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Meteorites
Martian Stone
Willamette Iron
Thin Section
Tagish Lake, B.C.
Antarctica
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Meteorites Historical
Meteorites were originally thought by many
cultures to have supernatural powers or that they
were gifts from the gods or heaven.
Winona found in cist at Elden Pueblo AZ
"Hadschar al Aswad", the sacred "black stone", in
the Kaaba, Mecca

Thunderstone of Ensisheim 1492
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In his booklet, "On the Origin of the Pallas Iron
and Other Similar to it, and on Some Associated
Natural Phenomena", published in 1794, he
compiled all available data on several meteorite
finds and falls. From this, he was forced to
conclude that meteorites were actually
responsible for the phenomena known as fireballs,
and, more importantly, that they must have their
origins in outer space. His view received
immediate resistance and mockery by the
scientific community. In the late 1790s, rocks
from space just didn't fit into the concept of
nature. However, nature itself came to Chladni's
aid in the form of two witnessed meteorite falls,
making him the father of a brand-new discipline -
the science of meteoritics.
Chladni (Father of Meteoritics)
Ernst Florens Friedrich Chladni
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Wold Cottage
On December 13, 1795, a stone of about 25kg was
seen to fall in Wold Cottage, England, by several
eyewitnesses. The fall occurred in broad
daylight, out of a clear, blue sky, refuting the
most popular explanations for the formation of
meteorites, such as lightning or condensation in
clouds. British chemist, Edward Howard, who
found it to contain grains of nickel-iron metal,
similar in composition to the iron meteorites
described in Chladni's book. Conservative
scientists kept on denying the obvious facts,
among them some of the most influential members
of the respected French Academy of Sciences.
The Wold Cottage Monument
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Map of the L'Aigle Strewnfield
L'Aigle
On April 26, 1803, a shower of about 3,000 stones
fell in broad daylight near L'Aigle, France,
witnessed by countless people. This incident
attracted much public attention, providing a
fertile ground for further research and the young
science of meteoritics. The French Minister of
the Interior commissioned the young physicist
Jean-Baptise Biot, a member of the French Academy
of Sciences, to investigate the fall, resulting
in a well-written paper that finally gave
meteoritics credibility.
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Meteorite Classification
Meteorite Classes Chondrites relatively
unaltered, formed as aggregates of primitive
solar system material, unmelted asteroids,
chondrules usually present, 86 of
falls. Achondrites processed by melting, formed
from magma, crust or mantle of asteroid, no
chondrules, 8 of falls. Iron meteorites
processed by melting, asteroidal core, 7 of
falls. Stony-iron meteorites processed by
melting, core-mantle boundary of asteroid, 1 of
falls.
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Meteorite Classification
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Meteorite Classification
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Meteorite Classification
Differentiated Meteorites
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Meteorite Classification
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Chondrites
Chondrites are more or less undifferentiated,
primordial matter that has remained nearly
unchanged for the last 4.5 billion years. These
stony meteorites formed nearly simultaneously
with the Sun. It is thought that small droplets
of olivine and pyroxene condensed and
crystallized from the hot primordial solar nebula
in form of small spheres that we nowadays call
chondrules. Chondrules accreted with other
material that condensed from the solar nebula
forming a matrix that constitutes chondrites and
chondritic parent bodies (asteroids).
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Chondrules
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Chondrites
In their chemical composition, chondrites
resemble the Sun, depleted of the most volatile
elements like hydrogen and helium. However, the
distribution of elements has not been uniform in
the original solar nebula - elemental composition
varied as did the conditions under which the
chondritic parent bodies formed. Different
asteroids formed in various regions of the
primordial solar nebula under different
conditions. Those parent bodies were further
subjected to different thermal and chemical
processes as well as to impacts with other
asteroids resulting in a variety of chondrites,
which have been categorized into several clans,
groups, and subgroups.
