Cosmic Catastrophes

8/14/2019 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-

5

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

GeneralCologne Re6


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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,

7

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-

8

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)



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



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.


13/2013

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.



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.


15/20


16/20

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


17/20

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


18/20

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


19/20

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

Documents

Cosmic Catastrophes