Cosmic Catastrophes
Transcript of Cosmic Catastrophes
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Cosmic Catastrophes-
Science Fiction or Reality?by Dr. Thomas Grollmann
Reprintedfro
m
TopicsNo.11
June 2003
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An asteroid measuring 50 meters in
diameter hurtles towards the earth at a
speed in excess of 55,000 kilometers per
hour. The object approaches the earth
from the side illuminated by the sun and
therefore aviods detection by any obser-
vatories on account of its apparently
stationary orbit. Friction with the atmos-
phere rapidly heats the object so
vigorously that it begins to glow morebrightly than the sun. It passes almost
silently through the atmosphere, accom-
panied by intense thermal radiation.
Electronic control systems for railways,
industrial facilities and computers are
severely disrupted. The bow wave cre-
ated in front of the object decelerates it
so sharply that shortly thereafter it ex-
plodes in the air with the force of 1,000
Dr. Thomas Grollmann
is a geophysicist with a
special interest in the
atmosphere and climate
issues. He has been with
GeneralCologne Re for10 years as an expert in
the field of natural haz-
ards and has led the Cat
Modeling team within the
Cat Center of Excellence
since 2001. The primary
focus of his work is on
developing and checking
the plausibility of models
for the natural hazards of
earthquake, windstorm
and flood in order to
determine the potentiallosses and average re-
quired risk premium per
year on a worldwide basis.
In this paper, he discusses
a hazard that has still to
be modeled but which
entails a considerable loss
potential.
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Hiroshima bombs - little remains other
than gas and dust. The flash of light can
be seen over a radius of 1,000 kilome-
ters.
The heat wave is so powerful that people
on the ground feel as if they are being
burned alive. The air-pressure wave
caused by the explosion hits shortly af-
terwards - first a deafening bang, then a
burning hurricane that sweeps away
everything in its path. Forests are left in
flames, gas stations explode, everything
within a radius of 30 kilometers is incin-
erated. The next air-pressure wave extin-
guishes the bulk of the fires but also
snaps trees, blows out windows and
doors, and indeed flattens entire houses.
Since the shock wave spreads more
quickly through the ground, it is her-
alded by minor earth tremors. Power
supplies and communication channels
are cut. Several thousand deaths are
reported, more than 100,000 people are
left injured and over 2,000 square kilo-
meters of urban land and forest are dev-
astated- an area twice the size of Berlin.
Science fiction or reality?In a way, both. Although the probabil-
ity of such an event occurring over a
major city is undoubtedly small, the
possibility of an object of this size
impacting somewhere on earth is
greater than generally assumed.
Many such impacts have occurred in
the past, one of the most well known
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being the asteroid strike in the Siberian
taiga in 1908. Survivors of that disaster
described a scenario similar to the one
outlined above. The aftereffects could be
seen locally for years, indeed decades,
afterwards.
So are meteorite strikes a real risk, and
is this another hitherto unrecognized
hazard like the terrorist attacks of Sep-
tember 11? Is there evidence of historical
impacts on earth, and if so, how are weto imagine such events might unfold?
How can we prepare for them, and what
steps should we take to avoid being
caught by surprise the next time?
Before considering these questions, let
us first shed some light on the origin
of the intruders, their prevalence, the
effects they have on the earth and
ultimately the consequences for the
insurance industry.
Comets and TheirComposition
Comets are chunks of ice thatconsist primarily of water ice,frozen gases, dust and carboncompounds - hence the fre-quently used description of adirty snowball. They are be-lieved to originate in an area inthe outer solar system betweenUranus and Neptune. Hot gases
moving outwards can cool hereand form solid bodies. As theplanets formed, these objectswere pushed outwards by the
force of gravity and are now lo-cated in the so-called OortCloud. When its path is dis-rupted by other stars, a cometcan leave its original orbit andcrash inwards onto a planet,such as the earth. As the cometdraws closer to the sun, solarradiation heats up the cometssurface and some of the ice va-porizes -giving rise to the tail.Depending on their orbit dura-
tions, comets are divided intoshort-period- less than 200years - and long-period comets
- more than 200 years to severalmillion years. The comets movein elliptical orbits around thesun, short-period comets in thesame plane as the planets andlong-period comets on anypath. The total number ofcomets in the Oort Cloud isestimated to be 100 billion, ofwhich at least one million canreach the inner solar system.Due to the considerable dis-
tance, it is impossible to deter-mine how large the objects inthe Oort Cloud are. A further
comet reservoir located outsideNeptunes orbit, the Edgeworth-Kuiper Belt, is named after twoplanetary researchers. Objectswith a diameter of 200 -400 kilo-meters have occasionally beenobserved there. The comets inthis belt are difficult to discoversince the sunlight is too weak tovaporize the ice on account ofthe vast distance.
Asteroid belt. Located
between Mars and Jupiter,
the asteroid belt is a dense
cloud of around 50 million
objects (above).
The comet Kudo-Fujikawa
passing in early 2003.
GeneralCologne Re4
Earth
Mars
Venus
SunMercury
January 12, 2003
January 16
January 20
January 24
January 28
February 1, 2003
February 5
February 9
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Origin and Classification ofExtraterrestrial Objects
Approximately 4.6 billion years ago, the
compression of an original cloud of gas
and dust gave birth to our solar system.
