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GEOL3045: Planetary Geology

GEOL3045: Planetary Geology. Lysa Chizmadia 16 Jan 2007 The Origin of Our Solar System. Interstellar Cloud Collapse. Initially, Interstellar Cloud of gas and/or dust Interstellar cloud of gas and dust disturbed and collapsed under its own gravity

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GEOL3045: Planetary Geology

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  1. GEOL3045: Planetary Geology Lysa Chizmadia 16 Jan 2007 The Origin of Our Solar System

  2. Interstellar Cloud Collapse • Initially, Interstellar Cloud of gas and/or dust • Interstellar cloud of gas and dust disturbed and collapsed under its own gravity • Probably due to shock waves from near-by supernova • As collapses, cloud heats up, starts to rotate and compresses in center • T  enough to vaporize dust • Takes ~ 100,000 years (100 ka) Images from: http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html

  3. Protostar & Accretion Disk • Due to rotation, nebula flattens into disk • Center compresses into protostar & rest of gas rotates around it • Gas flows into protostar, protostar grows into star • Centrifugal forces keep some gas from falling in • Accretion disk Orion Nebula Images from: http://en.wikipedia.org/wiki/Solar_System and http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html

  4. Thermodynamic Condensation • Gas starts to cool, eventually condenses into solids • First solids = most refractory ( T) • E.g. Ca, Al, Ti oxides with some silicates • I.e. CAIs (Ca, Al-rich inclusions) • Thermodynamic condensation • With T, less refractory elements condense • Mg > Si > Cr > Mn > Na > K > Fe > Ni > S Image from: Davis and Richter (2007) Treatise of Geochemistry vol. 1, chpt 15, p410

  5. Ca, Al-rich Inclusions • Ca, Al, Ti, Si, Mg • Oxides & Silicates • T >1300 K • Pb-Pb dating • 4.559 + 0.004 Ga • Confirmed by Rb-Sr & Sm-Nd dating • 26Al excess • > 2 Ma older than all other materials Images from personal archive

  6. Dust Balls • Solids start to accrete together into dust balls Image from: http://www.psi.edu/hartmann/pic-cat/pages/100_Solar_System_Origin.html

  7. olv fgr Chondrule Formation • Transient heating events form chondrules & igneous CAIs Images from: Jones (1990) Geochemica et Cosmochimica Acta v54 p1785 and http://www.psrd.hawaii.edu/Mar00/flashHeating.html

  8. Run-Away Growth • Solids continue to accrete into planetessimals • Run-away growth • Planetessimals grow into planetary embryos • Gas blown out of system due to high solar winds • Planetary embryos grow into planets • Moon to Mars sized • 10-100 Ma • 10-15 planetary embryos in inner solar system Images from: http://en.wikipedia.org/wiki/Solar_System and http://csep10.phys.utk.edu/astr161/lect/solarsys/nebular.html

  9. Summary • 1) Solar System formed from collapse of interstellar molecular cloud • Heats up and vaporizes all dust • 2) As nebula cools down, condensation of solid materials • Most refractory elements first, followed by more and more volatile elements • 3) Solids accrete in run-away growth • Dust balls • Planetessimals • Planetary Embryos • Planets

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