Was it a Flashback to Extinction or an Omen—The Tunguska Event

 

An artist rendition of what Siberian natives saw in the sky before the explosion that has come to be known as the Tunguska Event.

It was the largest impact event on or near Earth in recorded history.  An explosion three to six miles above the surface of the Earth is estimated to have been in the range of 10–15 megatons of TNT—about 1,000 times greater than that of the atomic bomb dropped on Hiroshima.  It knocked down virtually everything standing in 830 square miles, shook the Earth the equivalent of a 5.0 earthquake on the Richter scale, caused fluctuation in atmospheric pressure measured in London, and caused a stratospheric cloud of ice crystals to orbit the Earth for months affecting the climate of the Northern Hemisphere.

But because the explosion on June 30, 1908 occurred over one of the most remote and under populated regions of the Earth—an almost unexplored (by Europeans) forest near the Podkamennaya Tunguska River deep in south-central Siberia—it was barely noted at the time.  Subsequent events—World War I, the Russian Revolution, and the Civil War that followed meant that the site of the Tunguska Event was not investigated until an expedition was finally mounted in 1927, 19 years after the explosion.

On July 2, 1908 first sketchy reports were printed in a Siberian newspaper:

On the 17th of June [Julian calendar still in use in Russia], around 9 a.m. in the morning, we observed an unusual natural occurrence. In the north Karelinski village [200 verst north of Kirensk] the peasants saw to the northwest, rather high above the horizon, some strangely bright (impossible to look at) bluish-white heavenly body, which for 10 minutes moved downwards. The body appeared as a “pipe”, i.e., a cylinder. The sky was cloudless, only a small dark cloud was observed in the general direction of the bright body. It was hot and dry. As the body neared the ground (forest), the bright body seemed to smudge, and then turned into a giant billow of black smoke, and a loud knocking (not thunder) was heard, as if large stones were falling, or artillery was fired. All buildings shook. At the same time the cloud began emitting flames of uncertain shapes. All villagers were stricken with panic and took to the streets, women cried, thinking it was the end of the world.

The author of these lines was meantime in the forest about 6 verst [6.4 km] north of Kirensk and heard to the northeast some kind of artillery barrage, which repeated in intervals of 15 minutes at least 10 times. In Kirensk in a few buildings in the walls facing northeast window glass shook.

Scattered reports reached Moscow within days but received surprisingly scant interest.  No official or scientific investigations were undertaken to find out what the hell happened out there in the boonies.

                               

                                             Soviet Mineralogist Leonid Kulik led expeditions to investigate what had happened twenty years after the fact.

Finally in 1921, as the Civil War was winding down, mineralogist Leonid Kulik was dispatched by the Soviet Academy of Sciences to the Podkamennaya Tunguska River basin not to investigate the incident 13 years early but as part of a survey to discover possible natural resources in the remote area.  He began hearing stories of the mysterious event from locals and started informally collecting evidence as well as he could without actually traveling to the area of the impact.  He concluded a large meteor or small asteroid had either struck the Earth or exploded on entry relatively close to the surface.

Kulik spent years trying to convince Soviet science authorities to fund a full-scale expedition to the site.  But the practical commissars keeping a close eye on those foolish scientists had little interest in abstract science or basic research.  They insisted that some tangible and practical economic benefit must be the result of any investigation. 

Finally, Kulik convinced them that he might be able to locate a very large nickel/cadmium/iron meteorite, the kind representing some of the densest and hardest stone found on Earth, which could be useful in the Soviet steel industry.  He had to do this with fingers crossed behind his back knowing that even if such a meteorite had struck the earth, it would have shattered into small fragments spread over a wide area and unlikely to be recoverable in any economically viable amounts.

