Presentation on theme: "Meteorites Antarctica Tagish Lake, B.C. Thin Section Martian Stone Willamette Iron."— Presentation transcript:
Meteorites Antarctica Tagish Lake, B.C. Thin Section Martian Stone Willamette Iron
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
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. Ernst Florens Friedrich Chladni Chladni (Father of Meteoritics)
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
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. L'Aigle Map of the L'Aigle Strewnfield
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. Meteorite Classification
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). 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. Chondrites
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.
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 50°C.
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. Ordinary Chondrites SOUSLOVO Meteorite type: L4 Specimen weight: 11.91 kilos Dimensions (mm): 190 x 231 x 158
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.
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.
NORTON COUNTY Meteorite type: AUB Specimen weight: 111.20 g Dimensions (mm): 65 x 47 x 34 Estimate: $2,400 - $3,000
1 ton (~908,000 grams) One of the largest stony meteorites $25/gram = $22.7 million Norton County On display at Institute of Meteoritics at UNM
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
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. Iron Meteorites
MeteoriteCountryFoundStructural ClassGroupWeight kg HobaNamibia1920AtaxiteIVB60,000 Campo del CieloArgentina1990OctahedriteIAB37,000 Cape York (Ahnighito)Greenland1894OctahedriteIIIAB31,000 ArmantyChina1898OctahedriteIIIE23,500 BacubiritoMexico1863OctahedriteUNG22,000 Cape York (Agpalilik)Greenland1963OctahedriteIIIAB20,000 MbosiTanzania1930OctahedriteUNG16,000 Campo del CieloArgentina1576OctahedriteIAB15,000 WillametteUSA1902OctahedriteIIIAB14,900 ChupaderosMexico1854OctahedriteIIIAB14,100 MundrabillaAustralia1911OctahedriteIIICD12,000 MoritoMexico1600OctahedriteIIIAB11,000 Largest Iron Meteorites
MeteoriteCountryFoundClassWeight kg HuckittaAustralia1937Pallasite1,400 KrasnojarskRussia1749Pallasite700 BrenhamUSA1947Pallasite450 MeteoriteCountryFellClassGroupWeight kg JilinChina1976ChondriteH51,770 Norton CountyUSA1948AchondriteAubrite1,073 Long IslandUSA1891ChondriteL6(broken) 564 ParagouldUSA1930ChondriteLL5371 BjurboleFinland1899ChondriteL/LL4(broken) 330 Largest Stony-Iron Meteorites Largest Stony 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. Stony-Iron Meteorites
Pallasite GLORIETA Meteorite type: PAL-UNGR Specimen weight: 464.3 g Dimensions (mm): 219 x 169 x 3
ESTHERVILLE Meteorite type: MES-A3/4 Specimen weight: 59.80 grams Dimensions (mm): 49 x 74 x 5 Mesosiderite
“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.
Strewnfield map of Dar al Gani, Libya 853 meteorites plotted
Tagish Lake Carbonaceous Chondrite 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 26.
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 ~S30°E. Tagish Lake