The document summarizes a scientific report on the Tunguska event of 1908, in which an extraterrestrial object exploded in the atmosphere over Siberia. Witnesses observed a fireball and heard a loud bang, which felled around 80 million trees over 2,150 square kilometers. Though no crater was found, evidence points to an asteroid or comet exploding 5-10 kilometers above the surface. The event generated energy equivalent to 185 Hiroshima bombs but caused no casualties due to the remote location. Scientists still debate whether it was an asteroid or comet and investigate the risks of future impacts.

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THE TUNGUSKA EVENT: IMPACT OF AN
EXTRATERRESTRIAL OBJECT 1908
By
TASMIA SABAHAT
UMER JAMEEL
UMER SHAHID
Department of Earth and Environmental Sciences
Bahria University, Islamabad
2017

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ABSTRACT
On June 30th, 1908 an extraterrestrial object entered the earth atmosphere and exploded in
air over a remote unpopulated area. It caused massive destruction of trees where it
exploded. People living in nearby areas saw a big explosion and spectacular night skies.
Some are threw off their feet and bumped into walls, windows broke, and seismic activity
was recorded throughout the Europe. At start, no scientist team was sent to investigate the
event but when they did, it arose a lot of question of what actually happened. Many started
to make conspiracy theories about what happened that day, while some collected evidence
and studied it to explain what happened. There is still ongoing scientific debate on what
happened and different scientists follow different approaches to explain the event.

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Table of Contents
 The Tunguska Event……………………………………………… 1
 Recorded impacts and effects…………………………………….. 3
 Mystery of exploding object……………………………………… 5
 Conspiracy Theories……………………………………………… 8
 Risk Related to impact……………………………………………. 9
 Minimizing the impact…………………………………………… 10
o Programs Launched………………………………………. 10
o Techniques to Avoid Impact……………………………… 11
 Why you chose it? ........................................................................... 12
 Suggestions………………………………………………………... 12
 Conclusion………………………………………………………… 14
 References…………………………………………………………. 15

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Graphs and Tables
Photograph of trees destroyed in Tunguska event…………………………………... 2
Visualization of Tunguska explosion event…………………………………………. 3
Table Showing difference in asteroids, comets, meteorites…………………………. 5
Idealized view of meteorite entering earth atmosphere …………………………….. 6

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CONTENTS
Introduction to the hazard
Its recorded impacts and effects
Mystery of exploding object
Conspiracy Theories
Risk Related to impact
Minimizing the impact
Why you chose it?
Suggestions

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Since the birth of our planet bombardment of Earth by objects from space has
been occurring. Such impacts have been linked to the extinction of many species,
including the dinosaurs. The risk of impact from asteroids, comets, and meteoroids
continues today. During the formation of earth comets, asteroids, meteoroids and
meteorites shaped and sized it. Water is believed to be brought to earth by comets as they
contain ice. Different elements like iron, nickel and other radioactive elements are
similarly brought to earth by these extraterrestrial objects. These objects can cause a lot
of damage and can destroy our planet completely if their size is big enough. In earth’s
history there are number of catastrophic events caused by the extraterrestrial objects.
THE TUNGUSKA EVENT:
On June 30, 1908, shortly after 7 A.M., witnesses in Siberia reported observing a
blue-white fireball with a glowing tail descending from the sky. The fireball exploded
above the Tunguska River Valley in a heavily forested, sparsely inhabited area. A statement
from a Farmer named Sergei Semenov who saw this incident.
“I was sitting in the porch of the house at the trading station of Vanovara at 7 a.m.
and looking towards the north . . . suddenly the sky appeared like it was split in two, high
above the forest, the whole northern sky appeared to be completely covered with blazing
fire. At that moment I felt a great wave of heat as if my shirt had caught fire… after a
minute, there was a loud bang in the sky, and I could hear a mighty crash. Subsequently, I
was fiercely thrown to the ground about 5-6 meters away from the house and for a minute
or two I lost my consciousness.”
Other witnesses a few tens of kilometers from the explosion reported that they were
physically blown into the air and knocked unconscious, they woke and saw a transformed
landscape of smoke and burning trees that had been blasted to the ground. Though there
were few witnesses close to the event, the sounds from the explosion were heard hundreds
of kilometers away, and the blast wave was recorded at meteorological recording sites
throughout Europe. This incident caused explosion just like a nuclear bomb and it was
many times more destructive than the bomb dropped on Hiroshima. Luckily the area was
inhabited so no official causalities happened, but it flattened a large area which was covered