None-the-less Kulik arrived in the area in 1927 at the head of a well-supplied expedition.  He contracted with local Evenks, indigenous semi-nomadic reindeer herders and hunters, to guide him from remote Russian trading outposts to the site.  Travel through dense forests cut by numerous rivers and streams was extremely difficult.  But after weeks of travel the group neared the target area.  Then, just south of the site, the Kulik guides flatly refused to take him further, fearing possible supernatural beings called valleymen associated with the site.  Kulik had to turn back to a village and arrange for new guides.

Finally, the expedition reached a ridge overlooking the impact area.  To Kulik’s surprise, he could detect no discernible impact crater.  Instead around ground zero he found a vast zone more than 5 miles across of trees scorched and devoid of branches but standing upright.  Trees further from the center were more lightly singed.  Closer in but all knocked over in a direction away from the center was a giant ring of flattened trees radiating outward from an invisible center.  

In 1927 Kulik found a ring of trees knocked down outward from a suspected epicenter.

Kulik led three more expeditions to the area looking for evidence of an impact.  His best hope seemed to be numerous small pothole bogs which he thought might have been created by meteorite fragments.  But this turned out to be a blind alley.  Draining one turned up an old tree stump at its bottom, not extraterrestrial stone.

The Soviets continued to send teams of investigators to the region for decades but the mystery of just what had happened only deepened.  Eventually microscopic beads of silicate and magnetite were found in the soil, and still later similar beads were found in the resin of some trees.  The beads or spheres also contained significant traces of nickel iron similar in composition to that found in meteorites.  All of this bolstered the opinion that an object from space was involved, but that it had likely been virtually destroyed by an explosion in the atmosphere.  That became the most widely accepted theoretic explanation of the event.

Atmospheric nuclear tests it the ‘50s and ‘60s seemed to confirm the hypothesis that an asteroid exploded.  Air bursts over forests showed that trees directly under the blast were stripped as the blast wave moved vertically downward, while trees farther away were knocked over because the blast wave was traveling closer to horizontal when it reaches them.  

Map based on Kulik's observations showing the suspected epicenter, trajectory of the meteor or asteroid fragment, and the rings of devastation.  The inset shows the location in the Soviet Union with K representing the impact zone. 

By then aerial surveys showed the blast area was actually in the “shape of a butterfly with wings outstretched” occupying an area of 830 square miles, with a wingspan of 43 miles and a body length of 34 miles.  Soviet experiments performed in the mid-‘60s, with model forests and small explosive charges slid downward on wires, produced strikingly similar butterfly-shaped blast patterns suggested that an extraterrestrial object had approached at an angle of roughly 30 degrees from the ground and 115 degrees from north and exploded in mid-air. 

Making up for the lack of interest in the first few years, the Tunguska Event continues to arouse and challenge science to come up with new techniques and technologies almost yearly to discovering what happened.  The exploding asteroid theory remains the top contender, but the continuing absence of any fragment of the object has opened the door to other conjectures. 

Among the several theories advanced, the one which picked up the most steam was that instead of an asteroid, the object was a small comet or a fragment of a larger comet that had disintegrated in orbit earlier.   Advanced by some Soviet scientists in the 1930’s, the fact that the head of a comet—made up of ice particles and space dust exploding in the atmosphere would explain why no physical debris has been found on earth.  Dissipation of the ice crystals into the upper atmosphere could also explain the “glow” that was reported for some days after the event and the orbiting particles that reduced sunlight hitting the Earth over the next year.

In the ‘70s the Soviets even advanced a candidate, fragment of the short-period Comet Encke, which is responsible for the Beta Taurid meteor shower which coincided with the event.  Later Western research has cast doubt on the comet theory pointing out that a comet reaching the atmosphere at the low angle expected would have exploded or vaporized far earlier and not nearly reached the surface, if a handful of miles can be said to be near the surface.  Other research showed that the object came in a direction from the Asteroid Belt.

Lake Cheko thought by some to have been formed from the impact crater.

