Digression I, Part 1: The Tunguska Follies

Well, It's Groundhog Day — Again(?)

There's one less enduring mystery in the world tonight, folks. To hear those crack researchers at the University of Bologna, Italy tell it, they've gone and solved the riddle of the Tunguska Event — again(?).

Remember that old definition of an honest politician — one who, once bought, stays bought? Tunguska's like the backwards of that: just because it's been solved, doesn't mean it'll stay solved. The last time Bologna U solved this particular mystery was back in 2001 (BBC News Online, "Mystery Space Blast 'Solved,'" 30 October 2001). That time, Luigi Foschini and his team decided that the impactor must have fragmented in the atmosphere so totally that it vaporized altogether "with only the shock wave reaching the ground."

But no, wait, that can't be right. Because now Luca Gasparini, Giuseppe Longo, and their team are telling us they've up and found the crater! (Must not have evaporated totally, dude!)

It's a slow news week, I guess. How else to explain the column inches (or electronic equivalent thereof) being lavished on this announcement? Here are what I take to be the principal URLs:

BBC Online/Science

Space.com

AOL News

(Parenthetically, I might point out that you know you're in trouble when AOL.com — the "all Paris Hilton, all the time" newsfeed — picks up your story and runs with it.)

Be all that as it may, let's put this latest solution under the microscope and try to figure out whether our friends from Bologna are or are not full of, uh, bologna.

So, What's Being Claimed?

Just this: that Lake Cheko, a small body of water situated about five miles northwest of the epicenter of the explosion, is in fact a crater formed at the time of the Event. Only subsequently did it fill with water, giving it the lake-like appearance it presents to us today.

If true, this would indeed be — as the Space.com article puts it — the long-sought "smoking gun" for the Tunguska-as-meteor-impact theory. But is it true?

Read down a little further in any of the published reports and you find that this new solution is based upon (a) the generally round shape of the lake, (b) some computer studies that indicate a conical shape to the lake bottom, and (c) the Bologna team's seismograph readings of "an unusual feature about 10 m[eters] down which could either be compacted lake sediments or a buried fragment of space rock."

"When we looked at the bottom of the lake, we measured seismic waves reflecting off of something," as Giuseppe Longo, a physicist at the University of Bologna in Italy and co-author of the study, told Space.com "Nobody has found this before. We can only explain that and the shape of the lake as a low-velocity impact crater."

Okay, so the lake is really, really round (actually, it's elliptical, which doesn't quite fit the meteorite-impact model, but never mind), and conical, and there's something down there. I don't know about you, but that sure sounds like an ironclad case to me — not!

As Professor Longo admitted to BBC Online/Science. "We have no positive proof this is an impact crater, but we were able to exclude some other hypotheses, and this led us to our conclusion."

So, let me see if I get this ... you have no proof, but this might be true, so you conclude it is true. That about sum it up?

Whenever I encounter reasoning like that, I'm reminded of Carl Sagan's hilarious standup routine from the Cosmos Venus episode. In it, Carl parodies the thought processes of the early Venusologists along the following lines: "We can't see the surface of Venus at all; the planet's completely covered in cloud. Clouds mean rain, so lots of moisture, then. It's probably hot, humid, swampy — maybe there's even dinosaurs." Carl then sums it up: "Observation: Can't see a thing. Conclusion: Dinosaurs!"

So, the real question is: are our friends from Bologna seeing brontosauri in amongst the cumulo-nimbus? Or, to put a finer point on it: is that a smoking gun in Professor Longo's pocket, or is he just happy to see us?

Well, he's clearly happy to see us. The hundredth anniversary of the Event is now only a year away — and "Longo's team plans to return to Lake Cheko next summer," as we read in AOL News — so the clock is ticking. These centennial expeditions don't fund themselves, you know. A little publicity never hurts when it comes to filling those travel-allowance coffers.

(On that score, there's the little matter of the timing of the announcement. All the in situ research for the "Crater Cheko" solution was done by the University of Bologna team back in 1999. Why did they sit on it for eight years? Especially given that the Foschini team published its results from the same 1999 expedition within two years of returning home? Could it be that the concept had been consigned to a desk drawer, and was only pulled out and dusted off when it came time to pass the hat again?).

Deja Vu All Over Again

I guess what really irks me about the University of Bologna solution-mill is how little attention its researchers seem to have paid to the body of scientific and documentary evidence already amassed on the topic of Tunguska. You'd think they'd know better by now, especially since an ignorance of the relevant literature was one of the charges famously leveled against Albert A. Jackson IV and Michael P. Ryan Jr. when they proposed their Tunguska-as-black-hole-impact conjecture back in 1973 (for more on that, see the Vurdalak Conjecture).

Nonetheless, such a lack of familiarity with prior work seems to be operating here as well. For instance, I can't find any reference in the published reports to the fact that the whole "Crater Cheko" hypothesis was raised nearly half a century ago by Russian researcher V. Koshelev. Nor that said hypothesis was tested and found wanting at the time.