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Chondrite Petrologic Types
The chondrites of each clan and group are further
subdivided according to petrologic viewpoints and
are classified into petrologic types. Each type
is designated with a number from 1 to 7 whereas
type 3 builds the base line and describes a type
of chondrite that has suffered little or any
alteration by neither water nor any thermal
metamorphism. The petrologic types mirror the
degree of chemical equilibrium within the
minerals of a chondrite. Petrologic types 1 to 3
represent highly unequilibrated chondrites due to
a lack of thermal metamorphism while the types 4
to 7 are increasingly equilibrated due to
extended thermal processes.
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Carbonaceous Chondrites
Carbonaceous chondrites or C chondrites represent
some of the most pristine matter known, and their
chemical compositions match the chemistry of the
Sun more closely than any other class of
chondrites. Carbonaceous chondrites are
primitive and undifferentiated meteorites that
formed in oxygen-rich regions of the early solar
system so that most of the metal is not found in
its free form but as silicates, oxides, or
sulfides. Most of them contain water or minerals
that have been altered in the presence of water,
and some of them contain larger amounts of carbon
as well as organic compounds. The most primitive
carbonaceous chondrites have never been heated
above 50C.
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Orgueil (CI)
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Ordinary Chondrites
Chondrites of this clan are designated as
"ordinary" just because they are the most common
class of stony meteorites, representing more than
85 of all witnessed chondrite falls. The
mineralogies of ordinary chondrites are primarily
composed of olivine, orthopyroxene, and a certain
percentage of more or less oxidized nickel-iron.
Based on the differing content of metal and
differing mineralogical compositions the ordinary
chondrites have been subdivided into three
distinct groups that are designated as H, L, and
LL chondrites.
SOUSLOVO
Meteorite type L4Specimen weight 11.91 kilosDimensions (mm) 190 x 231 x 158
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Achondrites
The term "achondrite" was orginally used to
describe a stony meteorites without chondrules,
and this lack of chondrules was the primary
characteristic used to distinguish the two major
stony groups, achondrites and chondrites. However
some chondrites (very primitive or highly
equilibrated) lack chondrules. Achondrites can
be thought of as stony meteorites that have been
melted. Achondrites are samples of
differentiated planetary bodies, and therefore
represent a very heterogeneous class of
meteorites. Most of them are primitive that is,
nearly chondritic in composition with an age
similar to the primordial chondrites. These
so-called primitive achondrites are the residues
from partial melting that took place on small
parent bodies having chondritic compositions.
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Achondrites
More evolved achondrites, have experienced a more
extensive igneous processing including magmatic
processes similar to geological activities
encountered on Earth. Some of these achondrites
are basalts, plagioclase and pyroxene-rich
volcanic rocks that represent the upper crust of
their parent bodies. Others are olivine-rich
plutonic rocks that formed in deeper regions of
the crust and experienced prolonged thermal
processing.
Several groups of evolved achondrites can be
assigned to specific parent bodies. The
meteorites of the HED group are believed to be
samples of 4 Vesta, one of the largest asteroids
in our solar system. Other basaltic achondrites,
such as aubrites and angrites, are also
considered to have an asteroidal origin, although
their parent body is unknown.
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NORTON COUNTY
Meteorite type AUBSpecimen weight 111.20 gDimensions (mm) 65 x 47 x 34Estimate 2,400 - 3,000
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Norton County On display at Institute of
Meteoritics at UNM
1 ton (908,000 grams) One of the largest stony
meteorites 25/gram 22.7 million
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Achondrites
A few rare achondrites can be assigned to larger
parent bodies - the true planets and their
moons. The rare meteorites of the LUN group are
genuine pieces of our own Moon - a fact that has
been proven by comparisons to samples of Moon
rocks that were returned to Earth by the Apollo
missions during the late 60's and early 70's.
The equally rare achondrites of the SNC group
are believed to have their origin on the planet
Mars.