If the comet idea was doubtful, scientists were still troubled by the absence of physical evidence that a hard stony object like an asteroid should have left behind.  Then in 2007 a candidate for the long-sought impact crater was brought forwards—Lake Cheko, a small, bowl-shaped lake a little more than 4 miles north-northwest of the epicenter.  Magnetic readings indicated a possible meter-sized chunk of rock below the lake’s deepest point that may be a fragment of the colliding body and chemical analysis of the lake silt supported a creation about the time of the impact.  Scientists from the University of Bologna led by Professor Giuseppe Longo have pressed the case that the long-missing impact crater and a fragment may have been found.  Other experts are skeptical.

In 2005 a near earth object identified as 2005 NB₅₆ was observed for a 17-day period as it neared the Earth.  Its exact orbit could not be calculated, but some scientists believe that a large fragment of it in may have brushed the atmosphere in 1908 causing the explosion and then skipping or bouncing back into orbit around the Sun.  They believe that the object will again near the earth in 2048 and hope that better calculation of its orbit would be able to confirm it as a candidate.

A couple of proposals have been put forward involving a “natural H-bomb.”  In these scenarios unusually large concentrations of deuterium—heavy hydrogen—in the head of a small comet underwent a nuclear fusion reaction when it entered the atmosphere.  Two or three explanations of how this could have been triggered have been advanced.  Most scientists believe that that the concentration of radioactive isotopes in the blast region to be inconsistent with those expected following a nuclear explosion.

Probably the oddest of all theories seriously advanced was that the earth was actually struck by a small black hole which passed through the planet exiting on the other side.  This one has most scientists shaking their heads in disbelief.  If this were the case, there should have been and exit explosion of similar magnitude.  Even though at the expected trajectory, the exit would have occurred somewhere in the North Atlantic, closer than the impact event to the seismic recording stations that collected much of the evidence of the event and would likely have been observed by ships in the region.

A similar proposal suggested a collision with an anti-mater object.  Neither of those explanations takes into account the orbiting dust trails in the atmosphere or the distribution of high-nickel magnetic micro-beads around the impact area.

One scientist has even suggested that there was no collision or impact of any sort, but rather huge eruption and explosion of 10 million tons of natural gas from within Earth’s crust.  Few are taking a bite out of that apple, especially since just as an impact crater has been hard to find, there is no geologic evidence of an outward explosion from the crust.  But with global warming threatening to release vast quantities of frozen methane or natural gas below the Siberian frost line that scenario raises frightening possibilities.

After more than 120 years tree growth is returning to the devastated area, although many of the logs of the downed trees observed in 1927 lay between new growth.  But at the center,   trees have not returned, although they theoretically should have.  More fodder for scientists and pseudo-scientists alike.

But then so does being struck by an asteroid as scientists believe that a collision with one or more is inevitable and only a matter of time.  Asteroid collisions are the most likely causes for several mass extinctions on Earth—including the one that doomed the dinosaurs. 

Despite all of the other conjectures most scientists keep coming back to that wayward asteroid.

But I am sure as I type that the History Chanel is preparing a “documentary” on the Tunguska Event blaming aliens.  Or maybe they already have….

The Great Chicago Fire and Other Burns Charred the Great Lakes Region

 

The Chicago and Peshtigo, Wisconsin fires of October 8, 1871 were just two of the deadly blazes that swept the upper Midwest that day.  Libraries in Illinois and Wisconsin hosted a virtual on-line discussion on the 150th anniversary during the Covid year of 2021.

You may have noticed that this is National Fire Protection Week.  The annual event is marked by news stories extolling the virtues of smoke alarms and family fire evacuation drills.  Your local fire station may host school field trips or an open house—maybe they will let you climb on an engine or even slide down a pole.  Ask and you will be told that this week was selected because the Great Chicago Fire broke out on October 8, 1871.

This is the anniversary of that conflagration—and also of little remembered but even deadlier Midwestern fires.

