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 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 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 H chondrite group L chondrite group LL chondrite group Enstatite chondrite class CBa chondrite subgroup CBb chondrite subgroup Ordinary chondrite class CV oxA chondrite oxidized Allende like subgroup CV oxB chondrite oxidized Bali like subgroup CV red chondrite reduced subgroup 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 5 members Chondrites Stony meteorites most common meteorites and represent the oldest solids that are the building blocks of the solar system Parent bodies were small medium asteroids not planetoids Contain up to 80 chondrules which were freely floating molten drops in space Few m to 1 cm spheres Mostly olivine and pyroxene also feldspathic glass or crystals with minor troilite FeS chromite phosphates 15 groups of chondrites Chondrite groups Ordinary make up 80 of the meteorites and 90 of chondritic meteorites abundant chondrules variable Fe Ni lead to H L and LL chondrites Carbonaceous 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 specimen Enstatite Chondrites 2 of chondritic meteorites very chemically reduced enstatite rich chondrules and abundant metal and sulfide minerals Peekskill Meteorite Peekskill 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 meteorite Car 10K Meteorite 75K Achondrites Stony 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 body 2 3 of these meteorites are HED type originating from one asteroid Vesta 4 there is a large impact crater observed on this asteroid Also includes Martian and lunar meteorites The Johnstown Diogenite Lunar Meteorite Allan Hills 81005 Martian Meteorites All are igneous lherzolitic to basaltic composition and some contain hydrated carbonates and sulfates evidence of liquid water ALH84001 is 4 5 ga contains carbonate veins 3 6 4 ga Organic matter PAH aligned magnetite crystals proposed nanofossils careful very controversial ALH84001 ALH84001 round carbonate grains Nahkla Meteorite Iron Meteorites 5 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 Ni Taenite Fe Ni alloy at 80 20 to 45 65 Fe Ni Widmanst tten pattern finely interweaved Kamacite and Taenite Octahedrites Classified on Ni content Ataxites Octahedrites Hexahedrites Stony iron Meteorites Mix of iron nickel alloy and silicate minerals mostly olivine 1 of meteorites Pallasites are thought to form a the coremantle boundary of differentiated asteroids Mesosiderite equal parts metal alloy and silicate with a breccia texture Identifying a meteorite Fusion crust dull black to dark brown often soft can be weathered to red but can flake off Density generally dense Chondrules are specifically meteoritic Never porous but can be dimpled with surface depressions 99 of meteorites are magnetic Unusually high Ni content Fusion crust forms on entry through the atmosphere Meteorite Comet Impacts P T space Chicxulub Yucatan Peninsula Mexico K T event at 64 98 ma formed from a 6 12 mile diameter asteroid impact 50 megaton blast Barringer Meteor Crater Arizona formed from Canyo Impact Craters Many 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 Megatsunamis Meteorite impact in the ocean displaces huge quantities of water instantly The Chixculub crater impact generated a megatsunami 150 300 feet high Energy of an impact Kinetic 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 impact Shatter cone Materials indicating Meteorite Impacts Tektites Glass formed from impact Diaplectic Glass Glass formed through fusion of different minerals not melted but fused What Happens to minerals that are there but not melted Shock Quartz Lamellae retaining evidence of impact Diamonds Very small diamonds can form from impacts and are found in meteorite impact craters around the world Diamonds can also form in meteoritesthese can be gray to black Lonsdalite Hexagonal allotrope of diamond specific to meteorite impacts thought to form from graphite in meteorites Quartz Polymorphs Coesite and Stishovite found associated with impact craters