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Our story begins nearly 4.6 billion years ago... Solar System Formation 4.56 billion years ago Q: From what materials is our solar system made? Chondrite –composition roughly equal to that of the Earth. This is a slab of NWA 2089 (LL3) Meteorites Anatomy of a chondrite www.arizonaskiesmeteorites.com CAI’s: Calcium Aluminum-rich inclusions, varying size of material that condensed at T> 1100ºC Chondrules: rounded grains rich in silicon, condensed between 400-900 ºC. Matrix: low temperature silicon and carbon rich phases, condensed below 175 ºC. Carbonaceous Chondrite – likely composition of the Sun without light elements. This is a piece of the Allende Meteorite from Chihuahua, Mexico Chondrites are fragments of the most primitive pieces of our solar system. Compared composition Meteorites Iron-nickel - likely composition of the Earth’s core. Etched Widmanstatten exsolution texture Stony iron – mixed composition of olivine and iron Glorieta Mountain pallasite (NM) www.arizonaskiesmeteorites.com E.B. Watson r = 6378 km The structure of Earth is thought to be very similar to the rest of the terrestrial planets. ] Iron (w 10% Nickel) core ] Fe-Mg Silicate mantle ] Al Ca / K-Na Silicate crust The magnetic fields of Earth and Mercury may result from the liquid state of their cores. Chondrites become attracted and attach Growth continues with impacts - heating, rounding with size When a body is larger than 100 km diameter and hot, iron and other heavy compounds sink towards center, silicon-oxygen compounds float towards surface. Meteorites Achondrite – fragments of the Moon, Mars, and 4 Vesta. This is Martian Shergottitic Meteorite: Dar Al Gani (DAG) 476 from Lybia Achondrite – fragments of the Moon and Mars Allan Hills 84001 A fragment of Mars found in the Antarctic ice. Carbonate concretions Q: What is the evidence for life on Mars? Asteroids Smaller fragments of condensed solid matter Most orbit sun between Mars and Jupiter Infrequently impact planets E.B. Watson E.B. Watson http://near.jhuapl.edu/ http://neo.jpl.nasa.gov/orbits A chilling vision of things to come… 2036 potential impact from Asteroid Apophis (d = 390m) April 13, 2029 enters lowearth space (beneath g.s. satellites). But not hit Earth However, the close encounter will influence its path. If it flies through a 600 m area it will hit the Earth in 2036. (1:45,000 chance) This might hurt a bit… Comets – mostly water ice Image of C/2002 C1 (Ikeya-Zhang) March 11.77, 2002 UT with deltagraph 300/1000 8 min. Ektachrome 100 film Copyright ©2002 Michael Jager. http://encke.jpl.nasa.gov/Recent_Images.html Concentrated at the edge of solar system (Oort Cloud) A few make closer orbits to the sun Watson Kuiper belt - objects outboard of Neptune, butE.B. inside the Oort cloud. Includes Pluto and Charon. Centaurs - between Saturn and Neptune Comets are potential meteorite sources July 20, 1994 Shoemaker-Levy 9 A disaggregated comet stuck Jupiter Bright area is a little bigger than the Earth Earth’s Moon Avg. distance = 380,000 km (238,00 mi) Surface •Orange glass – volcanic NASAGalileo •Basalt – dark colored volcanic rock •Anorthosite – light colored rock that crystallized beneath the sruface •Breccias – mixed rock JSC/NASA •Regolith - fine powder dust •Impact Theory – Mars-sized object strikes Earth, ejects lunar material © 2006, NASA Moon’s composition