A SEMINAR ON METEORITES : A SEMINAR ON METEORITES CONTENTS : CONTENTS INTRODUCTION
HISTORY OF METEORITES
CLASSIFICATION OF METEORITES
REFERENCE INTRODUCTION : INTRODUCTION A Meteorite is a natural object originating in outer space and the body that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites are derived from small astronomical objects called meteoroids Willamette Meteorite discovered in the U.S. state of Oregon in1907 Slide 4: Meteorites are pieces of asteroids that travel through our solar system and land on Earth.
Before they land they are termed meteors or shooting stars.
They are rocks from space! According to layman
They are the remains of the ancient solar nebula according to scientist. A piece of rock or metal that has fallen to the earth's surface from outer space as a meteor. Over 90 per cent of meteorites are of rock while the remainder consist wholly or partly of iron and nickel this is the definition from famous Oxford dictionaries. Contd, : Contd, In 1794 Ernst F. F. Chladni a German physicist and musician wrote a 60 page book titled On the Origin of the Pallas Iron and Others Similar to it, and on Some Associated Natural Phenomena in which he proposed that meteor-stones and iron masses enter the atmosphere from cosmic space and form fireballs as they plunge to Earth. This was a very controversial statement at the time, since meteorites were thought to be of volcanic origin. With this book Chladni also became one of the founders of modern meteorite research.
After ten years his theory was validated and he is termed as the “father of meteoritics” Ernst F. F. Chladni HISTORY OF METEORITES : HISTORY OF METEORITES Throughout the ages, meteorites were venerated as sacred objects by different cultures and ancient civilizations. The spectacular fall of a meteorite, accompanied by light and sound phenomena, such as falling stars, smoke, thunder, and sonic booms, has always kindled the human imagination, evoking fear and awe in everyone who witnesses such an event. For obvious reasons, the remnants of these incidents, the actual meteorites, were often kept as sacred stones or objects of power. They were worshiped, and used in their respective religious ceremonies. Slide 7: From Prehistoric Times to Ancient Egypt
Actually, several Native American tribes venerated pieces and fragments of the Canyon Diablo meteorite, a giant iron meteorite that was excavated Arizona's famous Meteor Crater upon its impact about 50,000 years ago.
from the iron found in them many knives and daggers have been recovered from the tombs of Egyptian Pharaohs, from Mesopotamian sanctuaries, and from the graves of the leaders of the Aztecs, Maya, and Inca, in both Americas. From Ancient Greece to Mecca
The ancient civilizations of the occident are no exception, and there are several examples of the worship of meteorites in Greco-Roman tradition. The Palladion of Troy, the Artemis of Ephesos, as well as the Cone of Elagabalus in Emesa, were actually meteorites - stones that had fallen from the sky, objects from heaven, believed to contain supernatural powers.
There is another famous example from the Middle East, but there is some dispute about whether the object of veneration is actually a meteorite or not. We are referring to the "Hadschar al Aswad", the sacred "black stone", of Mecca and Medina. Slide 8: METEOR SHOWERS Slide 9: A meteorite shower captured by a Russian TV Crew CLASSIFICATION OF METEORITES : CLASSIFICATION OF METEORITES Aerolites or stones : Aerolites or stones Chondrites: they are so named because of presence of chondrulus or chondri. When the meteoroids are small rounded bodies consist of olivine and pyroxene.
Carbonaceous Chondrites: it is an unique among meteorites which consist largely of hydrated iron-magnesium silicate ( serpentine or chlorite like mineral) and containing up to 10% complex organic compound.
Achondrites: Achondrites are a diverse group of stony meteorites do not contain chondrulus and are more coarsely than the chondrites. Many achondrites resemble terrestrial igneous rock composition and texture hence has probably crystallized from silicate metal. SIDEROLITES or STONY IRON : SIDEROLITES or STONY IRON Siderolites or stony iron meteorites are made up of nickel, iron & silicate in approximately equal amounts. Siderolites are further divided as
Pallasite: they are made up of nickel iron enclosing grains of olivine, which often show good crystal forms. It is first of the preserved meteorite in our country.
