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Meteorite presentation outline
Feb 26, 2008
Tom Scharff
I. Introduction
A. Disclaimer - this is not a scientific paper, and I am not going to credit each source. I have not done any original research, and I have put this presentation together using a variety of sources.
B. Background - I have been collecting meteorites since the late 1990's, I have never found a specimen, but have amassed my collection through purchases and the occasional gift.
II. Definitions of terms (see handout)
III. Naming of Meteorites - Usually named for the nearest town or geographic feature to the location where they are found.
IV. Types of Meteorites
A. Stony
1. Chondrite- contain chondrules (80-86% of falls)
a. High Iron
b. Low Iron
c. Very Low metal
2. Achondrite- do not contain chondrules (7-8% of falls)
B. Stony/Iron- iron-nickel and stony materials in roughly equal proportions (1-2% of falls)
1. Pallasite - nickel-iron with olivine crystals
2. Mesosiderite - partly stone, partly nickel iron, in a melded mixture
C. Nickel-Iron (4-6% of falls, ~66% of finds))
D. Tektite - dry, glassy "splash material" which may have originated from Earth or the Moon, but which traveled through space, and can be considered meteoritic
1. Indochinite - possible impact crater under Antartic ice sheet
2. Moldavite - 14.8mya, same age as Nordlinger Ries crater, GER
3. Ivory Coast - 1mya, same age as Lake Bosumtwi Crater
4. Americanites - 34mya, same age as Chesapeake Bay impact crater
E. Anomalous - Some meteorites cross categories, like the silicated iron meteorites
V. Meteorites and Wrongs - how to tell them apart
A. Usual positive criteria of meteorites
1. Thin dark-colored crust of a different color than interior, shows evidence of melting
2. Irregular, nonspherical shape
3. Heavy weight
4. Different appearance from other nearby rocks
5. Attracted to magnets
B. Usual negative criteria (properties of meteorwrongs)
1. Holes or vesicles (slag often contains voids, giving a spongy appearance)
2. Easily breakable (concretions break fairly easily, nickel-iron meteorites are very hard)
3. Spherical shape
VI. Collecting and preserving meteorites
A. Finding meteorites - good luck!
1. Chasing them
B. Buying meteorites
1. Reputable dealers
2. eBay - Buyer Beware
C. Preserving meteorite specimens in a collection
1. Labels - keep them labeled!
2. Dry conditions - helps prevent rusting
3. Cleaning (if necessary)
a. Dusting - gently!
b. Removing rust - soak in alcohol or oxalic or tartaric acid, sodium citrate, or sodium hydro-sulfate
c. lacquer - do NOT lacquer scientifically important specimens
D. What to collect?
1. Whole individuals - intact specimens will probably have some fusion crust, expressed in percent
2. Slices - Complete and part slices, if the perimeter is the exterior of the meteorite, the slice is complete. Some thin sections are translucent or transparent, particularly pallasites!
3. Fragments - not usually polished, fragments of chondrites will often show chondrules
4. End pieces - like the heel of a loaf of bread, these have one sawn surface (usually polished), and the rest is the exterior of the individual
5. Micro-mounts - often kept in small vials, or gelatin capsules
VII. History, trivia, and some places to see and learn about meteorites
1. Books
A. Farrington's Catalog - 1909 (Curator of Field Museum)
B. Nininger's Find A Falling Star - 1972
C. Norton's Rocks From Space
2. Museums
A. Smithsonian Institution - Washington DC mineralsciences.si.edu
B. Hayden Planetarium - NYC haydenplanetarium.org
C. UNM Institute of Meteoritics - Albuquerque epswww.unm.edu/iom
D. American Museum of Natural History - NYC amnh.org
D. UW Geology Museum - upstairs! geology.wisc.edu/~museum
F. Natural History Museum -London internt.nhm.ac.uk
3. Internet
A. Universities
a. UNM - epswww.unm.edu/meteoritemuseum
b. Washington University - Dr. Randy L. Korotev - meteorites.wustl.edu/more_info_nonlunar.htm (Korotev is a UW graduate!)