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with trees killing all the habitats living in them. It is largest extraterrestrial object impact
event ever recorded in human history.
A photograph of trees destroyed in Tunguska event. Credit: the Leonid Kulik Expedition
At the time of explosion Russia was not politically stable and there was strife of
power in that region. So no team of scientists was sent to investigate the event. Finally in
1924, geologists who were working in the region interviewed surviving witnesses and
determined that the blast from the explosion was probably heard over an area of at least 1
million km2 (386,000 mi2 ) and that the fireball had been witnessed by hundreds of people.
Russian scientists went into the area in 1927, expecting to find an impact crater produced
by the extraterrestrial object that had apparently struck the area. Surprisingly they found
no crater, leading them to conclude that the destruction had been exploded in air and did
not impacted the earth.

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Over a hundred years later researchers are still asking questions about what exactly
took place on that fateful day. Many are convinced that it was an asteroid or a comet that was
responsible for the blast. But very few traces of this large extraterrestrial object have ever
been found, opening the way for more outlandish explanations for the explosion.
Recorded Impacts and Effects:
The site of the explosion was first investigated from 1927 to 1930 led by Russian
scientist Leonid Kulik. Russian scientist have confident that the destruction has been
caused by a giant meteorite impact. He persuaded Soviet government to send an expedition
to that area to find the remains and fragments of the meteorite, so that they can use it in
Soviet industries.
A visualization of Tunguska explosion event.
Around the epicenter (the location on the ground directly below the explosion)
Kulik found destroyed trees lying radially over an area of 15–30 km (10–20 miles).

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Everything had been devastated and scorched, and very little was growing occurred even
two decades after the event. The epicenter was easy to pinpoint because the felled trees all
pointed away from it, at that spot investigators observed a marshy bog but no crater. This
led to conclusion that the extraterrestrial object did not impacted the earth rather it exploded
in the air at elevation of about 7 km (4.3 mi).
Soviets performed experiments in the mid-1960s, in forests using small explosives
to produce butterfly-shaped blast patterns similar to the pattern found at the Tunguska site.
The experiments suggested that the object had approached at an angle of roughly 30
degrees from the ground and 115 degrees from north and had exploded in mid-air.
Eyewitnesses who had observed the event from a distance spoke of a fireball
lighting the horizon, followed by trembling ground and hot winds strong enough to throw
people down and shake buildings as in an earthquake. At the time, seismographs in Western
Europe recorded seismic waves from the blast. The blast had been initially visible from
about 800 km away, and because the object vaporized, gases were dispersed into the
atmosphere, thus causing the abnormally bright nighttime skies in Siberia and Europe for
some time after the event. Additional on-site investigations were performed by Soviet
scientists in 1958 through 1961 and by an Italian-Russian expedition in 1999.
Calculations show that the explosion had the force of 10 megatons of TNT,
equivalent to 10 hydrogen bombs. It is about 185 times more energy than the Hiroshima
atomic bomb, some estimates coming in even higher. But as it was not a nuclear bomb so
there were no after effects of radioactive decay in the region. Although tremendous air blast
caused more than 2,000 km2 (770 mi2) of forest to be flattened. Later calculations estimated
the size of the object responsible for the explosion to be about 50 to 100 m (150 to 300 ft.)
in diameter. It was most likely composed of relatively friable (easy to crumble) stony
material, that is why there are not much evidence material present.
The people of Earth were lucky that the Tunguska event occurred in a sparsely
populated, forested region. If the blast had occurred over a city such as London, Paris, or
Tokyo, then lives of millions of people would have been lost. Tunguska-type events are
thought to have recurrence interval of 1,000 years. A widely reported near miss of a
potentially dangerous asteroid occurred in March 2004.

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Mystery of Exploding Object:
There are literally trillions of particles in our solar system, ranging in size from dust
(millimeter) to larger bodies such as asteroids about 10 m (32 ft.) to 1,000 km (621 mi) in
diameter. Scientists which investigated the event were not on same page that what exactly
impacted or whether it impacted or not. Studies showed that there was sign of impact and
led to believe that object exploded in the air. Then there was confusion that what was this
object, whether it was a comet or an asteroid.
Asteroids are found in the asteroid belt, which is a region between Mars and Jupiter
or one belt is beyond Neptune, known as Kuiper Belt. The asteroids pose no threat to Earth
if they remain in the asteroid belt. But they move and collide, and a number of them are
now in orbits that intersect Earth’s orbit. When asteroids break into smaller particles they
are known as meteoroids. When a meteoroid enters Earth’s atmosphere, it is called meteor,
sometimes called shooting star due to light produced by frictional heating. If an asteroid
actually impact the earth surface then it is called meteorite. The comets also sometimes
enter the Earth’s orbit, it consists of frozen water and carbon dioxide plus rock fragments.
Table showing the difference between asteroid, comets etc.

