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The problem of the nature of the 1908 Tunguska event has already excited
researchers over the course of many decades and there is no consensus on
Tunguska still (see results of "what was Tunguska" internet poll
here).
A 100-th Anniversary celebrations just confirmed that 'Tunguska is still a mystery' (see:
http://www.cnn.com/2008/TECH/science/07/04/tunguska.anniversary/index.html ).
In the morning of June 30, 1908, the ground trembled north and northwest of Lake Baikal in Central Siberia, and underground jolts struck panic into the hearts of the local population. Reports of a glowing body flying over came from various points of the territory. The Tunguska forest fall, called the "impact/explosion site" or the "epicenter" was discovered just in 1927 at 61 N & 102 E, i.e. in the northern part of the Tunguska event manifestations region. Various conjectures were soon offered in 1908 to explain the nature of the Tunguska event. The most popular were a meteorite fall, a ball lightning (or its formation) and an earthquake (because of the seismic phenomena). Since official science of the time put in doubt the existence of ball lightning, while the possibility of glow occurring during earthquakes was, as a rule, rejected, and a false report about a meteorite fall near a town of Kansk appeared, the general consensus was that a very large meteorite had come down in Siberia. Attempts to put forward any other interpretations of the Tunguska event had been quashed for many years.
Since that time the situation with the "meteorite fall" Tunguska rather
resembles a pendulum: one group of scientists turns up new strong evidences
that Tunguska event couldn't have been caused by an asteroid made of stone or
iron, thus it had to be caused a comet.
Pretty soon, another group of scientists comes up with new strong
arguments that Tunguska could not have been a comet, thus it must have been
an asteroid!
The number of supporters of each idea varies with time.
The latest maximum for the "asteroid" Tunguska was around 1995. Since then,
the attractiveness of an asteroid explanation seems to decline again.
These swings hint that both groups are right and wrong at the same
time: Tunguska 1908 was neither an asteroid, nor a comet. But then,
what was it?
Many researchers seeing the failure of asteroid/comet interpretation proposed other ideas: a "black hole", an "antimatter bullet", and, of course, UFO (the latter one is, no doubt, the most correct: indeed the event was related with some "unindentified flying object", or sooner with "objects", as it is shown in the link below!).
In late 1980-s I came up with the idea that Tunguska event was something
completely different, not a cosmic, but a geophysical event, associated with
tectonic processes. My idea, which in
the meantime has been presented at several scientific conferences as well
as in scientific journals, should not be confused with an earthquake,
although earthquakes were indeed associated with the 1908 explosion.
It was a more complicated event of tectonic origin in which atmospheric
processes played a large role. So probably we can call Tunguska
as tectono-atmospheric phenomenon. Now we can just to admit that it
was related with some still poorly understood processes of the Earth
electricity, but it is just a speculation.
Unfortunately, till now, such phenomena are little known and poorly
understood. Moreover, there is no scientific term accepted for the
phenomena still. I prefer to call as a "geophysical meteor" or just a "geometeor"
(you can read about it here). In a very simplified
form often it can be imagined as an explosion of an energetic high-speed
ball-lightning.
So this my idea idea (first it was published in IZVESTIA ACADEMY
OF SCIENCES OF USSR in 1991, and now it is already rather popular among
Tunguska researchers) explains that the 1908 Tunguska event was a
manifestation of geophysical (terrestrial) processes, and the most probably,
a result a some kind of coupling between tectonic and meteorological
processes in very rare combination of favourable geophysical factors.
In general the idea is based on the following:
Below is a text of my report (see related pictures in
http://olkhov.narod.ru/tunguska.htm)
at the conference
"Environmental Catastrophes and Recovery in
the Holocene" (Brunel Univ., Uxbridge, UK, Aug.28-Sept.2, 2002).
Also below you can read a SCIENCE magazine's note on it.
Nowadays the situation with so called "Tunguska meteorite"
resembles a pendulum: one group of scientists turns up new
(and old too) strong evidence that Tunguska couldn't have been an
asteroid made of stone or iron, thus it had to be a comet. But
pretty soon, another group of scientists comes up with new (and
old too) strong arguments that Tunguska could not have been a comet,
thus the only way-out is that it must have been an asteroid.
These swings hint that both groups are right and wrong at the same
time: Tunguska 1908 was neither an asteroid, nor a comet.