c. ASU - largest university-based collection meteorites.asu.edu
B. Government
a. Meteoritical Society - tin.er.usgs.gov/meteor
b. Antarctic Search for Meteorites program (ANSMET) geology.cwru.edu/~ansmet
c. NASA - www2.jpl.nasa.gov/snc
C. Other educational sites
a. Wikipedia (don't laugh!) en.wikipedia.org/wiki/Meteorite
b. Meteorite Times Magazine meteorite-times.com
c. Science Magazine sciencemag.org
d. International Meteor Organization imo.net
e. Meteorites Australia meteorites.com.au
f. American Meteor Society amsmeteors.org
g. International Meteorite Collector's Association imca.cc
D. Dealers
a. Michael Blood Meteorites - michaelbloodmeteorites.com
b. Allan Langheinrich - nyrockman.com
c. Michael Casper - caspermeteorites.com
d. Robert Haag - meteoriteman.com
e. Blaine Reed - reedmeteorites.com
f. New England Meteoritical Services meteorlab.com
g. Daryl Pitt - macovich.com
h. Ken Regelman - meteorites4sale.net
VIII. Examples
1. Scharff collection
2. Large TKW
A. Canyon Diablo, AZ TKW >30 tons
B. Sikhote-Alin Siberia >70 tons TKW, largest piece 1745 kg
C. Hoba, Namibia found 1920, 60,000 kg (largest known)
D. Willamette, Oregon found 1902 but known previously to natives, 15.5 ton oriented iron is the largest found in USA
E. Cape York, Greenland - 31 ton Ahnighito, 15 ton Agpalilik and others
F. Gibeon, Namibia estimated TKW > 50 tons
G. Brenham, Kansas - largest oriented Pallasite
3. Known parent bodies
A. Moon
B. Mars and its moons
C. Asteroids
D. Comets
4. Historic falls
A. Ensisheim, Alsace November 7, 1492 a 127KG stone landed in a wheat field
B. Sikhote-Alin Siberia Feburary 12, 1947
C. Tunguska, Siberia June 30, 1908 - no fragments have been reported
D. Paragould, Arkansas February 17, 1930 Third largest meteorite found in USA, found by HH Nininger
5. Hammers
A. Peekskill, NY - October 9, 1992 Hit a parked 1980 Chevy Malibu
B. Sylacauga, AL - November 30, 1954 Hit Mrs Hodges in the abdomen
C. Claxton, GA - December 10, 1984 Struck a mailbox
D. Park Forest, IL - March 26, 2003 Several stones struck houses and other objects
E. Nakhla, Egypt - June 28, 1911 reportedly killed a dog (contains small tunnels which may have been cause by bacteria)
6. Scientific interest
A. Murchison - Fell September 28, 1969 Victoria, Australia - Amino acids not found on Earth
B. ALH 84001 - Igneous Martian rock with microscopic fossils
C. Orgueil, France - May 14, 1864 first confirmed organic materials in a meteorite
D. Cold Bokkeveld, South Africa - October 13, 1838 contains microscopic diamonds with Xenon gas
7. Wisconsin meteorites in UW geology museum
A. Colby, Clark Co. - Fell July 4, 1917 L6 (S3; veined) chondrite. Two stones (one weighing ~75lbs, total weight ~200lbs) fell 1917, July 4th, 18:20 hrs after the appearance of a luminous meteor with a trail of black smoke, moving from NW. to SE., and loud explosions were heard, The larger of the two fell in a pasture, and was embedded about five feet into the ground. This meteorite was very cold and frost formed on it after it was dug out of the ground. The combined weight of the meteorites was more than 200 pounds