Collisions between the first bodies of
solid rock ultimately caused the planets
and their moons to form. Yet some frag-
ments of rock were left behind to find
another destiny - not as planets or
moons, but as comets and asteroids.
Celestial phenomena such as comets
were long regarded as messengers of the
gods or as part of the planetary system.
As long ago as 1695, however, the plane-
tary scientist Edmond Halley realized
that comets orbit the sun - Halleys
Comet, named after him, was correctly
identified as having a return period of
76 years. Initially, the search for further
planets and comets was restricted to the
orbit parameters specified by Newton in
his theory of gravitation. In this way, it
was possible on the basis of disturbances
affecting already known planets to pre-
dict the existence of other planets - the
planet Uranus, for example - which
were only discovered years later. It is
only in the last 50 years that comets have
been systematically traced and cata-
loged.
Many comets are to be found in theso-called Oort Cloud - a comet reservoir
that came into existence after the planets
were formed. Located in the outer solar
system, it forms a spherical cloud around
the sun. The Edgeworth-Kuiper Belt, an-
other comet reservoir named after two
planetary scientists, is located outside
the orbit of Neptune. Individual objects
with a diameter of 200-400 kilometers
have occasionally been sighted there.
Comets in this belt are very difficult to
detect, however, because at this distance
the sunlight is too weak to vaporize the
ice.
Comets move around the sun in elliptical
orbits. Short-period comets with orbit
durations of less than 200 years move in
the same plane as the planets, but long-
period comets with return periods of
hundreds of thousands or even millions
of years come from every direction.Long-period comets are particularly
difficult to track, since they often remain
undiscovered due to their long orbit du-
rations and cannot be located until they
are in the vicinity of Jupiter. An impact
on the earth would then only be around
three to four more years away - short
notice for possible defensive measures.
Given the large number of objects, it is
virtually impossible with the tools cur-
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Asteroids
Asteroids, also known as smallplanets, planetoids or mete-oroids, have little ice contentcompared to comets, or evennone whatsoever. They are com-posed largely of rock with smallamounts of metals and carbons.A small proportion of asteroids,around 3%, is comprised almostentirely of metals, most com-
monly iron. The main belt inwhich asteroids orbit the sun onalmost circular paths is locatedbetween the planets Mars and
Jupiter. The total mass of theasteroids is less than one per milof the earths mass. Near-earthasteroids (NEOs) at a distance ofless than 7.5 million kilometersand with a diameter in excess of150 meters are categorized as po-tentially hazardous asteroids(PHAs), since disturbances intheir orbit could cause them tocome closer to the earth. Of thecurrently known 1,500 NEOs,
one-third are classed as PHAs.Objects smaller than 30 meters insize would burn up in the atmos-
phere and therefore pose no dan-ger. Of the estimated 50 millionobjects, only around 1,500 areknown to be earth-near.
Currently estimated number ofnear-earth asteroids:
Size Number
> 30 m > 50,000,000
> 100 m > 320,000
> 500 m > 9,200> 1,000 m > 2,100
> 2,000 m > 400
Earth Sun Mars Jupiter
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rently available to calculate in advance
the precise path of every comet and the
moment when each one will appear in
our solar system.
Yet there are also other objects too small
to be classified as planets. These are
known as asteroids, the largest of them
- Ceres - having a diameter of 931 kilo-
meters. Since these objects are too small
to be seen with the naked eye, they were
discovered relatively late, with the first
being identified in 1801. Asteroids con-
sist primarily of rock with metal and
carbon admixtures. Meteorites com-
posed of iron are found more rarely.
Today, more than 150,000 of these
mini-planets have been detected,
although the precise path of such aster-
oids is known in only about 20% of
cases. For the most part, these small
planets travel around the sun in near-
circular orbits in the so-called asteroid
belt between Mars and Jupiter- moving
in the same plane as the other planets.
Several asteroids intersect with the
earths orbit. These are referred to as
near-earth objects (NEOs). Others
which do not currently cross the earths
path could be nudged out of their origi-
nal orbit and crash into the earth. The
catastrophic scenario used in films,
whereby a comet hits an asteroid and
redirects it towards the earth, is pure fic-
tion, since such a collision would destroy
both objects. The largest of the more
than 400 currently known NEOs are
approximately eight kilometers in size,
while the vast majority of NEOs measure
between one and three kilometers.
The composition of meteorites differs
fundamentally from rocks found on
earth. During the long period they
spend travelling through space, mete-
orites are constantly bombarded by cos-
mic radiation. This gives rise to nuclear
reactions, which create a number of
isotopes with known half-lives. On this
basis, it is possible to determine how old
meteorites are. They range in age from
a few million years to 4.55 billion years,
the age of the earth.
Each year, approximately 40,000 tons of
micrometeorites fall to earth-
roughly
25% of the total extraterrestrial material
that reaches the earth on a long-term
annual average. This corresponds to
around 50,000 meteorites per year. In
other words, the earth is struck by mete-
orites very frequently.
