it. But what if we cannot? As we explore how we might monitor and even affect an approaching NEO, we should give equal effort to developing a comprehensive Impact Event Contingency Plan; and we should do it right now rather than later. As you note, we may not have the luxury of time.

    I’ve thought about it often. WHAT exactly will we do, when we determine that an asteroid has our name on it and that there is nothing we can do to change its course? For example, what if Apophis does make the keyhole on that first pass in 2029? Will we evacuate vast regions of populations? Will we even know exactly whom to evacuate? How and to where will all of those people be evacuated? We will have seven years to react – will we use that time wisely, or will we wait until the last minute and then panic? Are we now waiting until that 2029 pass to even begin to consider how we should react?

    There are many questions that could actually be answered now; yet, as seems to be typical of those whom we enlist to address such issues, the response is slow and inadequate.

    I read and hear arguments for the need to more agressively address the issue of impact. Let’s hope that those putting forth the arguments are taken more seriously and with more expediency than what we have thus far seen.

  34. Farb

    (Phil, This is something that requires a planetary astronomer to calculate more exactly. I may be an amateur astronomer, but Bad Math is precisely WHY I’m an amateur! So Phil, I’m electing YOU [BTW, this is paraphrased from another post I made at another BBS, so to the well-travelled science surfer, I’m not plaigiarizing, just switching from a screen name I use in those happy controversy-free zones, where we get to discuss nothing but technology, techniques, and phenomena.]. Crunch the numbers and comment, please.)

    We often hear, in relation to Tunguska, that if it were delayed by x number of hours, it would have struck more densely populated regions, of course more disastrously.

    Well, I did some mental calculations. To be sure, an hour’s rotation of the Earth (about 1000 mph at the equator [7900mi x pi / 24h]) would have brought western Siberia to a point parallel with the Tunguska object’s original trajectory (2 hrs., Moscow; 3 hrs., Berlin; 4hrs., London [this is where my math breaks down–is it still ~1000mph at that latitude, or does it matter? Or should I rather calculate speed of longitudinal displacement?]), but then I considered the speed of Earth’s REVOLUTION.

    I was a little freaked out when I first realized, some years ago, that we are all constantly travelling faster than any astronaut has travelled relative to the Earth, our orbital speed around the Sun being about 65,000 mph (93,000,000mi x 2 x pi / 365.25d / 24h). And then reading ASTRONOMY magazine just today I learned that our solar system’s speed around the galactic center is about ten times that!

    (Now there’s a cute subplot for a time-travel story. Too often has the intrepid time-traveller pushed “the button,” and miraculously re-appeared at exactly the same relative physical location in a different time, rather than empty space hundreds of billions of miles away! [Well, admittedly, the very acronym T.A.R.D.I.S. accounts for this, but there don’t seem many other examples. Oh, well. Nothing in the universe is faster than the Speed of Plot, by definition.])

    Anyway, the Earth itself would have moved tens of thousands of miles in the intervening time, assuming the Tunguska meteor was somehow delayed. Indeed, by the time Earth’s rotation would have brought western Europe around, the meteor’s original trajectory would have been at the distance of the Moon’s orbit!

    Even as little difference as fifteen minutes means the meteor would have missed by as much as 99942 Apophis is scheduled to miss on 13/4/2029, and no one would ever have known (and so the unanswerable follow-up question is: how many times have we been missed in the past by so little?).

    But what if it had struck fifteen SECONDS later (I have a student who was born in Novosibirsk; we talked about this very subject this spring.), or a minute, two, three, or four? Then the impact zone would have shifted to the west by the speed of the Earth’s revolution, rather than its rotation (although by 4min., there seems a possiblity it may have struck the atmosphere at such a shallow angle that it would have skipped).

    These differences seem more in line with what gravitational perturbations might reasonably be expected to produce, and seen in this light, the narrowness of humanity’s escape seems all the more troubling. What do you think?

  35. Mask

    @Farb: The asteroid is moving relative to the sun, as are we, it’s not floating free where our speed around the galactic center would matter. Its being dragged along for that ride as well.

  36. Farb

    If Tunguska was a Beta Taurid, then the Earth would have been moving through the meteor stream (because of intersecting orbits). Sure, motion relative to the galactic center would not factor here at all, but meteors in the stream would themselves move in highly elliptical orbits (essentially fixed) around the Sun (assuming the Beta Taurid stream still “echoes” the orbit of Comet Encke), and the Earth’s duration of time “in the bullseye” would have been a matter of minutes, not hours.

    I submit that the primary factor affecting a different location for the impact, assuming a gravitational perturbation delaying Tunguska’s arrival, would have been determined by the Earth’s revolution in its orbit around the Sun, not its axial rotation. The practical upshot of this is that preventing a dangerous impact would be a matter of altering the impactor’s motion in its orbit just enough that it would not intersect the Earth moving in its own orbit.

    Seen in this light, the problem is more like managing air-traffic control (albeit from one of the aircraft). Once methods are determined for deflecting objects (and it seems several will be necessary, owing to the differing natures of asteroid and comet types), then the only difficult task will be to monitor the inner Solar System closely enough to catch rogues. Of course this argues for better asteroid study, as well as more mathematicians.

  37. Jerry W Barrington

    Tavi: Regarding Apophis…
    It will take politicians to do *anything* about such a potential impact. Consider the time scale, 17 years, then 7 more years. Modern politicians simply don’t operate on that timescale. It’s too far beyond the next election or 2.

  38. Somebody ought to write a book about this kind of stuff.

  39. And, by the way, Will Wheaton posted this post on his G+ page, so there you go!

  40. Renee

    There is a book by Bill DeSmedt called “Singularity” (http://www.billdesmedt.com) which puts a bit of a twist on the old Jackson/Ryan hypothesis, which posited that the Tunguska impactor was actually a primordial micro-black hole. It is a good thriller with secret agents, ex-KGB spies, and the whole “plot to take over the world” thing going on. Of course J/R has been discredited mainly due to the lack of an exit event in the north Atlantic ocean, but in the book the micro-hole was also a monopole, meaning it had only one magnetic charge, which greatly changes the game for the theory that the impactor was something other than a comet or a meteor. Primordial black monopoles are hypothetical objects that could certainly exist if the String Theory explanation of cosmic genesis (or something like it) is correct. I won’t ruin the story by explaining any further, but it is a great read and actual physicists like Kip Thorne and Jaccob Bekenstein have endorsed it for its scientific accuracy. There’s actually a free full audiobook version on podiobooks.com that is read by the author as well (http://www.podiobooks.com/podiobooks/book.php?ID=61). Additionally, there are a series of short seminars called “Dr. Jack’s Soapbox Seminars” that explain the real science behind the modified theory of black hole-as-impactor. They do a pretty darn good job of explaining black hole physics, debunking things like the Lake Checko crater theory, and pointing out some tantalizing details that lend some doubt to both the comet and asteroid theories at http://www.vurdalak.com/.

    There’s no doubt that *something* happened in the stony Tunguska river basin in the early morning hours of June 30, 1908, and based on the areal phenomena observed by Evenks witnesses in the area it was most likely some non-terrestrial object impacting the Earth, but the brutal truth is that after 104 years we have yet to discover any “nail in the coffin” evidence that conclusively identifies what that object was.

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