meteorite composition

Click here to load reader

Post on 06-Jan-2016

29 views

Category:

Documents

0 download

Embed Size (px)

DESCRIPTION

Meteorite composition. Major groupings: Stony meteorites Chondrites Achondrites Iron meteorites Octahedrites, hexahedrites, ataxites Stony-iron meteorites Pallasites Mesosiderites. Chondrites Carbonaceous chondrite class CI chondrite (Ivuna-like) group - PowerPoint PPT Presentation

TRANSCRIPT

  • Meteorite compositionMajor groupings:Stony meteoritesChondritesAchondritesIron meteoritesOctahedrites, hexahedrites, ataxitesStony-iron meteoritesPallasitesMesosiderites

  • Chondrites Carbonaceous chondrite class CI chondrite (Ivuna-like) group CM-CO chondrite (mini-chondrule) clan CM chondrite (Mighei-like) group CO chondrite (Ornans-like) group CV-CK chondrite clan CV chondrite (Vigarano-like) group CV-oxA chondrite (oxidized, Allende-like) subgroup CV-oxB chondrite (oxidized, Bali-like) subgroup CV-red chondrite (reduced) subgroup CK chondrite (Karoonda-like) group CR chondrite clan CR chondrite (Renazzo-like) group CH chondrite (Allan Hills 85085-like) group CB chondrite (Bencubbin-like) group CBa chondrite subgroup CBb chondrite subgroup Ordinary chondrite class H chondrite group L chondrite group LL chondrite group Enstatite chondrite class EH chondrite group EL chondrite group Other chondrite groups, not in one of the major classes R chondrite (Rumuruti-like) group K chondrite (Kakangari-like) grouplet (a grouplet is a provisional group with
  • ChondritesStony meteorites most common meteorites and represent the oldest solids that are the building blocks of the solar systemParent bodies were small-medium asteroids, not planetoids!Contain up to 80% chondrules, which were freely floating molten drops in spaceFew mm to 1 cm spheresMostly olivine and pyroxene, also feldspathic glass or crystals with minor troilite (FeS), chromite, phosphates 15 groups of chondrites

  • Chondrite groupsOrdinary make up 80% of the meteorites and 90% of chondritic meteorites, abundant chondrules, variable Fe-Ni lead to H, L, and LL chondritesCarbonaceous chondrites less the 5% of chondritic meteorites, few chondrules, more lithophile elements (Ca, Mg, K, Cr, Al, Cl,), high levels of water and organic compounds - many types based on characteristic specimenEnstatite Chondrites 2% of chondritic meteorites, very chemically reduced enstatite-rich chondrules and abundant metal and sulfide minerals

  • Peekskill MeteoritePeekskill Meteor: October 9, 1992. This famous fireball was seen and filmed across several eastern states. It broke up into many fragments, one of which hit the trunk of Michelle Knapp's 1980 Chevy Malibu. When Ms. Knapp investigated a crash sound outside her Peekskill, NY home, she discovered the damaged trunk and found a warm 12-kg meteorite lying beside the car. 12-kg Ordinary Chondritic meteoriteCar $10KMeteorite $75K

  • AchondritesStony meteorite similar to terrestrial basalts or plutonic rocks, represent 8% of meteorites grouped on the basis of Fe/Mn and 17O/18O ratios characteristic of the parent body2/3 of these meteorites are HED type, originating from one asteroid, Vesta 4 - there is a large impact crater observed on this asteroidAlso includes Martian and lunar meteoritesLunar Meteorite Allan Hills 81005 The Johnstown Diogenite.

  • Martian MeteoritesAll are igneous, lherzolitic to basaltic composition, and some contain hydrated carbonates and sulfates, evidence of liquid waterALH84001 is 4.5 ga, contains carbonate veins 3.6 4 ga, Organic matter (PAH), aligned magnetite crystals, proposed nanofossils (careful!!) very controversialALH84001Nahkla MeteoriteALH84001 round carbonate grains

  • Iron Meteorites5% of meteorites, but 90% of the mass of recovered meteorites and all of the largest meteorites (66 tons is the record) - primarily composed of iron-nickel alloy intergrowths:Kamacite Fe-Ni alloy at 90:10 to 95:5 Fe:NiTaenite Fe-Ni alloy at 80:20 to 45:65 Fe:NiWidmansttten pattern finely interweaved Kamacite and Taenite (Octahedrites)Classified on Ni content: Ataxites>Octahedrites>Hexahedrites

  • Stony-iron MeteoritesMix of iron-nickel alloy and silicate minerals (mostly olivine), 1% of meteoritesPallasites are thought to form a the core-mantle boundary of differentiated asteroidsMesosiderite equal parts metal alloy and silicate with a breccia texture

  • Identifying a meteoriteFusion crust dull black to dark brown, often soft, can be weathered to red (but can flake off)Density generally denseChondrules are specifically meteoriticNever porous, but can be dimpled with surface depressions99% of meteorites are magneticUnusually high Ni content

  • Fusion crust forms on entry through the atmosphere

  • Meteorite/ Comet ImpactsP/T space??

  • Chicxulub, Yucatan Peninsula, MexicoK/T event at 64.98 ma, formed from a 6-12 mile diameter asteroid impact (50 megaton blast)

  • Barringer Meteor Crater, Arizona, formed from Canyon Diable Meteorite

  • Impact CratersMany famous impact craters, hundreds known on earth (why might there have been plenty more??)Sudbury, Ontario (250km diameter, 1.85 ga)Chesapeake Bay (90km diameter, 35 ma)Manson, Iowa (35km, 74ma)Barringer, Arizona (1.2km, 49 ka)Serpent Mound, Ohio (8km, 320 ma)Clearwater lakes, Quebec 36+26km diameter, 290 ma

  • MegatsunamisMeteorite impact in the ocean displaces huge quantities of water instantlyThe Chixculub crater impact generated a megatsunami 150-300 feet high

  • Energy of an impactKinetic energy going from very fast to stopping is a BIG change in energy

    What happens to that energy??

    Impactite any mineral formed as a result of this impactShatter cone

  • Materials indicating Meteorite ImpactsTektitesGlass formed from impact

  • Diaplectic GlassGlass formed through fusion of different minerals not melted, but fused

  • What Happens to minerals that are there but not melted?Shock QuartzLamellae retaining evidence of impact

  • DiamondsVery small diamonds can form from impacts and are found in meteorite impact craters around the worldDiamonds can also form in meteorites- these can be gray to black

    Lonsdalite - Hexagonal allotrope of diamond, specific to meteorite impacts, thought to form from graphite in meteorites

  • Quartz PolymorphsCoesite and Stishovite found associated with impact craters

    Warning the wikipedia description of this contains sections that are unreferenced and is incomplete in the story. While widely accepted, there are scientists with other theories for the K/T event and explanation for this feature

    The meteorite's estimated size was about 10 km (6 mi) in diameter, releasing an estimated 500 zettajoules (5.01023 joules) of energy, approximately 100 teratons of TNT,[1] on impact. By contrast, the most powerful explosive device ever detonated, the Tsar Bomba or Emperor Bomb, had a yield of only 50 megatons, which would make this impact 2,000,000 times more powerful than the Emperor Bomb.