Here's what K P Florensky wrote in his article on "Preliminary results from the 1961 combined Tunguska meteorite expedition" (Meteoritica, vol XXIII, 1963 [italics mine]):

Silt specimens from Lake Cheko and the lake in the bend of the River in the west morass were collected for subsequent stratigraphic study (P.N. Paley et al.) with a grab dredge and a swamp drill designed by N.I. P'yavchenko. The various samplings from the bottom of Lake Cheko (P'yavchenko, Kozlovskaya) revealed extensive development of silt up to 7 meters deep, indicating an ancient origin for the lake (tentatively estimated at 5,000 to 10,000 years), thus completely contradicting the hypothesis of the formation of the lake as a result of the Tunguska meteorite fall.

Not to be outdone, a bevy of scientists — including NASA's David Morrison, Gareth Collins at Imperial College, London, and Benny Peiser, from Liverpool's John Moores University — have all joined in to pick other holes in the solution, ranging from a too-shallow angle of entry, to the absence of a "lip" of ejecta around the rim of the supposed crater, to the very slow impact speed required to make any of this work.

It's actually interesting that the published articles contain more than their usual fair-and-balanced quota of such critical commentary on the Crater Cheko concept. It's almost as though the newsfeeds are determined not to be caught napping by the Bologna solution-mongers yet again. But no matter how many counterarguments are mounted, the bottom line is still this: With enough finetuning, even the most implausible scenario can be made to work, or seem to. I immodestly cite the "solution" to the Tunguska Event contained in my own novel Singularity as a case in point.

No, let's face it: if you really wanted to disprove the Gasparini-Longo hypothesis, what you'd have to do is one thing and one thing only — simply show that Lake Cheko was there before June 30, 1908.

Because if that body of water truly predated the Tunguska Event, then it can't be a waterlogged crater caused by that Event. Q.E.D.

The Other Smoking Gun

Figuring out whether or not Cheko was there before the impact sure sounds easy enough. I mean, it's a whole lake, right? Over five hundred meters long and maybe fifty deep. Kind of hard to miss, you'd think.

On the other hand, it's located in the Stony Tunguska River Basin — three hundred thousand square miles of impenetrable wilderness, inhabited in 1908 by fewer than thirty thousand souls. That's ten square miles of trackless desolation for every man, woman, and child. Maybe not so hard to miss, then.

At the same time, Gasparini and Longo are quick to point out that Lake Cheko does not appear on any maps before 1929. One might counter by asking "Maps? What maps?" The Stony Tunguska watershed was hardly a hotbed of cartographic activity in the first decades of the last century, and this tiny, nondescript geographic feature is a veritable needle in a haystack. And that's setting aside the fact that the native Evenki shamans barred entry to the impact zone for twenty years after the Event, believing it to be accursed.

No, if there's any evidence, one way or the other, for the pre-existence of Lake Cheko, it'd have to be in eyewitness accounts.

And here's where we strike pay dirt (or perhaps, in keeping with the subject matter, I should say lake bottom?).

Because, as luck would have it, a catalogue of Tunguska eyewitness accounts not only exists, but, through the good offices of Andrea Ol'khovatov, has been made available on the Internet right here. The catalogue, entitled "Testimony of the Eyewitnesses to the Tunguska Impact," was compiled back in 1981 for the All-Union (now All-Russian) Institute for Scientific and Technical Information (VINITI) by the grand old man of Soviet/Russian Tunguska studies, Academician Nikolai Vladimirovich Vasil'ev himself. It gathers together into one document both contemporary newspaper reports and the testimony of all the witnesses to the Event recorded by a variety of researchers from 1921 through the 1970s. The sole drawback is that, to date, the bulk of its materials are available only in Russian (though I've translated a few of the more interesting bits for the "Vurdalak Conjecture" website here).

So, does this document have anything at all to say about Lake Cheko? More particularly, about whether it was there before the impact or not?

Let's start with what seems to be the earliest recorded account making any sort of mention of a lake: the report of Ilya Potapovich Popov (more commonly referred to by his Evenki name Lyuchetkan), taken in 1924 by geologist S. V. Obruchev (VINITI, p. 23/14). There we find Lyuchetkan saying [italics mine], "In that place where the stone fell, there is a pit, and from it some creeks [running] into the Chambu. There is a lake nearby, but it existed before the fall of the meteorite."

Lyuchetkan seems to be about as close to an unimpeachable witness as we're likely to find in these annals: He lived close to the impact site (his brother, who lived even closer, had his hut blown high into the sky "like a bird" from the blast, and became so fear-stricken by the whole experience that he was unable to speak for several years thereafter). As a herder and hunter, Lyuchetkan could be expected to know the surrounding area as well as anyone. And his veracity is independently attested by one N. N. Kartashov, who stated to geologist A. N. Sobolev that "it is impossible not to believe Ilya Potapovich's story" (VINITI, page 13/8).