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Idealized picture of a meteoroid entering the earth atmosphere.
In 1930, the British astronomer F.J.W. Whipple suggested that the Tunguska body
was a small comet. As comet is composed of dust and volatiles (water ice and frozen gases)
and could have been completely vaporized by the impact with Earth's atmosphere, without
impacting the surface, hence leaving no obvious traces. The comet hypothesis was further
supported by the glowing skies (or "sky glows" or "bright nights") observed across Europe
for several evenings after the impact, possibly explained by dust and ice that had been
dispersed from the comet's tail across the upper atmosphere. The cometary hypothesis
gained a general acceptance amongst Soviet Tunguska investigators by the 1960s.
In 1978, Slovak astronomer Ľubor Kresák suggested that the body was a fragment
of Comet Encke. This is a periodic comet with an extremely short period of 3 years that

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stays entirely within the orbit of Jupiter. It is also responsible for the Beta Taurids, which
is an annual meteor shower with activity around 28–29 June. The Tunguska event
coincided with the peak activity of that shower, and the approximate trajectory of the
Tunguska object is consistent with what would be expected from a fragment of Comet
Encke. It is now known that bodies of this kind explode at frequent intervals tens to
hundreds of kilometers above the ground. Military satellites have been observing these
explosions for decades.
In 1983, astronomer Zdeněk Sekanina published a paper criticizing the comet
hypothesis. He pointed out that a body composed of cometary material, travelling through
the atmosphere along such a shallow trajectory, ought to have disintegrated, whereas the
Tunguska body apparently remained intact into the lower atmosphere. He further argued
that the body was a dense, rocky object, probably of asteroidal origin. This hypothesis was
further boosted in 2001, when Farinella, Foschini released a study calculating the
probabilities based on orbital modelling extracted from the atmospheric trajectories of the
Tunguska object. They concluded with a probability of 83% that the object moved on an
asteroidal path originating from the asteroid belt, rather than on a cometary one (probability
of 17%).
The chief difficulty in the asteroid hypothesis is that a stony object should have
produced a large crater where it struck the ground, but no such crater has been found. It
has been hypothesized that the passage of the asteroid through the atmosphere caused
pressures and temperatures to build up to a point where the asteroid abruptly disintegrated
in a huge explosion. The destruction would have to have been so complete that no remnants
of substantial size survived, and the material scattered into the upper atmosphere during
the explosion would have caused the sky glows.
Many scientists and expedition teams visited the site again to find out whether it
was a comet or an asteroid. They used more advance techniques and equipment for more
precise calculation. They found evidence to support both theories but not all agree on one
theory. Some believe it was a comet while other believe it was an asteroid. There is still
work going on to find out that object impacted or not to determine whether it was a comet
or an asteroid.

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Conspiracies Theories:
Wilder theories have been made about over the years regarding what caused the
Tunguska explosion, some of which are:
 A UFO crash, due to the similarity of Tunguska and Hiroshima, a science fiction
writer named Alexander Kazantsev wrote a story in which the Tunguska event was
the exploding nuclear power plant of a spaceship from Mars. A few Russian
scientists took up the cause and claimed to find various bits of evidence, but they
were not able to give solid evidence for a civilized alien spaceship crash.
 The annihilation of a chunk of antimatter from space. According to many so-called
“experts”, Tunguska explosion was supposed to be caused by annihilation.
Annihilation is a physical process that occurs when a subatomic particle collides
with its respective antiparticle of the opposite charge, producing immense amounts
of energy. According to this theory, first suggested by Lincoln LaPaz in 1941, the
Tunguska event was likely caused by the annihilation of a chunk of
antimatter colliding with Earth. Although the antimatter theory explains the
observed luminous phenomena, and why no remnants of asteroid or comet were
found in the area, existence of such large antimatter chunks is often deemed being
theoretically impossible. Moreover, annihilation of the alleged chunk of antimatter
would probably happen in the uppermost atmospheric levels.
 Another speculative hypothesis suggests, that the 1908 Tunguska explosion was
caused by a small black hole passing through Earth. This hypothesis was first given
by American scientists Albert A. Jackson and Michael P. Ryan in 1973. However,
as there was no exit event (second explosion, occurring as the black hole shot out
in the North Atlantic), this hypothesis is considered wrong by majority of modern
scientists. Other evidence, as dust trails and high-nickel concentrations around the
impact area also dismiss this hypothesis.
 Nikola Tesla was the man who pioneered radio and modern alternating current
electric power (AC) systems, but sometimes seem as a mad scientist. One story
alleges he test-fired a death ray on the evening of June 30, 1908, and once he found

