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Meteorites: Rocks from space

Meteorites: Rocks from space. Leonid meteor shower, 1998 European Fireball Network image. Meteoroid Meteor (fireball) Meteorite. 1992 Peekskill fireball video clips. (How to turn a $300 car into one worth $10,000.). Results of ablation: fusion crust, thumbprints, fragmentation.

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Meteorites: Rocks from space

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  1. Meteorites: Rocks from space

  2. Leonid meteor shower, 1998 European Fireball Network image Meteoroid Meteor (fireball) Meteorite

  3. 1992 Peekskill fireball video clips (How to turn a $300 car into one worth $10,000.)

  4. Results of ablation: fusion crust, thumbprints, fragmentation

  5. Where do meteorites come from? Well-photographed meteors which have produced meteorites: Pribram, Czechoslovakia 1959 H5 Lost City, Oklahoma 1970 H5 Innisfree, Alberta 1977 LL5 Peekskill, New York 1992 H6 Tagish Lake, British Columbia 2000 CM1 Tagish Lake fireball

  6. Meteoroid orbits: aphelia between Mars & Jupiter (asteroid belt) Jupiter Mars

  7. Spectral reflectance of various meteorites & asteroids

  8. How do meteorites get to the Earth? (1)Perturbations by Jupiter can put asteroidal material into Earth-crossing orbits (Kirkwood gap clearing). (2)The Yarkovsky Effect can cause rotating m-sized objects to spiral inwards to (or outwards from) the sun. Cosmic-ray exposure (CRE) ages of meteorites (~1 Ma to ~0.5 Ga) give travel time needed for m-sized object-- consistent with Yarkovsky Effect

  9. Meteorites: different types Designation Proportion of metal & silicate Stony >> 50 % silicate Stony-iron ~ 50% metal, ~ 50% silicate) Iron >> 50% metal alloy

  10. Meteorite types & parent bodies # parent Designation Class & rock types bodies* Stony chondrites: agglomerate > 13 Stony achondrites: igneous, breccia > 8 Stony-iron pallasite: igneous > 3 Stony-iron mesosiderite: meta-breccia 1 (2) Iron many groups: igneous 50-80? * as inferred from chemical & isotopic studies

  11. Meteorites: different types Designation Type of rock Chondriteagglomerate-- never melted (stony) All elseigneous; impact breccias-- (stony, stony- melted at least once iron, iron)

  12. Chondrites All other rocks

  13. Undifferentiated meteorites: chondrites

  14. Chondrites • Meteorite type most often seen to fall (85.6%) • Earliest-formed rocks • (ages: ~4.55 b.y.) • Formed in solar nebula • Solar-like bulk composition (planetary building blocks)

  15. protoplanetary disks

  16. Chondrites have “solar composition” for most elements

  17. Chondrites • most contain chondrules • mm to sub-mm-sized objects • formed as melted dispersed objects • some contain refractory inclusions (CAIs) • mm to cm-sized objects • formed at high temperatures in solar nebula • some contain pre-solar grains • grains formed around other stars • some contain pre-biotic organic matter

  18. matrix chondrules 0.2 mm “Chondritic texture”: an agglomeration of chondrules and fine-grained matrix

  19. CAIs contains CAIs and pre-solar grains

  20. CAIs chondrules Carbonaceous chondrite Image: J.A. Wood

  21. Contains pre-biotic organic material

  22. Carbonaceous vs. Ordinary Chondrites

  23. Shocked chondrite: the 1992 Peekskill Fireball meteorite

  24. Gibeon (IVA iron) Millbillillie (eucrite) Differentiated meteorites DAG 485 (urelilite)

  25. Achondrite - any stony meteorite NOT a chondrite - samples of crusts and mantles of differentiated asteroids, the Moon, and Mars

  26. Irons - samples of the cores of differentiated asteroids Big! iron meteorite

  27. Iron meteorite: slow-cooling in a metallic core

  28. Mesosiderite origin: collision of a stripped metal core & another differentiated asteroid?

  29. Studies of meteorites provide evidence for: 1) widespread transient, high-T heating events in the solar nebula -- to form chondrules, CAIs 2) gas-dust chemical equilibrium in the solar nebula -- “equilibrium condensation model” valid 3) incomplete mixing & heating of dust in the solar nebula -- pre-solar material survived solar system formation!

  30. Studies of meteorites provide evidence for: 4) short-lived heat sources in meteorite parent bodies -- many asteroids melted & differentiated -- many asteroids metamorphosed & aqueously altered -- short-lived radionuclides, induction heating (?) were important in early solar system 5) water in many meteorite parent bodies -- in the form of ice or hydrated materials -- water in some asteroids too

  31. Studies of meteorites provide evidence for: 6) pre-biotic organic synthesis -- precursor materials for life formed in space! 7) impact & collision processes -- collisions important, probably even early in solar system -- asteroids may have been disrupted & reassembled

  32. Studies of meteorites provide evidence for: 8) interplanetary rock-swapping -- we have martian & lunar meteorites -- this has implications for life

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