Honey, I Lost the Crater!

By Dr. John C. (“Jack”) Adler, as told to Bill DeSmedt

Howdy, folks, and welcome to my Soapbox Seminar Series all about the Tunguska Event of 1908.

Just what the heck is the Tunguska Event, you ask?

Well, thereby hangs a tale …

* * *

At seven-fourteen local time on the morning of June 30, 1908, the Russian settlers and native Evenki tribesmen living out in the sparsely populated Tunguska region of the Central Siberian plateau were treated to the grandaddy of all rude awakenings. Something — nobody could be quite sure what — blazed a bright blue trail across the early morning sky and exploded over the basin of the Stony Tunguska River with a boom! that could be heard a thousand miles away.

The way eyewitness Semyon Borisovich Semyonov put it, it was as if “Suddenly the sky was split in two, and high above the forest the whole north of the sky was covered with fire.”[Kulik 1927]

Depending on how you reckon it, the force of that explosion was anywhere from two to forty megatons of TNT — that’s anywhere from a hundred to two thousand times bigger than the atomic bomb that leveled Hiroshima. It toppled ancient stands of virgin Siberian forest across an area the size of metropolitan Denver. Its shockwave traveled twice — that’s twice, folks — around the globe, showing up on barographs in Potsdam, London, Washington DC, and Djakarta Indonesia. The glow of sunlight scattering off the explosion’s high-altitude debris lit the night skies over north Europe for the next month — lit them so brightly you could read the fine print in a newspaper at midnight.

If whatever it was hadn’t chanced to wreak its devastation in one of the most desolate spots on the face of the earth, if it had instead occurred five hours later, the earth’s rotation would have shifted the impact zone to the outskirts of populous St. Petersburg, and the death toll would have risen into the hundreds of thousands.

As it was, all it left was two thousand square miles of smoking wasteland, and one enduring mystery …

What caused it?

Because, from that day back in mid-1908, down to this one over a century later, nobody’s succeeded in coming up with a knock-down explanation for what’s become known as the “Tunguska Event.”

But, as we’ll see, that’s not for lack of trying.

* * *

This series of informal talks — I’ve taken to calling them “Soapbox Seminars,” because, like the soapbox speakers in at Speakers’ Corner in London’s Hyde Park, I do tend to get a little, uh, strident at times — is going to focus on one of those attempts at a Tunguska Event explanation, the one I call the “Vurdalak Conjecture” (Vurdalak being the Russian word for “vampire”).

Put simply, this conjecture holds that a submicroscopic primordial black hole might have been the Tunguska culprit.

But before we get to Vurdalak, we’re going to have to review the current state of Tunguska studies as a whole, in a seminar I call —

Honey, I Lost the Crater!

Let’s start with something that Tom Gehrels, the principal investigator for Operation Spacewatch, wrote in Scientific American about twenty-five years back:

The identity of the Tunguska object inspired a lot of nonsensical speculation for decades, and some highly imaginative suggestions were made, including that it was a mini-black hole or an alien spacecraft. Scientists, however, have always understood that it was a comet or asteroid.

Got to confess, I just love that quote. Because Tom’s a hundred percent right: Scientists — real scientists, like he almost says — have always understood that the Tunguska object had to be a comet or an asteroid.

Had to be.

They just didn’t know which.

Seems sort of strange, though, doesn’t it? Dozens of expeditions over the years, more trees consumed in publishing papers about the disaster than in the disaster itself, a new “solution,” so called, coming down the pike seems like every other year or so —

You’d think in over a century’s time they could work out something simple, like: Was it a comet or a meteorite?

Well, you’ve got to sympathize: Tunguska’s a hard place to get to, even now, more than a hundred years after the Event. And once you get there, there’s nothing big and obvious to look at: no crater, no fragments, nothing that jumps out at you and hollers “Hey, I’m a meteorite!” or maybe “It’s the comet, stupid!”

Then, too, there’s only three or four months out of the year you can get any useful work done on site, and that’s in the middle of summer, when the whole place is infested with skeeters so big and mean the Russians call them “flying alligators.” They’ll bite you right through a protective rubber glove. I mean those’re some serious insects!