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out about the Tunguska event, he dismantled the weapon, considering it too
dangerous to remain in existence.
 A geophysical hypotheses was given by Astrophysicist Wolfgang Kundt at the
University of Bonn in Germany and others, that an eruption of natural gas from
kimberlite, a volcanic rock best known for sometimes holding diamonds, caused
the explosion. He suggested that material would have come from the molten earth,
some 3,000 kilometers deep (1,864 miles), the natural gas would be stored as a fluid
that deep, and when it reaches the surface it would become a gas and expand by a
factor of thousand in volume, for a huge explosion. He used the pattern the trees
fell in, as well as chemical anomalies to support his theory.
Seeing and hearing about all these hypotheses and theories a renowned American
geophysicist named Mark Boslough said.
"Lots of theories are going to pop up, it's like a crime scene, and everyone wants to
have a hand in solving the mystery, it's fun to speculate."
If we rule out crashed spacecraft, black holes, antimatter particles and geophysical
explosions as causes of the Tunguska event, the only phenomena which explain the event
is that either it was a comet or an asteroid. Although it is widely believed that event was
caused by an asteroid or comet but scientists are still trying to find what actually happened.
Risk Related to Impact:
The risk of an event is related to both the probability of an event occurring and the
consequences if it occurs. The consequences of aerial bursts or direct impact from
extraterrestrial objects several kilometers in diameter would be catastrophic. Although 7
out of 10 such events would likely occur in the oceans, still results would be felt worldwide
because of the enormous size of the object. Certainly there would be significant differences,
depending on the site of impact and size of the, but the overall consequences would
constitute a global catastrophe with high potential for mass extinction. Such events
probably occur on Earth with recurrence interval of tens to hundreds of millions of years.
Smaller objects of size few tens of meters will produce an aerial blast or cause an impact
crater, it would produce a regional catastrophe if the event occurred on land near a

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populated area. The size of the area devastated would be on the order of several thousand
square kilometers and could cause millions of deaths if the event occurred in an urbanized
region. We term these smaller but regionally significant events “Tunguska-type” events. A
recent study that evaluated aerial blasts from asteroids with diameters of about 50 to 100
m suggests that asteroids that are capable of causing catastrophic damages to a region occur
on average about every 1,000 years. Using the Tunguska event as a characteristic event
with a hit every thousand years somewhere on Earth, an urban area is likely to be destroyed
every few tens of thousands of years. There is tremendous statistical variability in trying to
predict the likelihood and type of future impacts, and when such estimates are made, the
death tolls over a typical century may range from zero to as high as several hundred
thousand. A truly catastrophic event could kill millions of people. According to the
probabilities and statistical data, it appears that the risk of dying from a large impact or
aerial blast from a comet or asteroid is considerably greater than other risks we normally
face in life. But the risks related to impacts are spread out over thousands of years.
Minimizing the Impact:
 Programs Launched:
Identification and categorization of comets and asteroids that cross Earth’s orbit are
already in progress. Size of Extraterrestrial Objects vary, it can be diameters less than 50
m (164 ft.), 50 m to several hundred meters, and diameter of several kilometers. A program
known as Spacewatch, which has been operating since 1981, is attempting to take inventory
of the region surrounding Earth with expansion to the entire solar system.
Based on the inventory data, scientists believe that there are around 135,000 objects
with a diameter of 100 m (328 ft.) or less that are Earth-crossing asteroids. Another
program, known as the NEAT (Near-Earth Asteroid Tracking) system, began in 1996. The
objective of this program, supported by the National Aeronautics and Space Administration
(NASA), is to study the size distribution and dynamic processes associated with near-Earth
objects and specifically to identify those objects with a diameter of about 1 km (3,280 ft.).
Both observation programs utilize cameras and telescopes. Images are analyzed to identify
fast-moving objects.