Mesosiderites: Mesosiderites take their name from the Greek words for “iron” and “half” and are comprised of approximately equal amounts of nickel-iron and stony components. Most are brecciated and many show broken and irregular inclusions of silicate minerals, rich in magnesium. Silvery metallic flakes and veins stand out starkly against the dark silicates SIDERITE or IRON : SIDERITE or IRON The silicates or iron meteorites consist of one or two nickel iron metallic phases, generally with accessory troilite(FeS), schreibasite (Fe,Ni)3P and graphite.
Additional accessory such as cohenite (Fe3C), daubreelite( FeCr2S4) and chromite occur more rarely. These accessory minerals are present as small rounded or lamellar grains scattered through the metal. The metal generally showed a definite structure known as widmanstatten figure.
Which are brought out by etching a polished surface with an alcoholic solution of the nitric acid. This structure consists of the lamellae of kamacite(α-(Fe,Ni); Fe0+0.9Ni0.1 )bordered by taenite(γ-(Ni,Fe)). WIDMANSTÄTTEN PATTERNS : WIDMANSTÄTTEN PATTERNS The iron-nickel core is the last part of a differentiated planetary body to cool because it is insulated by the outer layers of rock.
The weight of the outer layers squeezes the iron core as it cools. The combination of slow cooling and constant compression produces a criss-cross pattern of crystals that is preserved when the iron core ﬁnally solidiﬁes. When the cut face of an iron meteorite is etched with acid, the pattern becomes visible.
This pattern observed in etched iron meteorites is called a Widmanstätten pattern.. Frequency of Meteorites : Frequency of Meteorites Frequency is termed as number of Fall and Find. A fall is defined as the meteorite that was seen falling and subsequently collected. A find is defined as the meteorite which was not seen falling but found later during investigation for mineral deposits and recognized through its structure, mineralogy and chemistry. ORIGIN OF METEORITES : ORIGIN OF METEORITES Urey suggests, that chondrites may be plantesimals which failed to accumulate into a planets.
Farrington as a result of year’s of study summed up as; meteorites are portions of a distrupted mass of cosmic matter, which had a spherical form, increased in density towards the center, and cooled from a liquid or a semi liquid to a solid state before distruption. Contd… : Contd… Daly (1943) using all the evidence available came to conclusion that the ancestral body of cosmic matter that give rise by disruption to the meteorites.
The origin from a disrupted planet implies that the disruption probably took place in the early in the evolution.
As fragments of tidally disrupted atmosphere less bodies such as asteroids and satellites and as accretion of gas or fine particles of matter in the open space in the universe
The average age of them is 7X109 years by U235 - Pb206 IMPORTANCE : IMPORTANCE 24 km wide crater created by impact of meteorite called “Ries” crater in southern Germany has produced micro to nano level diamond.
They also contain gem minerals, such as peridot.
Hydro carbons in meteorite resemble “ in many aspect the hydrocarbons in the products of living things and sediments on Earth”.
Carbonaceous meteorites may provide the clue for understanding the origin of the solar system and also the origin of life. Conclusion : Conclusion They are rocks from space!
They are the remains of the ancient solar nebula.
Throughout the ages, meteorites were venerated as sacred objects by different cultures and ancient civilizations.
Carbonaceous meteorites may provide the clue for understanding the origin of the solar system and also the origin of life and may have significantly contributed to the earth’s initial endowment of organic matter.
Carbonaceous meteorite are believed to be relatively un altered condensates from the early solar nebula, thus they contain a unique record of chemistry that took place about 4600 m.y. ago. REFERNCE : REFERNCE Brian Mason, Principles of GEO CHEMISTRY, Edition 1958, pp 9-21.
Arthur H. Brownlow, GEO CHEMISTRY, Edition 1979, pp 14- 25.
RichardnBerendzen, Richard Hart, Daniel Seeley, MAN DISCOVERS THE GALAXIES, Edition 1976, pp 11-25.
C.S.Pichamuthu, ARCHEAN GEOLOGY, Edition 1985, pp 62-64.
Identification of diamino acids in the Murchison meteorite by Uwe J. Meierhenrich Guillermo M. Muñoz Caro Jan Hendrik Bredehöft Elmar K. Jessberge r and Wolfram H.-P. Thiemann Slide 22: Thank you