And indeed, now I try to demonstrate that it could not have been any
known spacebody-fall.
A main reason to attribute the Tunguska to the fall of a meteorite
were reports about flying fiery body. Let's look at these 'flying
bodies' carefully from our modern knowledge.
- Analysis of the most reliable witness's accounts conducted in 1920s
and 1930s showed that the Tunguska spacebody flew from the south to
the north. But in 1960s a new group of witness's accounts was collected
pointing to quite another trajectory: almost from east to west!
- Even just in a few days-weeks after the event different time was
given by different witnesses, from early morning to the afternoon.
Conducted in 1980s statistical analysis revealed that the "afternoon"
accounts are not at the edge of statistical dispersion, but form
a distinct secondary maximum. So was the duration of the event: from a
few minutes to an hour.
- Many witness's accounts hardly conformed to the meteorite fall,
as a shape and luminosity of flying object reported in many cases
does not resemble a bolide, including such strange as darkening of the
sky. And there was no any smoke trail at all!
- Remarkably that, in the area within 200 km around the epicenter,
witnesses did not see any bolide or just even its trail, at least, but
they saw flames shooting up, and fire pillars, flashes in the sky and
other non-bolide luminosities.
Here is a map of the famous "butterfly" pattern of the Tunguska forest-fall.
--------------------------------
PICTURE (omitted here)
--------------------------------
Now I will try to show that the forest-fall could not be produced
by a stony meteorite or by a cometary "explosion". Here are just a few
of the arguments:
- The Tunguska explosion detailed numerical simulation undertaken
by Victor Korobeinikov with his co-workers has shown that there must be
some additional (internal) source of the "explosion's" energy, and
moreover, the source's energy is to be commensurate with spacebody
kinetic energy to produce the forest-fall. In plain language, this means
that the Tunguska meteorite had to be an enormous block of super-explosive!
- These calculations also shows that the angle of inclination of the
hypothetical spacebody trajectory must be about 40 degrees, while from
witness's accounts it must be no more than about 10-15 degrees. The
only way-out for the meteorite interpretation is to propose that the angle
was changed during its flight because of "non-zero aerodynamic lift",
but due to evident reasons avoiding to discuss details of such "guided
flight".
Moreover there are peculiarities of the Tunguska forest fall, which
can not be produced by any known type of a spacebody fall:
- An effect of rotation of fallen trees in the epicentral area. The
rotation achieved 5 degrees clockwise in the epicenter, decreasing to
negligibly small values at about 16 km from the epicenter. So the field
of the mean directions of the tree-fall is the vortex one. In other
words, the hypothetical Tunguska spacebody explosion's shock wave was
to transfer a very large angular momentum. But such explosion couldn't
produce it due to a law of conservation of angular momentum. [Addition of the year 2007: my new detailed research and research of some other Tunguska researchers shows that the rotation (revealed in mid-1960s) could be a computational artefact sooner.]
- One more puzzle for the spacebody interpretation is the area of the
forest fall on the ridge Chuvar, which is about 23 km from the epicenter,
and according to the local Evenks had formed the same morning as the
general one. The peculiarity of this forest fall is that trees were
uprooted with their tops in the opposite of what was expected from the
meteorite fall direction.
The tree burn in the epicenter is a remarkable and important aspect of
the Tunguska event. Indeed some cases of the ignition of wood bedding
were reported up to 34 km from the epicenter. So the burn must be many
times stronger right in the epicenter, and everything alive would
completely burn into ashes at the epicenter.
In reality many groups of trees survived at the epicenter. Moreover,
some single standing trees in open places of the epicenter had no
visible traces of the burn!
No "Tunguska meteorite" fragments were discovered, despite many years of careful search over vast area. Some minor geochemical anomalies were detected in the epicentral area, but their origin is uncertain. It is important to mention that the isotopic ratio for rare Earth elements in the Tunguska epicenter, which was measured in the place of their most enrichment is a terrestrial ratio. Till now meteorite interpretation has no plausible explanation of the absence of any traces of the spacebody substance.
The Tunguska event is also associated with other disturbances and anomalies,
as, for example, unusual pattern of seismic manifestations, which also don't
conform with the meteorite fall, but unfortunately, I have no time to discuss
them.
But, as we see, the already considered anomalies don't conform with
a stony asteroid or a comet fall.