No, Mother Nature sure hasn’t made it easy for folks to investigate this particular mystery of hers.

But that’s not what’s really keeping scientists from coming up with a definitive answer to the riddle. No, their real problem is — other scientists. Seems like every time some researcher’s ready to declare victory for one theory or another, a researcher for the other side pops up and shoots his idea full of holes.

It’s gotten to where folks who ought to be out looking for new evidence are spending half their time trying to explain away the evidence some other folks have already found.

Now, there’s no way I can give you all the back-and-forth on this. Even considering it took almost twenty years to get the first scientific expeditions in there, that still adds up to nine or so decades of theorizing and counter-theorizing.

But maybe I can give you the flavor of it quick enough.

* * *

At first, relatively few scientists even knew about the Tunguska Event. And those that did assumed it must’ve been a giant meteorite that had crashed that summer morning in the backwoods of Central Siberia. That hypothesis went unchallenged for nearly two decades — which was how long it took to get an expedition in on the site.

Not that the delay wasn’t understandable: Russia had other things on its mind in the years following the 1908 Event, after all: Things like World War One and the Bolshevik Revolutions — not to mention a Russian Civil War and famine and general socio-economic upheaval thrown in for good measure.

Oh, there were a few attempts to get through to the Tunguska basin in those early years, but they all came to nothing in the end. In part because the native Evenki guides refused to enter the area. They seemed to think it was under a curse.

Wonder why.

Then, one fine spring day in 1927, everybody’s favorite theory — a meteorite impact — went up in smoke. Because that was the day when mineralogist Leonid Alekseyevich Kulik finally reached the Event’s ground zero, a place Kulik called “The Cauldron.”

Once he got there, he knew he’d come to the right place: All around the Cauldron, far as the eye could see and beyond, the ancient forests of the taiga had been scorched and flattened by the blast. Something like forty million trees had been toppled like matchsticks in all directions, forming a radial “throw-down” pattern in the shape of a gigantic target, with the supposed impact site at the bulls-eye.

But, in reaching ground zero at last, Kulik had dealt a death blow to the meteorite hypothesis he himself had championed.

Because there was no crater.

Leonid Alekseyevich was expecting to see a hole the size of the Grand Canyon, but all he found was what he called a “telegraph-pole forest” — a grove of pine trees stripped bare of bark and branches, standing upright in the middle of a much larger expanse of radial treefall. That, plus a few waterfilled depressions that might have been mini-craters, but turned out to be just plain old sinkholes.

(Then, of course, not far away there’s Lake Cheko, which some folks from the University of Bologna have recently been claiming as the long-lost “Tunguska Impact Crater.” Makes for a good story, too, except for one thing — namely, there’s eyewitness testimony for that lake having already been there way before the 1908 Event. We’ll devote a whole separate seminar to that one later on. No sense getting ahead of ourselves right now.)

For now, let’s just assume that, whatever caused the Tunguska catastrophe, it had not been a conventional meteorite impact.

Kulik would return to Tunguska three times over the next twelve years, never quite giving up hope — but never finding that elusive crater either.

When he died in 1942 in a Nazi prisoner-of-war camp, the riddle seemed no closer to solution than when he’d first laid eyes on the “Cauldron” a decade and a half earlier.

But, in a way, the Second World War that took Kulik’s life also furnished one of the first clues as to what had happened in Tunguska long ago.

But that’s a story for next time.


[Kulik 1927] L[eonid] A[lekseyevich] Kulik, “The Problem of the Impact Area of the Tunguska Meteorite of 1908,” Doklady Akademiya Nauk SSSR (A), No. 23, 1927, pp. 399-402. (an English translation by John W. Atwell may be found in Appendix B of John Baxter and Thomas Atkins, The Fire Came By: The Riddle of the Great Siberian Explosion, Doubleday, 1976, pp. 155-156.)

[Gehrels 1996] Tom Gehrels, “Collisions with Comets and Asteroids,” Scientific American, March 1996, pp. 54-59.