The Chicago fire was certainly memorable.  After breaking out in an immigrant South Side neighborhood, winds whipped flames north and west across the sprawling city.  It burned for two days consuming 4 square miles, including the downtown business district, killing an estimated 200-300 and leaving 90,000 people homeless.  The fire originated in the O’Leary family barn—the house was spared because it was up wind—but neither the lady of the house or her cow had anything to do with it.  Apparently neighborhood layabouts set it off while shooting craps.  

A popular contemporary lithograph print showed an imaginary aerial view of the Great Chicago Fire after it jumped the Chicago River burning the North side of the the city.

Word of the fire spread rapidly across the country and within a week national publications were carrying firsthand accounts and illustrations of the carnage.  The city famously rose from the ashes, replacing its largely ramshackle wooden buildings with modern—and fire resistant—brick and stone.  In less than a decade the city had not only fully recovered, but it had also doubled again in size.

But the fire in Chicago was not the only conflagration that day.  After an extended long drought that covered the entire upper Midwest, a fast moving cold front drove intense winds before it.  Fires swept Holland and Manistee, Michigan and swaths of surrounding areas on the east shore of Lake Michigan.  More than 200 died when another fire consumed Port Huron, Michigan on the southern shores of Lake Huron.

As devastating as those fires were, they all paled compared to the great fire in Wisconsin’s North Woods centered on the lumber town of Peshtigo.  Despite tinder dry conditions, careless neglect sparked several fires in the area that had burned more or less unchecked for several days.  These fires were attributed to cinders from railroad locomotive smokestacks, small heating and cooking fires left unattended by hunters, farmers burning to clear brush of the treetops stripped from logging operations.  Local experience was that these fires would burn themselves out or be extinguished by the early snows expected in the region by mid-October.  The night before the big fire survivors reported seeing several small blazes on surrounding hills.

A family seeks refuge from the Peshtigo fire in cleared farm field.

By the evening of the October 8 high winds were merging the fires, which began to move on broad fronts burning, among other things, the telegraph lines that Peshtigo and another dozen small towns could have used to signal for help.  By the time a wall of flame erupted over a ridge near town, the fire was roaring with unprecedented fury, moving at high speed directly on the town.  Residents had little time to gather possessions and attempt to flee before the town itself was engulfed.  By then the fire was traveling from treetop to treetop creating its own cyclonic winds, including at least one “tornado of fire” witnessed by several survivors.  The firestorm fed itself creating internal winds of up to 80 miles an hour ripping the roofs off houses, blowing over barns, uprooting trees, and tossing a 1,000 lb. wagon like tumbleweed.

Before it was over the fire burned over 1.2 million acres.  Winds carried embers to both sides of the Peshtigo River and across Green Bay where it burned the Door Peninsula from Dykesville almost to Sturgeon Bay to the north.  Sixteen towns were totally destroyed.  In Peshtigo alone, 800 lives were lost.  The total death toll will never be known exactly because town records across the region were destroyed and whole families wiped out.   In addition, hundreds of lumber workers, isolated small farmers, hunters, and trappers were in the woods with no way to determine their fate.  Best estimates of the death toll range from 1,200 to over 2,000.  

High winds carried burning embers from the Peshtigo file all the way across Green Bay.

Word of the Peshtigo fire and the other disasters in the north was overwhelmed by news from Chicago.  To this day the largest loss of life by fire in American history remains little known outside of Wisconsin and among fire historians. 

During World War II, however, the Army Air Force was aware of the historic firestorm.  It commissioned American and British scientists to study it to find ways of duplicating the firestorm through incendiary bombing.  The destruction of Dresden, Germany by fire storm, which took more lives than either of the atomic bombs used against Japan, was partly the result of that research.

 

Firenados like this were seen with the firestorms around Peshtigo and other Upper Midwest communities.  These reports were long thought to be exaggerations until firenados  were observed in Western wildfires and in Australia.