In late 1980s I proposed a large role of tectonic and some other geophysical processes in Tunguska event, and began to investigate various geophysical circumstances of Tunguska event, especially its tectonic and meteorological. The investigation brought very interesting data. Here I show that the event took place during a remarkable and rare combination of geophysical factors on regional, and partly, global levels.
From the geological
aspect, the Tunguska event occurred in a rather
remarkable place in the
southern part of the Siberian platform.
It was the place of one
of the most powerful volcanic activity
in Earth's history 250
millions years ago, a former "hotspot".
The area is rich in
various gas/oil and ore deposits, including
rare earth elements, and
platinoids. There are kimberlites in the
region too.
The
upper mantle in this region has anomalous
speeds of seismic waves.
The Tunguska epicenter
is right in the middle of the paleovolcano
crater. Here the
paleovolcano is seen on a satellite picture taken
in
the near-infrared.
-----------------------------------
PICTURE (omitted here)
-----------------------------------
Also the Tunguska event occurred in the intersection area of several prominent tectonic faults in the region
---------------------------------------
PICTURE (omitted here)
---------------------------------------
It is remarkable, that
all main hypothetical Tunguska spacebody
trajectories coincide with
the most powerful tectonic faults in the
region, as well as, the
Tunguska event reported luminosities resemble
"earthquake lights" very much.
To check seismic
activity in the Tunguska event region, I
have investigated a catalog
of Baikal-region earthquakes for 1908 and
also for near-by years.
The result is the
following. In 1906 just 1 earthquake to the north
of Baikal was registered,
in 1907 the number was 2, in 1908 - 6
(including the one
associated with Tunguska event), in 1909 - no
earthquakes,
in 1910 - 1.
In other words, in 1908
an upsurge of tectonic activity took place
in the region of the
Tunguska event.
Distribution of
earthquakes in the Baikal rift region and
surroundings inside year
1908 is also remarkable and is shown here.
---------------------------
PICTURE (omitted here)
---------------------------
So, there was a
peak of regional tectonic activity at
about the Tunguska date.
Interestingly, that at
about that time an unusual phenomenon was
discovered near Ust'-Kut
settlement: a hot "salted" spring with
various chemical elements,
which was absent in previous summer.
There are also evidences
of activation of tectonic processes at
the time on larger scales
too. The evidences are as follows.
I searched through a
catalog of the position of the Earth axis of
rotation, together with the
"momentary" polhode radius of the
Earth axis trajectory on
the Earth surface (in plain language, the
trajectory of the North
Pole).
--------------------
PICTURE (omitted here)
--------------------
You can see that between
June 14 and July 2 the strongest
decrease of the polhode
radius has occurred. The rate (per time) of
relative change of the
polhode's radius for this period was the
largest not only in 1908
but also for the whole period of 1907-1910!
In general, there was a
decrease of a total number of earthquake
reports in summer 1908, so
the seismic energy release that year was
one of the lowest for the
20th century. But on another side, on June 30
and July 1 the number of
registered earthquakes was increased. It is
shown on the picture
----------------------------------------
PICTURE (omitted here)
----------------------------------------
So there are strong evidences of significant activation of tectonic processes in the Tunguska event region, and possibly even of large-scale disturbances in the Earth interior at about the Tunguska date.
It is important, that
besides tectonic, there were also other
numerous geophysical
peculiarities in that period of time on
regional, as well as, on
much larger scale.
For example, there were
some peculiarities in global
atmospheric circulation at
about the Tunguska date. Cyclones over
Siberia in June were much
deeper than usual, it led to significant
increase of air pressure
gradients.
Another peculiarity was
very warm weather in this part Siberia (and
even partly in Europe) in
the second half of June. Together with
the small number of
thunderstorms it led to drought in some
regions.
At the beginning of July
the situation sharply changed. There
was a strong increase in
thunderstorm activity. For example in the
Perm' province, Russia in
July a quantity of precipitation was a
record high for the whole
70 previous years of measurements.
In the Tunguska event
region level of rivers raised leading to
floods in some areas.
Powerful thunderstorms took place.
On larger-scale level
the Arctic area of high pressure
sharply decreased in
dimensions.
I have discovered that in
the Tunguska event region a change from
good weather to a bad
weather was right on June 30, 1908.
Here is averaged daily
cloudiness data of 9 meteorological stations
situated within 1000 km
from the Tunguska epicenter (the
closest was 500 km away).