So here we have a by-all-accounts reliable source for the contention that the existence of a lake antedated the Tunguska Event. This testimony raises two questions, however: (1) is the lake Lyuchetkan talks about our lake — Lake Cheko? and (2) why was he so adamant about it being there before the Event, in the first place?

To take the second question first, it seems likely that Lyuchetkan was being so insistent on the prior presence of a lake because he was trying to lay to rest other stories then making the rounds (which his interviewer may in fact have asked him about). It is the case that, at several points in the VINITI catalogue, unattributed rumors are cited that a lake had formed after the impact, rumors which are then discounted by the very same source reporting them (see VINITI, pages 30/18, 34/21, 161/93).

But was the lake Lyuchetkan spoke of the one we're looking for? There are two other accounts in the catalogue that strongly suggest it was.

The first, by Lavrentii Vasil'yevich Dzhenkoul, was collected in 1960. Dzhenkoul was only four years old at the time of the 1908 blast, but he recounted the stories passed down to him by his father and uncle (VINITI, page 95/56 [italics mine]):

In that place the seven rich Dzhenkoul brothers in those days pastured a reindeer herd of 600-700 head. The brothers were rich. On that day, Father went to meet the reindeer on the Ilimpo [river] (in the north). The herd was pastured between the Kimchu river and the Polnoty (Churgim) river. On the upper reaches of the Polnoty river there was a storehouse. There was a second storehouse at the mouth of the Cheko. There, where the first storehouse was (on the Polnoty-Churgim), everything was burnt up. Of that storehouse there remained only ashes. The storehouse at the mouth of the Cheko was thrown over (carried away) by a whirlwind. At the headwaters of the Khushmo [river] their herd was burned, the reindeer were burnt up, only ashes remained. At the mouth of the Cheko, the reindeer lay curled up, but they didn't burn (they had been stunned and they died).

Three mentions of the "mouth" of the Cheko (i.e., the point at which the lake flows out into a stream) makes it pretty definite that the younger Dzhenkoul had not misremembered that aspect of his hand-me-down tale. And the context makes clear that the second storehouse must have been located at the mouth of the Cheko before the Event, since the blast itself swept the structure away. Which, in turn, means the Cheko itself was there too.

Finally, we have the testimony of Vasilii Nikolaevich Dmitriev taken in 1960 by G. B. Kolobkova (VINITI, page 104/61):

The road from Strelka to Vanavara passed through Lake Cheko, From Ilimpei you could go to Strelka. There was no trading post there at that time, but the road went through. Further on toward Vanavara, the road went through [across?] Lake Cheko.

It is just an incidental mention, also at second-hand, but the repetition rules out a mistake in transmission, and the context strongly implies that Lake Cheko was a well-known waypoint among the hunters and trappers who traveled that forest road prior to the Event. (After the Event, such landmarks would have been of no use, since the area had become, to all intents and purposes, closed to traffic.)

Would any of this stand up in court? Almost certainly not. It's all hearsay evidence, after all — stories passed on from father to son, from friend to friend, or at best from subject to interviewer. On the other hand, passages from these same sources were deemed reliable enough to have been used in cobbling together the earlier Bologna solution to the Tunguska riddle. In the 2001 BBC Online article, Luigi Foschini stresses that his team's methodology combined original seismic and survey research with what he touted as "unpublished eye-witness accounts that have never been translated from the Russian."

All I can say is: maybe Gasparini and Longo should have gone back to Foschini's unpublished sources for a re-look this time around, because those selfsame eyewitness accounts show their "crater" was there AS A LAKE well before the Tunguska Event.

Much Ado About ...

Well, if you can read all that and still think this latest solution's going to fly, I've got some lovely beachfront property in Arizona I'd like to sell you. Nonetheless, even the least prepossessing concepts can bear lessons in their train, and such is the case here.

For one thing, I find it fascinating how quickly the total-vaporization Tunguska airburst hypothesis has been backburnered now that the meteorightists smell crater. Could it be that, in their heart of hearts, they were never really all that comfortable with total volatilization of an object the size of a football field?

Another is: we seem to have reached the point where we've begun repeating ourselves — proposing solutions that have been tried before. And forgetting ourselves — not even rechecking the same sources our own institutional colleagues are citing.

The meteorite/cometary impact theorists have had a virtual stranglehold on Tunguska studies ever since Kulik's first expeditions back in the 1920s, with nothing much to show for it so far. Maybe someday we'll look back on the tunnel vision afflicting the past eighty years of Tunguska research as yet another case of the sociology of science run amok and down a blind alley, as Lee Smolin argues vis-a-vis string theory in his recent The Trouble with Physics.

A wise man once pointed out that the surest sign of madness is when you keep on doing the same thing over and over and yet expect a different result. Maybe it's time to end the madness and crack open the door to some alternative explanations again.