Today a museum in Peshtigo commemorates the fire.  It has very few relics of the town—almost everything burned up except for one house freshly built of green lumber.  Among the few artifacts of the fire are the Tabernacle from the Catholic Church which was saved by survivor Father Peter Pernin by submersing it in the river, a melted can of peas, some fused ceramics, a charred piece of lumber from the surviving house, and artifacts recently dug up, including a Bible discovered opened to Psalms.

Despite the fact that conditions across the region were perfect for widespread fire, that many eyewitness accounts of numerous fires burning for days around the town, and that the origin of the Chicago fire can be traced to the O’Leary barn, speculation that the fires had some common origin has gone on for years.  As early as 1883 there was speculation that the fires across the region might have been caused by impact of debris from the Comet Biela, which was observed to break up in its 1854 appearance.  The intersection of the projected route of the comet’s return in November 1872 was marked by an intense meteor shower. 

The 1985 book Mrs. O’Leary’s Comet: Cosmic Causes of the Great Chicago Fire by Mel Waskin revived that theory.  In 2007 Robert M. Wood published a scholarly article in the Journal of the American Institute of Aeronautics and Astronautics which calculated that gravitational pull of Jupiter when debris of the comet crossed its path may have accelerated the arrival of that debris by as much as a year.  Observations of “fire balls” falling from the sky in both the Peshtigo and Chicago fires might have been burning gasses from the dead comet. 

Other experts remain skeptical of this theory. Many dismiss it as the kind of pseudo-science peddled on the History Channel.  The skeptics point out that the extreme and prolonged drought and gale force winds over a wide area is a sufficient explanation. Their argument has been fortified by the scores of independently started but near simultaneous fires that swept the Western United States and Canada in 2017 in very similar conditions and this year’s deadly Maui Fire in Hawaii.

One thing we know for sure.  Mrs. O’Leary’s innocent cow had a better press agent than the victims of the Peshtigo inferno. 

The Tunguska Event Was Not a Sale at an Import Car Dealership

Russian scientist Leonid Kulik photographed these trees knocked over like matchsticks near the epicenter of a mysterious Siberian blast in 1927.

It was the largest impact event on or near Earth in recorded history.  An explosion three to six miles above the surface of the earth is estimated  to have been in the range of 10–15 megatons of TNT—about 1,000 times greater than that of the atomic bomb dropped on Hiroshima.  It knocked down virtually everything standing in 830 square miles, shook the earth the equivalent of a 5.0 earthquake on the Richter scale, caused fluctuation in atmospheric pressure measured in London, and caused a stratospheric cloud of ice crystals to orbit the earth for months affecting the climate of the Northern Hemisphere.

But because the explosion on June 30, 1908 occurred over one of the most remote and underpopulated regions of the earth—an almost unexplored (by Europeans) forest by the near the Podkamennaya Tunguska River deep in south-central Siberia it was barely noted at the time.  Subsequent events—World War I, the Russian Revolution, and the Civil War that followed meant that the site of the Tunguska Event was not investigated until an expedition was finally mounted in 1927, 19 years after the explosion.

On July 2 first reports were printed in a Siberian newspaper.

On the 17th of June (old calendar still in use in Russia), around 9 a.m. in the morning, we observed an unusual natural occurrence. In the north Karelinski village [200 verst north of Kirensk] the peasants saw to the north west, rather high above the horizon, some strangely bright (impossible to look at) bluish-white heavenly body, which for 10 minutes moved downwards. The body appeared as a “pipe”, i.e., a cylinder. The sky was cloudless, only a small dark cloud was observed in the general direction of the bright body. It was hot and dry. As the body neared the ground (forest), the bright body seemed to smudge, and then turned into a giant billow of black smoke, and a loud knocking (not thunder) was heard, as if large stones were falling, or artillery was fired. All buildings shook. At the same time the cloud began emitting flames of uncertain shapes. All villagers were stricken with panic and took to the streets, women cried, thinking it was the end of the world.