First Lunar Meteorite ALH 81005
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Iron Meteorites
Iron meteorites are characterized by the presence
of two nickel-iron alloy metals kamacite and
taenite. These, combined with minor amounts of
non-metallic phases and sulfide minerals, form
the three basic subdivisions of irons. Depending
upon the percentage of nickel to iron, these
subdivisions are classified as hexahedrites
(4-6 Ni) octahedrites (6-12 Ni) ataxites
(12 Ni) Octahedrites, which are the most
common type of iron meteorite, exhibit a unique
structural feature called the Widmanstätten
pattern when etched with a weak acid. This unique
crystal pattern is the result of the combination
of the two nickel-iron minerals kamacite and
taenite being present in approximately equal
amounts.
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Widmanstätten
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Ablation Surfaces on Iron Meteorites
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Largest Iron Meteorites
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Largest Stony-Iron Meteorites
Largest Stony Meteorites
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Stony-Iron Meteorites
Stony-irons consist of almost equal amounts of
nickel-iron alloy and silicate minerals. Although
all stony-irons may not be genetically related or
have similar composition, they are combined into
one group and divided into two subgroups for
convenient classification. The Pallasite group
is characterized by olivine crystals surrounded
by a nickel-iron structure which forms a
continuous enclosing network around the silicate
portion. Mesosiderites, on the other hand,
consist mainly of plagioclase and pyroxene
silicates in the form of heterogeneous aggregates
intermixed with the metal alloy. No distinct
separation between the metal and silicate phases
is readily apparent as it is with the Pallasites.
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Pallasite
GLORIETA
Meteorite type PAL-UNGRSpecimen weight 464.3 gDimensions (mm) 219 x 169 x 3
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Mesosiderite
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Fossil Meteorites
Oldest of these fossils is the meteorite of
Osterplana, Sweden, that was found in 1987
imbedded in some limestone. This limestone, which
dated from Ordovician times, revealed to the
scientists that the imbedded meteorite had fallen
480 million years ago! The meteorite of
Osterplana is even older than the Brunflo
meteorite which previously held the record for
the "oldest". Brunflo, which was also found in
Swedish limestone in 1980, has a terrestrial age
of 450 million years. These fossils do not
preserve most of the original meteoritic
mineralology, but are replaced by terrestrial
mineralization. The oldest intact meteorite is
the Lake Murray iron. A single mass was found in
a gully in Oklahoma in 1933. The meteorite was
imbedded in some Antler Sandstone dating from the
Lower Cretaceous, suggesting that Lake Murray
landed in a near-shore, shallow sea, while these
beds were being deposited about 110 million years
ago.

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Saharan Find
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Dar al Gani 749 Carbonaceous Chondrite (95kg)

Largest meteorite ever found in Libya
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Strewnfield map of Dar al Gani, Libya
853 meteorites plotted
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On January 18, 2000 A brilliant fireball followed
by loud detonations was widely observed over the
Yukon Territory and northern British Columbia. 
The fireball was also detected by satellites in
Earth orbit.  Dust clouds from terminal
fragmentation events were widely observed.
Pieces of a 56-metric-ton meteorite rained down
over a wide area of Canada. Many pieces landed on
the frozen Tagish Lake, allowing scientists to
recover numerous samples, and giving the
meteorite its name.   Mr. Jim Brook recovered
several dozen meteorites totaling 1 kg on the
ice of Taku Arm, Tagish Lake, on January 25 and
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Tagish Lake Carbonaceous Chondrite
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Tagish Lake
Between April 20 and May 8, 500 additional
specimens were located on the ice of Taku Arm and
a small, unnamed lake 1.5 km to the east.  Only
200 were retrieved however, as many had melted
down into the ice making their collection time
consuming recovery was prioritized based on
meteorite mass and degree of disaggregation.  The
total mass collected was between 5 and 10 kg. The
strewn field is at least 16 km by 3 km, oriented
S30E.
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TAGISH LAKE STREWN FIELD
Tagish Lake
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Peekskill NY (1992)
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Terrestrial Impact Craters
Wolfe Creek, Australia
Meteor Crater, AZ
1.186 kilometers (.737 miles) 49,000 years
0.875 kilometers (.544 miles) 300,000 years
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Terrestrial Impact Craters
Chicxulub, Yucatan MX
Manicouagan, Quebec
100 kilometers (62 miles) 212 million years
170 km 64.98 million years
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