Signs of Impact on the Earth
How can we distinguish between impact
craters and volcanic craters or other
crater-like formations? On the earth,
unlike on other planets, there are manyprocesses which in the long run cover
over the traces of an impact and indeed
render them unrecognizable: erosion,
sedimentation and continental drift.
In a relatively short space of time, erosion
due to water, wind, sandstorms, glacier
formation and temperature changes eats
away at exposed surfaces such as crater
rims and ultimately levels them off. Sedi-
mentation deposits the eroded material
in lower-lying areas inside or around the
rim of the crater, thus filling in the topo-
graphical irregularities. It is due to these
surface-changing processes on the earth
that, for example, small craters such as
the Meteor Crater in Arizona have be-
come virtually unrecognizable following
the erosion of 100-200 meters of rock.
The famous impact crater in Mexico,
which - based on our current knowl-
edge - is believed to have been caused
65 million years ago by an asteroid and
heralded the extinction of the dinosaurs,
could only be identified with certainty
using aerial photographs and subse-
quent seismic, magnetic and gravimetric
measurements.
An impact at sea can cause the formation
of craters that do not project up to the
oceans surface. If an asteroid is large
enough (>1 km), the object can pene-
trate the earths crust to a considerable
depth. This may induce instability in
the crust and cause volcanoes to form.
New islands are created at the impact
site, leaving the impact itself unde-
tectable. Even if there is no volcanic
activity, sedimentation covers over the
impact crater relatively quickly. In the
course of millions of years, continental
drift (also referred to as plate tectonics)
modifies the appearance of the earths
surface; the shape and structure of
craters are changed or entirely destroyedas entire plates disappear and dissolve
into the earths mantle, are distorted by
tectonic processes or are forced upwards
into mountain ranges as they collide
with one another. Identification of im-
pact craters is consequently no longer
possible.
Since it is clearly difficult to identify
craters on the earth, it is worth making
comparisons with other planets and
moons where the forces of erosion either
do not exist or are less severe. Virtuallyall the craters on the moon were caused
by impacts. Owing to the lack of an at-
mosphere, even the smallest fragments -
measuring just millimeters - crash into
the moons surface with a high velocity.
On the earth, such fragments would
burn up as shooting stars because of the
immense friction. Consequently, the
major processes involved in meteorite
impacts were studied first on the basis of
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the moon, before then looking for corre-
sponding patterns on the earth. It was
determined, for example, that practically
all the craters on the moon are circular.
This is attributable to the fact that an im-
pact resembles an explosion - given the
high speed with which the object hits -
and hence the craters are circular, irre-
spective of the angle of impact. Only
with a very shallow angle of impact canelliptical craters form.
Owing to the earths atmosphere, craters
here can only be created by projectiles in
excess of a certain size (>30 m). Yet even
from space, it is only possible to discern
a few of these craters, such as the
34-kilometer-wide West Clearwater
crater in Canada, the Nrdlinger Ries
crater in Germany and the Kara crater in
Pamir. Research into craters on earth has
revealed that in the course of its history,
it has been struck by numerous aster-
oids, yet the traces of the impacts have
been carried away by erosion or covered
over through sedimentation or the frag-ments burned up in the atmosphere if
they were too small. Frequency statistics
indicate that minor impacts are to be
expected relatively frequently, but large
impacts only very seldom. Explosions of
objects in the atmosphere were observed,
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Meteorites
Asteroids that can be seenfalling to earth in the nightsky are known as meteors (orshooting stars). Meteorites arethe remnants of asteroids thatcan be found on earth in theform of pieces of rock. Up to50,000 objects fall to earthevery year. Depending on theircomposition, meteorites aredivided into stony, stony-ironand iron meteorites. Accountingfor 97% of all meteorites, stonymeteorites are the most com-mon. A distinction is made herebetween chondrites with agrainy structure, carbonaceouschondrites with admixtures of
water and carbon, and achon-drites with an iron core. Thecarbonaceous chondrites areconsidered to be primary rocksthat reflect the very earliestphases of planet formation.The achondrites melted at aprimitive stage, producing aniron core. Stony-iron meteoritesare composed of a mixture ofiron and crystallized metals.Iron meteorites can be differen-tiated according to their admix-tures of other metals, e.g.nickel.
Meteorite impactson the moon
Undifferentiated
Agglomeration of dust fromthe solar nebula
Age: 4.55 bn years (oldestbodies in the solar system)
Differentiated
Melting, crystallization in theparent body
Age: < 4.5 bn years(e.g. Martian meteorites1 bn years)
Rough Classification of MeteoritesIron
meteoritesStony-ironmeteorites
Chondrites Achondrites
Stonymeteorites
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for example, in 1908 in Tunguska, Siberia,
1930 in Curuca, Brazil, and 1935 in
Rupununi, British Guyana.
Objective Criteria forIdentifying an Impact Crater
The effects of an impact on the earth
depend on numerous factors: the mass,
density, shape, solidity, size and speed of
the projectile, the angle of impact and
the impact site (land or water). Impactsby objects greater than one kilometer in
diameter are classified as catastrophic
events, although objects smaller than
this can also cause considerable damage.