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The programs and systems to identify near-Earth objects are expected to intensify
in the future, and more objects will be cataloged. This is a first step toward evaluating the
potential hazard from near-Earth objects. However, evaluation will take a long time
because many of the objects have orbits that may not bring them close to Earth for decades,
and the average amount of time between potentially catastrophic impacts is at least
thousands of years for the smallest objects.
The good news is that most of the objects considered hazardous to Earth will likely
not collide with our planet until several thousand years after they have been discovered.
Therefore, we will have an extended period of time to learn about a particular
extraterrestrial object and to attempt to develop appropriate technology to minimize the
hazard.
 Techniques to Avoid Impact:
Once it has been determined that a large near Earth object is on a collision path
with our planet, options available to avoid or minimize the hazard from an aerial burst or
crater-forming event are limited. In the event of a large comet or asteroid colliding with
Earth, there will be no place in which to escape on the planet. Living things, including
people, within the blast area will be killed immediately, those further away are likely to be
killed due to the after effects like: from the cold and the destruction of the food chain. Even
if we could identify and intercept the object, blowing it apart into smaller pieces would
likely cause more damage than the impact from the larger body because each of the smaller
pieces would rain on Earth.
A more thoughtful approach would be to try to gently divert the object so that it
misses Earth. For a body that has been crossing Earth’s orbit for millions of years without
an impact, if it change its orbit, it would miss rather than strike Earth. There is a 99 percent
probability that we would identify the object at least 100 years before impact. We have the
potential technology to change the orbit of a threatening asteroid with small nuclear
explosions that are close enough to the asteroid to nudge it but far enough away to avoid
breaking it up. To complete this mission would require cooperation among the world’s
militaries and space agencies. The cost of such an expedition would likely exceed $1

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billion. However, it would be a small price to pay considering the potential damages from
a Tunguska-type event if it were to occur in an urban area.
Another option for smaller events might be evacuation. If we could predict
precisely where the event would occur months in advance, evacuation is theoretically
possible. However, evacuating an area of several thousand square kilometers would be a
tremendous, if not impossible.
Why Choose This Topic:
Our planet, which is our only place to stay is in constant danger from the outside
objects. It has been under attack of extraterrestrial objects in its history. Outside objects
has killed and extinct many species on our planet from smaller to large.
For us to save ourselves from these objects, which poses a great danger to our
existence, we have to be aware of them. We should know how these objects revolve in
orbits around our planet. How they have affected in the past and when they will again
impact the ground. We have to develop techniques to save ourselves if they ever pose a
direct threat to our existence.
Suggestions:
Here are few suggestions which we can adapt to avoid destruction from the
extraterrestrial objects:
 Develop better techniques and start different projects to study the pattern of space
objects. It would involve making different departments which study different
phenomena or specific field individually.
 Launch more space programs and make observatories to study how these objects
are affecting other planets.
 Create weapons and instruments which can deflect the object if it is in an orbit
which might cause impact.
 Educate people and especially children so they enter the field of astronomy.
 Keep looking for alternative habitat able planets.

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 Create better evacuation plans and recovery techniques if not very large scale object
is about to impact with earth.
 Create laser guns which disintegrate the foreign objects in to dust.
 Find more about the earth’s history to find whether life has been ever destroyed by
foreign objects, if yes then how life survived on the planet.

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Conclusion:
Our planet history is full of interesting events and phenomena, at some age there
was growth of life and at some age almost all life on planet extinct. Same is going to happen
in the year future, either climate of our planet will change completely killing all humans or
a large alien object might vanish us from the face of earth, who knows what is going to
happen. To save ourselves from extinction we need to take some measures, we need to
study planet’s history as well as what will happen in the near future. Space is full of objects
of different size which from time to time enter the earth’s atmosphere and some even
impacted, causing catastrophic changes. We have to develop tools and have knowledge
that how we can save ourselves if some object again try to erase life on the planet. If we do
not try something, then we are doomed and no alien will race is coming to save us.

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References:
Edward A. Keller, Introduction to Environmental Geology, Chapter 12, Pearson Education
Publisher, New Jersey, Fifth Edition
https://en.wikipedia.org/wiki/Tunguska_event
http://earthsky.org/space/what-is-the-tunguska-explosion
https://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska
https://www.britannica.com/event/Tunguska-event
http://www.bbc.com/earth/story/20160706-in-siberia-in-1908-a-huge-explosion-came-
out-of-nowhere
http://www.historyrundown.com/4-most-ridiculous-theories-about-the-tunguska-event/
https://sputniknews.com/science/201701181049718416-tunguska-event-lake-cheko/