The author of these lines was meantime in the forest about 6 verst [6.4 km] north of Kirensk, and heard to the north east some kind of artillery barrage, that repeated in intervals of 15 minutes at least 10 times. In Kirensk in a few buildings in the walls facing north east window glass shook.

Scattered report reached Moscow within days, but received surprisingly scant interest.  No official or scientific investigations were undertaken to find out what the hell happened out there in the boonies.

Finally in 1921, as the Civil War was winding down, mineralogist Leonid Kulik was dispatched by the Soviet Academy of Sciences to the Podkamennaya Tunguska River basin not to investigate the incident 13 years early but as part of a survey to discover possible natural resources in the remote area.  He began hearing stories of the mysterious event from locals, and started informally collecting evidence as well as he could without actually traveling to the area of the impact.  He concluded a large meteor or small asteroid had either struck the earth or exploded on entry relatively close to the surface.

Kulik spent years trying to convince Soviet science authorities to fund a full scale expedition to the site.  But the practical commissars keeping a close eye on those foolish scientists had little interest in abstract science or basic research.  They insisted that some tangible and practical economic benefit must be the result of any investigation.  Finally he convinced them that he might be able to locate a very large nickel/cadmium/iron meteorite, the kind representing some of the densest and hardest stone found on earth, which could be useful in the Soviet steel industry.  He had to do this with both fingers crossed behind his back knowing that even if such a meteorite had struck the earth, it would have shattered into small fragments spread over a wide area and unlikely to be recoverable in any economically viable amounts.

None-the-less Kulik arrived in the area in 1927 at the head of a well-supplied expedition.  He contacted with local Evenks,  indigenous semi-nomadic reindeer herders and hunter to guide him form remote Russian trading outposts to the site.  Travel through dense forests cut by numerous rivers and streams was extremely difficult.  But after weeks of travel the group neared the target area.  Then, just south of the site,  the Kulik guides flatly refused to take him further, fearing possible supernatural beings called valleymen associated with the site.  Kulik had to turn back to a village and arrange for new guides.

Finally the expedition reached a ridge overlooking the impact area.  To Kulik’s surprise, he could detect no discernible impact crater.  Instead around ground zero a vast zone more than  5 miles across of trees scorched and devoid of branches, but standing upright.  Trees further from the center were more lightly singed, but all knocked over in a direction away from the center—a giant ring of flattened trees radiating from an invisible center. 

Kulik led three more expeditions to the area looking for evidence of an impact.  His best hope seemed to be numerous small pothole bogs which he thought might have been created by meteorite fragments.  But this turned out to be a blind alley.  Draining one turned up an old tree stump at its bottom, not extraterrestrial stone.

The Soviets continued to send teams of investigators to the region for decades but the mystery of just what had happened only deepened.  Eventually microscopic beads of  silicate and magnetite were found in the soil, and still later similar beads were found in the resin of some trees.  The beads or spheres, also contained significant traces of nickel iron similar in composition to that found in meteorites.  All of this bolstered the opinion that an object from space was involved, but that it had likely been virtually destroyed by an explosion in the atmosphere.  That became the most widely accepted theoretic explanation of the event.

Atmospheric nuclear tests it the ‘50’s and ‘60’s seemed to confirm the hypothesis that an asteroid exploded.  Air bursts over forests showed that trees directly under the blast were stripped as the blast wave moved vertically downward, while trees farther away were knocked over because the blast wave was traveling closer to horizontal when it reaches them. 

By then aerial surveys showed the blast area was actually in the “shape of a butterfly with wings outstretched” occupying an area of 830 square miles, with a wingspan of 43 miles and a body length of 34 miles.  Soviet experiments performed in the mid-‘60s, with model forests and small explosive charges slid downward on wires, produced strikingly similar butterfly-shaped blast patterns  suggested that an extraterrestrial  object had approached at an angle of roughly 30 degrees from the ground and 115 degrees from north and had exploded in mid-air. 