Various criteria can be used to unam-
biguously identify a crater as an impact
site. Some simple characteristics, such as
a circular shape, central mountain peaks
in the
middle or in-
ner peripheral moun-
tains, do not serve to distinguish impact
craters from volcanic craters or collapsed
structures. Noncircular impact craters are
also found, where they have been de-
formed by tectonic forces or the impact
occurred at a very shallow angle - circu-
lar craters result from impact angles of
around 10-
90, while a glancing im-pact angle of less than 10 gives rise to
elliptical craters.
If the geological structure of the subsoil
in the region does not permit the forma-
tion of craters (no tectonic forces at work,
no volcanoes), this would indicate the
presence of an impact crater. Various
geophysical methods are used to investi-
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Isotopes and Rare Earths
Isotopes of an element aredistinguished by the number ofcomponents in their nucleus.The protons determine the ele-ment, the neutrons determinethe various modifications ofthe element, i.e. the isotopes.Isotopes play a significant rolein documenting variousprocesses. For example, thecarbon isotope 14C is used to
determine the age of tree ringsand sediment layers. Cosmo-chemistry frequently makes useof the elements of rare earths,e.g. osmium and iridium. Inmeteorites, certain isotopessuch as 188Os are enrichedwhen compared with terrestrialrock, i.e. their presence is10-100 times higher.
Meteorite fragments
found on earth
Impacts on the earth and
diameter of the craters
< 5
5-20
20-50
50-100
> 100 km diameter
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gate these anomalies, e.g. measure-
ments of the earths gravitational field or
the earths magnetic field or the propa-
gation pattern of artificially emitted seis-
mic waves. Yet even after the anomalies
have been identified, it cannot be certain
whether they were caused by an impact.
The next step is geological rock analysis.
The composition of meteorites differs
from that of the local rock. Often, how-
ever, meteorites vaporize in the air oron impact, leaving no consistent rock
remains. Upon impact, the substance of
the rock is also so greatly altered by the
extremely high pressures and tempera-
tures (metamorphosis) that only the exis-
tence of foreign minerals (e.g. diamond
or coesite and stishovite, high-pressure
modifications of quartz) can point to an
impact. The presence of stishovite is to-
The 10 Largest Known Impact Craters
Vredefort South Africa 27:00 S 27:30 E 300 2,023
Chicxulub Mexico, Yucatan 21:20 N 89:30 W 300 65
Sudbury Canada, Ontario 46:36 N 81:11 W 250 1,850
Popigai Russia 71:39 N 111:11 E 100 36
Manicougan Canada, Quebec 51:23 N 68:42 W 100 214
Acraman Australia 32:01 S 135:27 E 90 590Chesapeake Bay Crater USA, Virginia 37:17 N 76:01 W 90 36
Puchezh-Katunki Russia 56:58 N 43:43 E 80 167
Morokweng South Africa, Kalahari 26:28 S 23:32 E 70 145
Kara Russia 69:06 N 64:09 E 65 70
Crater Place/Region Position Diameter Age(km) (in million years)
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The Meteor Crater as
seen from space. Due to
its diameter of 32 kilome-
ters, this crater can beclearly seen in the upper
left half of the image.
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Number of Asteroids Classified According to Their Diameter
Number of asteroids
1,000
800
600
400
200
0
Diameter in meters
150 million/10 m
320,000/100m
9,200/500 m
2,100/1km
400/2km
10 100 1,000 10,000
day considered to be a highly reliable in-
dication of an impact, since this form of
quartz cannot occur on the earth under
natural conditions.
The last step in proving the existence of
an impact crater is to resort to geochem-
istry. The mixing ratios of rare elements
in the rock are compared. Certain ele-
ments are found far more commonly inmeteorites than they are on earth. If
analysis of the crater rock points to a sig-
nificantly high concentration of certain
rare elements, it is very likely that an im-
pact occurred. It is by no means unusual
for the differences to be measured in fac-
tors of 100 to 1,000. Isotopes - i.e. in ef-
fect the same elements but with a differ-
ent number of neutrons in the nucleus -
are used to improve accuracy. The iso-
tope composition of the meteorites is en-
tirely different to that of rocks in the
vicinity of the crater. If the composition
of the rock indicates that it came from a
meteorite, the presence of an impact
crater can definitively be determined.
Approximately 200 meteorite craters
have been identified to date, the majority
of them in the United States, Central
Europe and Australia. Around two to five
new craters are discovered every year.
The smallest of them are just a few
meters in diameter, the largest extend
up to 300 kilometers.
A theory to emerge in recent years sug-gests that large meteorites which hit the
ocean can penetrate so deeply into the
earths crust that they can cause a tear in
the mantle. This allows fresh magma to
flow upwards and can cause volcanoes
on the earths surface. This could explain
a number of so-called hot spots, i.e.
volcanoes not located at the edge of
plates. The earths crust melts at the
edges of the plates in the subduction
process and is carried to the earths sur-
face due to its lower density. This then
gives rise to familiar volcanoes such as
those in the so-called Ring of Fire around
the Pacific. In rare cases, however, volca-
noes are found away from the edges of
continental plates - something for which
11
1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
Trend in the Discovery of Near-Earth Asteroids from 1980 to 2000The number of asteroids identified has increased sharply, especially since 1998.
Number
Trend in the Discovery of Near-Earth Asteroids from 1980 to 2000The number of asteroids identified has increased sharply, especially since 1998.