----------------------------------------
PICTURE (omitted here)
----------------------------------------
And even more remarkable aspect. Tunguska event occurred exactly at the time of a maximum of atmospheric pressure strong upsurge in the region. In the best way it is seen from the data of the Irkutsk station, which had a log of data with sampling rate every 3 hours.
----------------------------------------
PICTURE (omitted here)
----------------------------------------
Unfortunately, a little is
known on the meteorological data
at the Tunguska epicenter
surroundings.
In most places witnesses
(Evenks) usually described a clear weather
at the time of the Tunguska
event, but in some others, they said
that weather was not so
good, including a sudden rain.
The closest to the
Tunguska epicenter Kezhma meteorological
station was 214 km away.
Its data at about Tunguska time shows a
moderate cloudiness, while
6 hours later it shows the maximum
cloudiness.
In general, statistical
analysis of witness accounts conducted in
early 1980s has revealed
that the Tunguska event was accompanied by
various meteorological
phenomena, including strong winds
(windstorms), haze, fog,
temperature changes, thunderstorms,
whirlwinds.
Remarkably, that in
late 1920-s, while discussing Tunguska
event in Soviet Academy of
Science, prominent Soviet meteorologist
Prof. Mul'tanovskii B.
attracted attention to a possibility of
cyclonic air mass movement
activation at the area on the date of
Tunguska event.
There are also some other evidences of the peculiar geophysical situation at the time of the Tunguska event. Here I just mention that on June 29 the "Alps Glow" phenomenon was registered in Austria. Remarkably, it was the only registration of this phenomenon for the whole 1908 summer! Also, a Greenland ice layer corresponding to the spring-summer of 1908 contains extremely large quantity of terrestrial dust.
Thus there was a
remarkable geophysical situation,
including peculiar tectonic and atmospheric
activity
in the area of the Tunguska
event and partly on larger scales.
Please, pay attention,
that if any of the geophysical peculiarities
taken separately could be
just an accidental coincidence with the
Tunguska
event, the possibility that
they all together were just an accidental
coincidence is very
unlikely.
An exact physical
mechanism of the Tunguska event is unclear. But
on much smaller scales
similar events occur from time to time.
Unfortunately, I have no
time to discuss them in my report. Just a
picture. A non-meteoroidal
luminous ball fell in Spain in 1994 and
produced such a crater.
------------------------
PICTURE (omitted here)
------------------------
Anyway, as we saw, whatever Tunguska was, it could not have been a stony asteroid or a comet fall. Apparently new fresh ideas are needed to invigorate Tunguska research. And also new open-minded researchers, especially Earth scientists, too! There is no doubt that Nature has much more puzzles for us!
Below is a note from SCIENCE magazine - a reaction on the above-mentioneed discussion of Tunguska at the Brunel Univ. conference (SCIENCE's issue of Sept.13, 2002, p.1803):
On the morning of 30 June, 1908, in the remote Tunguska forest of Siberia,
a vast explosion charred and flattened trees across an area nearly as large
as Rhode Island.
Scientists have been mystified for years over the cause, although
prevailing wisdom has it that an extra-terrestrial chunk of ice or rock
struck Tunguska (Science, 20 August 1999, p. 1205).
At a conference in London last week on environmental
catastrophes, physicists from Russia and Germany rejected the 'ET
hypothesis.' Andrei Ol'khovatov, formerly of the Soviet Radio Instrument
Industry Research Institute, noted that decades of research has failed to
find definitive traces of extraterrestrial material. No impact crater has
been found and, more tellingly, patches of trees were left untouched near
the epicenter of the blast.
Wolfgang Kundt, an astrophysicist from Bonn University, Germany,
then proposed an alternative scenario: a massive gas explosion. A large
natural gas deposit lies below the site, a well-known fact unconnected to
the event until now, he said. Kundt has modeled a Tunguska 'outgassing' and
says it would fit with eyewitness accounts of the event.
"The geophysical hypothesis is a fresh idea," says Jesus Martinez-Frias of
the National Aerospace Institute in Madrid, Spain "It could be the answer."
But Ol'khovatov believes Tunguska was a "poorly understood strong coupling
between subterranean and meteorological phenomena" that science is not yet
ready to understand.