Making up for the lack of interest in the first few years, the Tunguska Event continues to interest and challenge science with new techniques and technologies applied almost yearly to discovering just what happened.  The exploding asteroid theory remains the top contender, but the continuing absence of any fragment of the object has opened the door to other conjectures. 

Among the several theories advanced, the one which picked up the most steam was that instead of an asteroid, the object was a small comet or a fragment of a larger comet that had disintegrated in orbit earlier.   Advanced by some Soviet scientists in the 1930’s, the fact that the head of a  comet—made up of ice particles and space dust exploding in the atmosphere would explain why no physical debris has been found on earth.  Dissipation of the ice crystals into the upper atmosphere could also explain the “glow” that was reported for some days after the event and the orbiting particles that reduced sunlight hitting the earth over the next year.

In the ‘70’s there Soviets even advanced a candidate, fragment of the short-period Comet Encke, which is responsible for the Beta Taurid meteor shower which coincided with the event.  Later Western research has cast doubt on the comet theory pointing out that a comet reaching the atmosphere at the low angle expected would have exploded or vaporized far earlier and not nearly reached the surface, if a handful of miles can be said to be near the surface.  Other research showed that the object came in a direction from the asteroid belt.

If the comet idea was doubtful, scientist were still troubled by the absence of physical evidence that a hard stony object like an asteroid should have left behind.  Then in 2007 a candidate for the long sought impact crater was brought forwards—Lake Cheko, a small, bowl-shaped lake approximately a little more than 4 miles north-northwest of the epicenter.  Magnetic readings indicated a possible meter-sized chunk of rock below the lake’s deepest point that may be a fragment of the colliding body and chemical analysis of the lake silt has supported a creation about the time of the impact.  Scientists from scientists from the University of Bologna led by professor Giuseppe Longo have pressed the case that the long missing impact crater and a fragment may have been found.  Other experts are skeptical.

In 2005 a near earth object identified as 2005 NB₅₆ was observed for a 17 day period as it neared the earth.  Its exact orbit could not be calculated, but some scientists believe that a large fragment of it in may have brushed the atmosphere in 1908 causing the explosion and then skipping or bouncing back into orbit around the sun.  They believe that the object will again near the earth in 2048 and hope that better calculation of its orbit would be able to confirm it as a candidate.

A couple of proposals have been put forward involving a “natural H-bomb.”  In these scenarios unusually large concentrations of deuterium—heavy hydrogen—in the head of a small comet underwent a nuclear fusion reaction when it entered the atmosphere.  Two or three explanations of how this could have been triggered have been advanced.  Most scientists believe that that the concentration of radioactive isotopes in the blast region to be inconsistent with those expected following a nuclear explosion.

Probably the oddest of all theories seriously advanced was that the earth was actually struck by a small black hole which passed through the planet exiting on the other side.  This one has most scientists shaking their heads in disbelief.  If this were the case there should have been and exit explosion of similar magnitude.  Even though at the expected trajectory, the exit would have occurred somewhere North Atlantic, closer than the impact event to the seismic recording stations that collected much of the evidence of the event and would likely have been observed by ships in the region.

A similar proposal suggested a collision with an anti-mater object.  Neither of those explanations takes into account the orbiting dust trails in the atmosphere or the distribution of high-nickel magnetic micro-beads around the impact area.

One scientist has even suggested that there was no collision or impact of any sort, but rather huge eruption and explosion of 10 million tons of natural gas from within Earth’s crust.  Few are taking a bite out of that apple, especially since just as an impact crater has been hard to find, there is no geologic evidence of an outward explosion from the crust.

Despite all of the conjecture most scientists keep coming back to that wayward asteroid.

But I am sure as I type that the History Chanel is preparing a “documentary” on the Tunguska Event on aliens.  Or maybe they already have….