Number
All near-earth asteroids
Large near-earth asteroids
Year
100,000,000
1,000,000
10,000
100
1
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a cogent explanation has hitherto been
lacking. According to the latest research,
Hawaii - as one of these hot spots -
could therefore have been created by
a meteorite impact.
What Happens upon Impact?
Asteroids enter the earths atmosphere at
a speed of 15-25 kilometers per second
(54,000-
90,000 km/h),whereas cometscan reach up to 70 kilometers per second
(252,000 km/h) if they crash head-on
into the earth. Depending on their mass
and velocity, these bodies are then
slowed to the normal speed of fall in the
atmosphere (around 200 km/h - the
speed with which a parachutist falls to
earth). Many meteorites lose the bulk of
their mass on entry into the earths
atmosphere as they melt and vaporize.
The atmosphere has the effect here of a
wall, suddenly decelerating objects sosharply that many of them are torn apart
in the air- they literally explode. Every
year, the earth is struck 20 -30 times by
fairly small objects which cause sizeable
explosions in the atmosphere, as was
the case, for example, in 1994 over the
South Pacific (explosive force roughly
a quarter that of the Hiroshima
bomb) and in 1990 over
Canada.
Yet the larger the asteroid, the less it is
slowed and hence the more speed it re-
tains. It becomes increasingly likely that
it will only be destroyed on impact. The
largest meteorite discovered on earth is
made of iron and measures 3x 3 meters.
It was found in northernNamibia. De-
spite its considerable weight, it pene-
trated to a depth of just two meters.
Meteorites composed of rock, on theother hand, break up more easily, which
is why no sizeable fragments have been
found.
During the contact and compression
phase, the projectile smashes into the
earths surface. If there were no atmos-
phere, there would be no prior interac-
tion between the projectile and the site
of impact. Owing to the presence of the
atmosphere, however, a cushion of air is
compressed ahead of the object, and
this then gives notice of the projectilesarrival at supersonic
speed. The very
rapid decel-
eration
gen-
erates shock waves, which cause the ma-
terial to suddenly melt and vaporize. The
pressures occurring here are around a
million times the pressure of the earths
atmosphere.
The ejection phase commences with the
explosive expansion of the rock at the
point of impact owing to the high pres-
sures and temperatures. A molten wave
of pulverized and vaporized material
spreads out from the point of impact
and may travel a very considerable dis-
tance before it falls to the ground again.
Displacement and ejection of the mate-
rial create a bowl-shaped crater that is
many times larger than the impact pro-
jectile. With large-impact craters, the
material can rise up into the stratosphere
or even ascend into the earths orbit,
only to fall back to earth over several
years. In the subsequent period, parts of
the rim of the freshly formed crater cavein and some of the material hurled up-
wards also settles back into the
crater, thereby filling it up.
Some of the most well-known
meteorite craters include the
Meteor Crater in Arizona, the Bo-
sumtwi Crater in West Africa and
the Nrdlinger Ries in Germany.
The Chicxulub Impact -the End of the Dinosaurs
As early as the 1970s, there was specula-
tion about the Cretaceous-Tertiary
boundary, the period when not only the
dinosaurs but also more than half of the
animal and plant species known at that
time died out. Of the remaining species,
too, many were drastically reduced in
number. This transitional phase can be
identified in many rock strata around the
world as the characteristic layer of clay
between the chalkstones of the Creta-
ceous and Tertiary periods (K/T bound-
Experts are now fairly
certain that 65 million
years ago, an asteroid
was the cause of the
dinosaurs extinction.
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ary). Here, too, an isotope anomaly was
found between the chalkstone strata
and the clay. Since this stratum had been
found in many areas of the world - with
isotope anomalies up to a factor of 200
- the theory of an asteroid impact arose
in the 1980s. Given the worldwide pres-
ence of this stratum, the impact must
have been extremely large. Subsequent
investigations then also unearthed largequantities of soot in the rock strata - an
indication of extensive forest fires. Evi-
dence was accumulating of an impact
of gigantic dimensions -yet where was
the crater?
At almost the same time, in the early
1980s, a major gravity anomaly was dis-
covered during a search for oil under the
Yucatan Peninsula in Mexico. For a long
time no further investigations were con-
ducted. Only in the early 1990s were
drilling samples taken and all the indica-tions of an impact crater confirmed,
despite the fact that absolutely no hint
of an impact could be detected on the
surface. Over the past millions of years,
the crater had been virtually entirely
covered over by sediments.Now all that
remained was to answer the questions:
how old is this crater, and could this
have been the notorious impact that
led to the extinction of the dinosaurs?
Investigations revealed that the crater
had a diameter of 300 kilometers and islocated partly below the Yucatan Penin-
sula and partly beneath the Gulf of
Mexico. It was thus of adequate dimen-
sions to produce worldwide effects.
Only its age remained to be determined.
Using two independent methods, the
age of the impact was determined to
be 65 million years - precisely the age
of the mysterious Cretaceous-Tertiary
boundary. Evidence had thus been fur-
nished for a cosmic event with dramatic
repercussions for fauna and flora.