There are a lot of info in internet on Tunguska event. It is easy
to become enmeshed, especially for a novice. So for those who don't
consider themselves as experts in Tunguska, I would like to advise to
read a nice popular book "Tunguska fireball" by Surendra Verma (I think
that it could be useful for Tunguska experts too). You could read my
opinion about the book here.
When you have got some "Tunguska education" and want to know "every technical detail",
I can advise to read about Tunguska those authors, who have some
real expertise (experience) in Tunguska research. In my opinion, real
data (facts) are the most important in such articles, so a reader can work out his own opinion on "what was Tunguska" basing on the facts, if
even authors of the articles have another interpretation. Unfortunately, not
many such articles can be found (in open/free access) in internet, especially
in English.
Below are several such articles I would like to advise.
- The first group of articles is by of TOP 1 researcher of Tunguska -
Nikolai Vasil'ev. He was in Tunguska research since 1959 to his death
in 2001. Informally he led Tunguska research since 1963 to 2001. He was
a brilliant scientist with wide field of view and knowledge.
Here is his:
internet article on Tunguska, and its another version.
Unfortunately, his most open article was published just in Russian
(see here). So I have done
its electronic translation into
English. Vasil'ev concentrated on discussions of real Tunguska facts/data, and not on groundless speculations.
- The second group of articles I wwould like to recommend is a group by
researchers from University of Bologna (Italy). Their published results concentrate on search of "remnants of Tunguska spacebody". ...
Below there are links to articles posted on their www-page:
latest research, and early reseach. The authors seem to favour "asteroidal Tunguska". Remarkably that their steady applying of meteorite's interpretation to Tunguska led them to an idea:
"On the basis of the tree fall data and earlier eyewitness testimonies we consider that the Tunguska Cosmic Body was a multiple bolide formed by at least two bodies of similar mass (see papers pdf, 211 kb, pdf, 18.9 Mb). They likely entered the atmosphere very close to each other following parallel trajectories with azimuths ~135� and an inclination of the total combined shock wave axis between 30� and 50�. The first body, with a greater mass, emitted the maximal energy at a height of about 6-8 km. The second, of minor mass, flew a little higher, on the right side and behind the first body, following the azimuth ~135� in the direction of the lake Cheko.
" (www-th.bo.infn.it/tunguska/99-NewMap.htm).
So there must be at least 2 Tunguska spacebodies!...
- The third group of articles I woould like to advise are from well-known Soviet/Russian astronomer Vitalii Bronshten (by the way, he was a nephew of famous communist leader - Lev Trotsky!). Here they are: "The Nature of the Tunguska Meteorite" ( METEORITICS & PLANETARY SCIENCE, vol. 34, no. 5, pp. 723-728 (1999)). and "On the nature of the Tunguska meteorite" ( ASTRONOMY AND ASTROPHYSICS, v.359, p.777-779 (2000) or as Adobe Acrobat pdf-file here). It is interesting to read how Bronshten disputes with the above-mentioned Bologna group, stating that "Tunguska could not have been an asteroid, so it must be a comet".
- If you are interested in geochemmistry, then read this group of articles by Evgenii Kolesnikov with coauthors. Kolesnikov wrote many articles on "discovering Tunguska spacebody substance"
since late 1970s. Here is a link to an article by Rasmussen, Kaare L.;
Olsen, Hans J. F.; Gwozdz, Raymond; Kolesnikov, Euginev M.:
"Evidence for a very high carbon/iridium-ratio in the Tunguska impactor"
(
METEORITICS & PLANETARY SCIENCE, vol. 34, no. 6, pp. 891-895 (1999)).
But their results on composition of the "Tunguska spacebody" are
so unusual (if not strange), that it produced some argue:
METEORITICS & PLANETARY SCIENCE, v.36, p.999-1006 (2001).
- Prof. Wolfgang Kundt
is in Tunguska research since late 1990s. He is strictly against the "space impact Tunguska", and inclines to think that it was a gas outburst from the
Earth interior. Here is one his first articles
"The 1908 Tunguska catastrophe: An alternative explanation"
(
CURRENT SCIENCE, vol.81, N 4, pp.399-407 (2001)) as Adobe Acrobat pdf-file, or
( the 2003 report.
Now Prof. J.P. Morgan from the Cornell Univ. joined Kundt with similar idea of so called verneshots.
And you can discuss all of the above-mentioned at Tunguska-forum: www.topica.com/lists/tunguska/.
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