indicates that formation must occur after partial differentiation of the earth Q: How do we currently think our moon formed? Why? Our story begins nearly 4.6 billion years ago... The MER-A Spirit Meteor Crater, AZ . New computations point to an origin in the impact of a fragmented, nickel-iron meteorite about 50,000 years ago. USGS / David Roddy Tektites Glass fragments (typically small) produced from a meteor impact. The origins are somewhat debatable - chemically linked to the earth, but proximal to impact? (c) 2000 Andrew Alden Recognized Strewnfields Chondrite Dar al Gani, Saharmet.com Planetary building blocks This high-Fe example has spherules of and chondrules rimmed by Fe-Ni aloy After Press & Sevier,1986 10 Liquid 1500 1400 40 50 1300 1200 Solid solution of Ni in g-Fe (FCC) taenite 1100 1000 900 800 nasa.gov Temperature ºC The Willamette Meteorite AMNH octahedrites 700 600 ataxites 500 a-Fe 400 BCC 300 kamacite 200 100 www.alaska.net/~meteor 0 Weight % Ni 20 30 hexahedrites Remote sensing tutorial, 1600 Iron Meteorites 345 10 20 30 Atomic % Ni 40 50 /rochermichel.free.fr/ Number 50 40 30 20 10 10 Liquid 1500 1400 40 Gibeon IVA 50 1300 1200 Ni in g-Fe taenite 1000 900 Kamacite 800 700 600 500 400 300 200 100 light kamacite bands bordered by darker taenite Taenite Ni concentration Temperature ºC 1100 www.alaska.net/~meteor 1600 0 Weight % Ni 20 30 T0 T1 T2 T3 T4 a-Fe 10 20 30 Atomic % Ni 40 50 Kamacite Distance Modified from Watson, 2004 Cape York Meteorite Other elements exhibit similar or inverted concentration patterns From Watson, 2004 Pt-group siderophiles, like Pt, Pd, Ir, Au, are partitioned into taenite in many iron meteorites. In other meteorites, such as Toluca and Cape York, Ir and Pt partitions weakly into kamacite (McDonough et al., 1999). From Cambell and Humayun, 2004 (a) W-Re Thermocouple MgO capsule (b) Pyrex Sleeve 00 14 Graphite Furnace FeNi powder MgO capsule (c) (d) 1380 Vaccum Evaporator Pt and Ir Sputter Coating Au-Pd Target Ceramic tube Short duration runs 5 min-60 min Ceramic “wool” insulation Low temperature 500 ºC - 1000 ºC Heating Element Thermocouple Sample in glass capsule Sample is sealed under ~1 Torr vacuum Steel casing 800 C o SSR 765 C o T P S Wt % Ni 0 Temperature ºC 1600 10 20 30 40 50 Liquid 1400 Fabrication 1200 Solid solution of Ni in g-Fe (fcc) 1000 Au&Pd 800 Diffusion Anneals TCa 600 Pt Martensite BCC tetragonal needles in FCC gamma Fe (Austenite) AS 400 a-Fe bcc 200 MS 0 Ir 10 20 TCg 30 Atomic % Ni 40 50 Film 1E0 Semi-infinite Fe-Ni Alloy 5 E-20 0 1-d diffusion into 0 50 nm Concentration independent 100 0 initial concentration Rutherford Backscattering Curve fitting and D infinite source finite source surface evaporation Arrhenius plots T ºC g As g+a T ºC 1000 900 a 800 700 Ms 600 g As g As 500 g+a g+a Arrhenius parameters Element Au Pd 7 9 11 13 15 Alloy Ea (kJ/mol) Do (m2/s) Fe5%Ni Fe10%Ni Fe20%Ni Fe5%Ni Fe10%Ni Fe20%Ni 117 ± 12 188 ± 14 177 ± 50 107 ±13 166 ± 23 145 ± 72 2.5 (+7.4 / - 3.1) E-12 1.5 (+5.7 / -1.9) E -8 4.1 (+1600 / -4.1) E-9 1.6 (+6.1 / -1.9) E-12 1.4 (+18 / - 1.5) E-9 5.3 (+51000 / -5.3 ) E-11 Arrhenius plots T ºC 1400 1200 5 7 9 11 13 1000 800 700 600 500 Righter et al., 2004, concluded that short-duration, rapid cooling best explains the zonation in Ir and Ni recorded in some of the chondrite grains. These are based on down-T extrapolation of their data which yields lower D.