Based on our insights today, this is what
is believed to have occurred:
An asteroid roughly 10 kilometers in
diameter approached the earth at a
speed of around 100,000 kilometers per
hour and passed through the atmos-
phere in a matter of seconds. The object
heated up and was briefly brighter and
warmer than the sun. The projectile bur-
rowed into the earths crust to a depth of
approximately 40 kilometers, but the
earths crust soaked up the impact like a
glutinous liquid. What remained was a
crater roughly 300 kilometers wide and
several kilometers deep. The object va-
porized instantly in a massive explosion.
The vaporized rocks released millions of
tons of dust, steam, carbon dioxide and
sulfur dioxide, darkening the sky for sev-
eral months and causing temperatures
to drop rapidly.
Earthquake waves of magnitude 12 on
the Richter scale spread out from the im-
pact site. The impact in shallow water
produced tsunamis with waves reaching
a height of 100 meters and more. Smol-
dering chunks of rock fell to the ground
tens of thousands of kilometers away
from the impact site, setting fire to
forests. Once the waves had subsided,
the worst was over. Still, the darkening
of the stratosphere resulting from the
immense quantities of dust caused tem-
peratures to fall, and the food chain col-lapsed as photosynthesis was disrupted.
The enormous quantities of carbon diox-
ide exacerbated the greenhouse effect in
the atmosphere and, once the dust had
settled, it became warmer for many
hundreds, indeed thousands, of years.
Ultimately around 75% of all animal and
plant species, including the dinosaurs,
died out. The plant and animal world
was unable to adapt to such abrupt
climate changes, and only a few species
survived the catastrophe.
Gravitational anomaly in
Yucatan and the Gulf of
Mexico. The crater structure
can be clearly made out.
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Impact Probabilities
For planetary researchers, 1994 was an
exceptional year. For the first time it was
possible to predict and ultimately ob-
serve the impact of comet fragments on
Jupiter. The skies are routinely scanned
for near-earth objects, and in 1993 a
bright string of pearls was discovered
that was ultimately identified as the
remains of the roughly four-kilometer-long, fragmented comet Shoemaker-
Levy 9. On the basis of the comets path,
it was calculated that these fragments
would impact Jupiter in 1994. When, in
1994, the pieces finally hit Jupiter, the
results of the impact of the largest frag-
ment, one to two kilometers in size,
could be clearly seen in the form of a
crater with a diameter of more than
10,000 kilometers. Further impacts fol-
lowed with comet fragments measuring
several hundred meters in diameter. Itwas thus proven that impacts can occur
anywhere in the solar system - with at
times dramatic effects.
The catastrophes described above in
Mexico and Siberia demonstrated that
catastrophic meteorite impacts have also
occurred on earth. The meteorite that
caused the Tunguska event is calculated
as having been 50 meters in diameter;
the Chicxulub object had a diameter of
10 kilometers. And in recent decades,
further asteroid explosions have beenobserved, one of them in 1990 at a
height of 30 kilometers above the
Pacific Ocean.
This raises the question of just how likely
meteorites of various sizes are to hit the
earth.
The following conclusions have been
reached, based on astronomical obser-
vations and studies of known impacts:
In statistical terms, a 50-meter asteroid
impacts somewhere on earth approxi-
mately every 250 years (corresponds to
the Tunguska explosion), a 200-meter
asteroid roughly every 5,000 years, a
one-kilometer-sized asteroid about every
100,000 years and a 10-kilometer-sized
asteroid - as was the case with the Chic-
xulub event- approximately every
20-
60 million years.
Needless to say, this does not mean that
after the impact of the Chicxulub aster-
oid, for example, it will be 50 million
years until the next such asteroid comes
along. (Since the impact occurred
65 million years ago, this would wrongly
imply that an impact today is highly
probable. This is not the case.) As with
storms, the average waiting period
is merely an arithmetic mean figure:
it is absolutely possible for a once-in-
a-100-year event to occur three timesin succession, followed by a gap of
300 years. In other words, an impact
can occur at any time - an entirely realis-
tic scenario in view of the large number
of potentially hazardous asteroids and
comets and the small number of objects
identified to date in space.
Most objects larger than one kilometer
are now known, but not all of them. Few
of the smaller objects (such as that which
caused the Tunguska event) are known.
Even fewer of the comets are known,since they have comparatively lengthy
orbit durations. Rough estimates suggest
that there are at least 200,000 bodies
with a diameter of several hundred
meters whose paths intersect with the
earths orbit. It is not enough simply to
identify them; considerable effort has
to be expended on determining their
orbits. If we were to discover 10 NEOs
per month, assuming the use of 150 tel-
In recent years the number of
near-earth objects discovered
has increased sharply.
Traces of the Tunguska
explosion could still be
discerned decades later.
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Heat and pressure wave Explosion, rain of dust and small rocks Tsunami
GeneralCologne Re16
quent pressure and heat waves will
claim a large number of lives. An impact
at sea would not produce any direct in-
juries or damage, but it would trigger a
tsunami that would reach coastal areas
with meter-high tidal waves. With more
than 70% of the planets surface covered
by water, the probability of an impact at
sea is relatively high.
