Vladimir Rubtsov: The Tunguska Mystery. 318 p. Springer 2009.
Review © Norman Sperling, February 22, 2013
The explosion of a large meteor above Chelyabinsk, on the same day as asteroid 2012 DA14 buzzed Earth, has brought back the riddle of the Tunguska event.
In 1908, far to the east of the Ural Mountains, over the Podkamennaya Tunguska River in central Siberia, something - an icy, rocky asteroid or comet? - slammed into Earth's atmosphere, exploded in the air, flattened a forest, and triggered unusually bright and colorful skies over much of the world for many days.
The site is terribly remote. Communication and transportation were primitive in the terminal times of the tsarist empire. After World War I, the new Soviet regime clamped down on communications with non-Communists.
Very little news about the Tunguska explosion leaked out through the Iron Curtain. A few Soviet scientists explored, but hardly any of their data reached the West. Eyewitness reports were gathered, but we didn't see them. Important scientists declared solutions, but we only heard their answers, not their supporting data.
The absence of scientific data opened infinite possibilities for speculation. Creative minds responded by suggesting a colorful variety of explanations. Some of those caught the public imagination.
Unbeknownst to the West, much the same was happening in the Soviet Union. By selecting favorite reports, theorists put together plausible narratives which hung together only as long as all other data were ignored.
This grated on a lot of Soviet scientists. After Stalin died in 1953, Khrushchev loosened the repression. Professional and amateur scientists responded creatively by founding the Independent Tunguska Exploration Group in 1958. These days the fashionable name for this centuries-old practice is "Citizen Science".
Investigators gathered information to plug holes in previous work. We hardly ever heard their results. In this book, an ITEG stalwart describes their research, findings, and speculations.
The story is FAR more complex than I had imagined. Exploration found a great deal more information than I had ever heard of, much of it scientifically strong. Practically all of it appears to contradict some theory or other. Several fairly strong solutions have been proposed, accounting for large portions of the observations. No solution, however, has yet accounted for all the credible data.
So this book is a superb example of exploratory science, and a superb example of a scientist who understands how much he doesn’t understand.
The most frequent suggestions are comets or meteoroids or asteroids. One huge problem is that our concepts of these have changed often, and radically, over the last 100 years, so the proposal means different things to different people at different times. Recent understandings relate comets to primitive chondrite meteoroids, which are extremely similar to asteroid types C, P, D, and K. Those meteoroids are probably chips of those asteroids. If they have surface ice, they appear as "comets". The Sun can vaporize surface ice while leaving ice inside.
Yet many details, from the exact pattern of the fallen trees, to eyewitnesses describing one object approaching from the south while a second one came from the east, to chemical traces (ytterbium!), don't seem to concur.
The suggestion that appears to satisfy the most data - still not all - posits 2 huge and powerful spacecraft, both turning to converge at the explosion site, and only one continuing westward from there. Science fiction fans like this scenario a lot better than most scientists do, but it satisfies more data than any other.
The comet concept satisfies the second-greatest quantity of data.
Now that this book has taught me a great deal more about Tunguska science, I am no longer confident about any one explanation. Rubtsov is right: we don't know enough. Previous such cases include:
• discovering the constancy of the speed of light, before Relativity;
• Auguste Comte's declaration that the composition of remote stars must remain forever unknown, before spectroscopy;
• noticing fundamental parallels in living things, like backbones, before Evolution.
Enjoy this book for its rich scientific and historical narrative, its scientific rigor, and its logical structure. The book is well written, well edited, and well produced. There's just enough Russian syntax to suggest local flavor. But if you want The Answer to what hit Tunguska, it's not here, nor anywhere else. Yet. Check back later.