B. Kilbourn, Columbia Co. - Fell Jun 16, 1911, struck a building 772 grams(H5)
C. Belmont, Lafayette Co. - Found spring 1958,One mass of 25.3kg Olivine-bronzite chondrite (H6), veined.
D. Trenton - Found 1858, 33 lbs (IIIAB)
E. Algoma, Kewaunee Co- plowed up 1887 9LB Med Octahedrite IIIA
8. Wisconsin meteorites NOT in UW geology museum
A. Vernon County, Fell March 26,1865 - Olivine-bronzite chondrite (H6), veined
B. Pine River (Saxeville, Waushara Co.) found ~1894 3.6kg, med octahedrite w/ silica inclusions
C. Mt Morris, Waushara Co. found 1937 but known previously, 3 fragments TKW 676g (achondrite Winonaite)
E. Angelica, Shawano Co., found 1916, Med Octahedrite IIIA 14.8kg mass plowed up
F. Hammond, St. Croix Co. found 1884 53 LB mass plowed up, Medium octahedrite
G. Oshkosh, Winnebago Co found 1961, about a dozen small fragments, the largest about 2" in diamete, TKW 144g (H Chondrite)
H. Zenda, Walworth Co found 1955, medium octahedrite 3.7kg mass plowed up
I. Rock Elm (450MYA) 67,500 MPH, 650-700 foot meteorite, ~1000 Megatons "lifted the earth at its center more than 1,650 feet and sent shock waves through the rocks, crushing them" (no meteorites found!)
9. Aesthetic beauty
A. Sikhote-Alin - thumbprinted iron
B. Millbillillie
C. Gibeon
D. Pallasites
E. Tektites - Lighter color indicates higher silica content
IX. Top 10 anticipated questions
1. Where do you get them? Have you ever found one? I purchased the pieces in my collection from dealers and rock shops. I have never found one.
2. How fast are they travelling when they hit the atmosphere? 10-70km/sec (approx 20,000-150,000 MPH) (objects faster than 160,000 MPH tend to leave the solar system) An object moving around 11,000 MPH at 87 miles of altitude will be accelerated to almost 40,000 MPH by the Earth's gravitational pull as it falls to about 60 miles high. From there, it begins to glow from friction as it decelerates. From 60 down to 40 miles high, it loses about 70% of its velocity, as it does this, it loses mass due to crumbling. From 40 down to 20 miles it forms a glassy fusion crust on its outside. It loses 3-6mm per second off its surface, due to this friction. Once it gets within about 20 miles of the surface, it has lost enough speed that it no longer glows.
3. How fast when they land? Small ones slow to just a few hundred KM/hr, large ones (over a few hundred tons) don't slow down much at all!
4. Why are they important?
A. Extraterrestrial samples with no space mission required -samples of the moon (especially parts where none of the lunar missions landed), mars, asteroids
B. Amino acids and fossils found in meteorites may demonstrate that life on earth could have been seeded from space
C. Allow for study of conditions during formation of solar system
D. Early source of iron for ancient peoples
5. Are they hot or cold when they land? Despite the heating from the friction of Earth's atmosphere, the cold core temperature from space (around -150F) causes them to "frost" once they land.
6. How can we determine the parent body? Falls observed from multiple angles can have their paths computed. If this can be done with enough accuracy, the parent body can be located. Other methods include comparing chemical composition of the meteorite with the composition of other objects in the solar system.
7. How big are most meteorites when they enter the atmosphere? When they land? They lose about 90% of their mass by falling through the atmosphere.
8. How much are they worth? Depends on a number of factors, including total known weight, and how much of the mass is in private hands. In some countries, such as Australia, they are not allowed to be sold. In USA they are property of the landowner. Irons are usually the least expensive, although some of them are not very stable and will tend to rust away. Ordinary chondrites are fairly common, and will generally be affordable, carbonaceous chondrites tend to be scarcer. Due to their beauty, pallasites are sought after by collectors and command fairly high prices. The rarest stony meteorites are the achondrites, the SNC meteorites are from mars- those and the lunar meteorites command the highest prices.
9. How many have been discovered? I think there have been thousands of different finds. How many have been observed to fall? Probably at least many hundred
10. What's the difference between lunar meteorites and the rocks the astronauts brought back? Lunar samples from NASA missions did not go through the atmospheric heating process, or the violent fragmentation from rapid deceleration, so those moon rocks (as modeled in the UW Geology Museum) lack many properties of meteorites.
11. Is a satellite a meteorite if a piece of it lands? ????? Good question!