The consequences for the insurance in-
dustry, however, would depend on the
size of the impacting object. This can be
illustrated on the basis of four different
sizes of object:
I Type I: Asteroid with a diameter of
0-30 meters
Roughly 10,000-50,000 meteorites
per year
I Type II: Asteroid 50 meters in dia-
meter (e.g. Tunguska event)
Probability of occurrence: approxi-
mately once in 250 yearsI Type III: Asteroid one kilometer in
diameter
Probability of occurrence: roughly
once in 100,000 years
I Type IV: Asteroid 10 kilometers in
diameter (e.g. Chicxulub event)
Probability of occurrence: roughly
once in 50 million years
The probabilities of occurrence refer to
an impact somewhere on earth, i.e. not
necessarily in an inhabited region. How-
ever, the chance of an asteroid comingdown somewhere over water or in an
uninhabited area is very high.
Type I asteroids are very common. They
fall from the sky as dust or small rock
fragments. As recently as March 27
of this year, a meteorite broke up into
several pieces over the U.S., and its frag-
ments crashed into several houses in the
form of chunks of rock the size of tennis
balls. While these objects can cause sig-
nificant damage to, or even the total de-
struction of, individual risks such as cars,
buildings or industrial risks, they do not
pose any appreciable accumulation risk.
Nor are further hazards such as heat
waves, earthquakes or tsunamis to be
expected.
Asteroids of Type II will most likely ex-
plode in the air. If this occurs over land,
the heat wave will ignite fires in the im-
mediate vicinity that can inflict direct
damage on forests, buildings and infra-
structure. The subsequent pressure wave
may extinguish such fires - but the struc-
tures will now be entirely demolished -
buildings can explode and trees will be
snapped like matches. Total destruction
should be assumed in the area closest to
the impact. Large cities such as Berlin orBoston would be very extensively de-
stroyed if they were to be hit. A rain of
small rocks and dust would cause con-
siderable damage. At greater distances,
little damage is to be expected. The loss
potential would surpass that of a major
earthquake in, say, San Francisco or
Tokyo. There would be no direct dam-
age if the asteroid exploded over the
ocean, but the tsunami could cause
considerable damage even at great dis-
tances. If such a meteorite were to hit the
Pacific, the tsunami would reach a height
of 10-15 meters and could penetrate sev-
eral hundred meters inland. Pacific Rim
cities located directly on the coast, such
as Tokyo, Vancouver and Los Angeles,
would suffer substantial damage, de-
pending on their distance from the point
of impact.
Larger asteroids of Type III will generally
impact the earths surface. On land, a
crater around 20 kilometers in diameter
would be created. Major cities such as
New York, Tokyo or Berlin would be
completely destroyed. Very heavy dam-
age would be incurred within a radius of
500 kilometers (corresponding to the
size of a small U.S. state or a federal state
in Germany). Forest fires would rageacross an area the size of an entire conti-
nent. A regional climate change has a
considerable impact on flora and fauna.
In the event of an impact at sea, large
masses of water would be hurled more
than 10 kilometers into the air. The re-
sulting tsunami would lose momentum
very quickly, but even at a distance of
1,000 kilometers, wave amplitudes of
several hundred meters would be
reached. Cities like Los Angeles, Tokyo,
Hong Kong or Miami would be totally
destroyed, with just a few ruins of rein-
forced concrete left standing.
Asteroids of Type IV have global conse-
quences. On land - the impact crater
would measure roughly 300 kilometers
across - entire continents would be de-
stroyed. The damage can scarcely be
quantified, since fallingchunks of molten
rock would ignite fires on a worldwide
scale, burning down buildings and
forests. Earthquake waves measuring 12
on the Richter scale would be unleashed.
Other global repercussions would follow
due to forest fires and the associated
release of aerosols (cooling - cosmic
winter), the increased greenhouse ef-
fect caused by higher emissions of car-
bon dioxide, the release of sulfur dioxide
and the related acid rain (risk of corro-
sion), the destruction of the ozone layer
Hazards Associated with Meteorites
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Hurling of water to a high altitude and
release of water steam due to the intense heat
Release of gases from the vaporization of rocks,
e.g. carbon dioxide, sulfur dioxide, nitric oxides Earthquake
17
(worsened effects of hard UV rays,
increased risk of cancer), radioactive
contamination following the destruction
of atomic power plants and nuclear
weapons stores and chemical contami-
nation caused by chemical risks. The
food supply for humans and animals
would be under acute threat. It is doubt-
ful whether flora and fauna could adapt
to such a dramatic climate change. Cer-tainly, the dinosaurs and many other
species of animals and plants were un-
able to cope with such changes some
65 million years ago.
Insurance Considerations
For the insurance industry, asteroids of
Types I and II are important because
of their high probability of occurrence,
and Type II all the more so owing to the
potential accumulation risk. It should be
reiterated that while the likelihood of a
Type II asteroid impacting close to a ma-
jor metropolitan center is extraordinarily
low owing to the small area concerned
relative to the total area of the earths
surface, such an impact can nevertheless
occur at any time.
There are various hazards that may be of
relevance to insurers in the event of cos-
mic impacts, since they are applicable to
the vast majority of policies: rockfall, fire,
explosion, earthquake and tsunami. The
fire and explosion hazards are generally
covered, while protection against the
other hazards can only be obtained by
taking out appropriate supplementary
coverage. It is not always clear, however,
whether meteorite impacts are included
as a trigger. A fundamental distinction
must be made between all-risks policies
and policies with named perils. Under
Number of Objects and Their Mean Frequency
Number Return periodin years
Diameter in meters
Meteor Crater
Tunguska event
Chicxulub event
Global consequences
Number
Return period
100,000,000
10,000,000
1,000,000
100,000
10,000
1,000
100
10
1
100,000,000
10,000,000
1,000,000
100,000
10,000
1,000
100
10
1
0 100 1,000 10,000
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all-risks policies, coverage initially ex-
tends to all risks except those that are
explicitly excluded. Under named perils
policies, coverage extends only to the
specified perils, whereas all others are in
principle excluded.
Policies with named perils frequently
only refer to the impact of manned
flying objects as a covered risk - where
this risk is mentioned at all. In this case,direct losses and damage caused by
meteorite strikes (rockfall only) are ex-
cluded. On the other hand, the fire and
explosion risks as a consequence of a
meteorite impact are covered, since with
these perils the cause is immaterial. The
earthquake and tsunami risks are also
covered if supplementary coverage was
agreed for these perils. Here, too, the
cause is irrelevant. However, individual
policies may contain endorsements or
amendments that can lead to coverage
of meteorite strikes.
The existence of coverage under all-risks
policies must generally be assumed,
since falling/flying objects and
meteorites are not normally explicitly
named. Even if damage caused by
manned and unmanned flying objects
GeneralCologne Re18
The meteorite approaches the
earth.
Simulation of a meteorite impact(Sandia National Laboratories, USA)
The fragments impact the
earth. A crater forms.
Pieces of rock and dust are
hurled upwards into the
atmosphere.
The meteorite explodes in
the stratosphere and leaves
behind a vacuum channel.
3km
Diameter Effects
< 30 meters Object will not normally reach the earths surface.
75 meters Iron meteorites create craters up to a diameter of onekilometer; stony meteorites explode in the air, cause aheat and pressure wave as in the case of the Tunguskadisaster, and can completely destroy a city.
200 meters Impact on land destroys a major city such as New York
or Tokyo.
350 meters Impact on land destroys an area as large as a small coun-try; impact in the ocean causes moderate tsunamis.
750 meters Impact on land destroys an area as large as a medium-sized country; impact in the ocean causes severetsunamis that can devastate numerous coastal cities.
2,000 meters Impact on land hurls large masses of dust and watersteam into the upper atmosphere, has global repercus-sions due to climate change, and destroys an area thesize of a large country or U.S. state, e.g. France orCalifornia.
10,000 meters Global repercussions due to falling chunks of burningrock, forest fires on a worldwide scale; destroys an areathe size of several countries, threatens the survival of allfauna and flora, including mankind.
Effects of Meteorite Impacts According to Their Size
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is excluded, meteorites may be covered
since unmanned flying objects can -
depending on court practice - be inter-
preted as referring only to artificial, i.e.
man-made objects. Here, too, damage
caused by fire and explosion as a conse-
quence of meteorite impacts is covered,
since the cause is immaterial. The same
is true of earthquakes and tsunamis
unless such perils are explicitly excluded.
One exception would be countries such
as Spain where natural perils and mete-
orite impacts are covered by the state.
Cosmic catastrophes constitute a real
risk. At once in 250 years, the probability
of a Type II impact occurring somewhere
on the earth can no longer be ignored.
Of course, it is highly likely that these
objects will come down somewhere in
an uninhabited area or in the ocean at
a considerable distance from inhabited
coastal regions. But things may work out
very differently, since a meteorite strike
can occur anywhere at any time.
What we are describing here, then, is a
risk that is coveredunder numerous stan-
dard insurance policies but for which no
adequate risk assessment is performed.
The premium does not include any pric-
ing elements for this risk, no accumula-
tion control is carried out, and the policy
wordings make no clear differentiation
between hazards. Although it is ex-
tremely difficult to determine the precise
frequency of impacts broken down by
region and to estimate the potential
losses, it is undoubtedly necessary as a
first step to examine this aspect more
closely in the policy wordings and,
where appropriate, to clarify what is cov-
ered and what cannot in fact be covered.
This issue thus offers a parallel to the
events of September 11, when a loss
potential emerged that had previously
been inadequately assessed and con-
trolled. Could this be another risk from
the realms of the impossible or unimag-
inable?
19
10km
30km
100 km
Scenario for an impact over a
large city. Even though the possi-
bility of an explosion occurring
right over a major city is very re-
mote, the illustration is intended
to show the effect of a Tunguska-
sized impact (object 50 meters in
diameter) on a major metropoli-
tan center. The inner circle indi-
cates the area of total destruction.
The second circle shows the area
with considerable damage due to
the heat and pressure wave. The
third circle shows the area with
scattered damage.
Paris TokyoSan Francisco
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This information was compiled by GeneralCologne Re and is intended to provide background information to our clients, as well as to our
f i l t ff Th i f ti i ti iti d d t b i d d d t d i di ll It i t i t d d t b l l
Klnische Rckversicherungs-Gesellschaft AG, 2003