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 –compositionroughly equal to that of theEarth. This is a slab of NWA2089 (LL3)

M

eteo

rites

www.arizonaskiesmeteorites.comAnatomy of a chondrite

CAI’s: Calcium Aluminum-rich inclusions, varying size ofmaterial that condensed at T> 1100ºC

Chondrules: rounded grains rich in silicon, condensedbetween 400-900 ºC.

Matrix: low temperature silicon and carbon rich phases,condensed below 175 ºC.

Carbonaceous Chondrite –likely composition of the Sunwithout light elements. This

is a piece of the AllendeMeteorite from Chihuahua,

Mexico

Chondrites are fragments of the mostprimitive pieces of our solar system.

Compared composition

M

eteo

rites

Iron-nickel - likely compositionof the Earth’s core. EtchedWidmanstatten exsolutiontexture

Stony iron – mixedcomposition of olivine

and iron

Glorieta Mountainpallasite (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 attractedand attach

Growth continues with impacts- heating, rounding with size

When a body is larger than 100km diameter and hot, iron andother heavy compounds sinktowards center, silicon-oxygencompounds float towardssurface.

M

eteo

rites

Achondrite – fragments of the Moon, Mars,and 4 Vesta. This is Martian ShergottiticMeteorite: Dar Al Gani (DAG) 476 fromLybia

Achondrite – fragments of theMoon and Mars

Allan Hills 84001

A fragment of Mars found inthe 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 fromAsteroid Apophis (d =390m)

April 13, 2029 enters low-earth space (beneath g.s.satellites).

But not hit Earth

However, the closeencounter will influence itspath. If it flies through a600 m area it will hit theEarth in 2036. (1:45,000chance)

This might hurt a bit…

Concentrated at the edge of solar system (OortCloud)

A few make closer orbits to the sun

Image of C/2002 C1 (Ikeya-Zhang)March 11.77, 2002 UT with deltagraph 300/1000 8 min.

Ektachrome 100 filmCopyright ©2002 Michael Jager.

http://encke.jpl.nasa.gov/Recent_Images.html

Comets – mostly water ice

E.B. WatsonKuiper belt - objects outboard of Neptune, but insidethe Oort cloud. Includes Pluto and Charon.

Centaurs - between Saturn and Neptune

Comets arepotential meteoritesources

July 20, 1994

Shoemaker-Levy 9

A disaggregatedcomet stuck Jupiter

Bright area is alittle bigger thanthe Earth

Earth’s Moon

NASAGalileo

Avg. distance = 380,000 km(238,00 mi)

Surface

•Orange glass – volcanic

•Basalt – dark colored volcanicrock

•Anorthosite – light coloredrock that crystallized beneaththe sruface

•Breccias – mixed rock

•Regolith - fine powder dustJSC/NASA

•Impact Theory – Mars-sized object strikes Earth, ejectslunar material

Moon’s composition indicates that formation must occurafter partial differentiation of the earth

Q: How do we currently think ourmoon formed? Why?

© 2006, NASA

Our story begins nearly 4.6 billion years ago...

The MER-A Spirit

Meteor Crater, AZ . New computations point to anorigin in the impact of a fragmented, nickel-ironmeteorite about 50,000 years ago. USGS / DavidRoddy

(c) 2000 Andrew Alden

Tektites

Glass fragments (typicallysmall) produced from ameteor impact.

The origins are somewhatdebatable - chemically linkedto the earth, but proximal toimpact?

Recognized Strewnfields

After Press & Sevier,1986

ChondriteDar al Gani, Saharmet.comPlanetary building blocksThis high-Fe example hasspherules of and chondrulesrimmed by Fe-Ni aloy

Iron Meteorites

1020304050

Numb

er

Liquid

345

100200300400500600700800900

1000110012001300140015001600

Solid solution ofNi in g-Fe (FCC)taenite

Atomic % Ni

a-FeBCCkamacite

10 20 30 40 50

0 10 20 30 40 50Weight % Ni

Temper

ature

ºC

Remote s

ensing tu

torial,

nasa.gov

/rocherm

ichel.free

.fr/www

.alaska.n

et/~mete

orhexahedrites

octahedrites

ataxites

The WillametteMeteoriteAMNH

Liquid

100200300400500600700800900

1000110012001300140015001600

Ni in g-Fe taenite

Atomic % Ni

a-Fe

10 20 30 40 50

0 10 20 30 40 50Weight % Ni

Temper

ature º

C

TaeniteKamacite

T0T1T2T3T4

Kamacite

Ni con

centra

tion

DistanceModified from Watson, 2004

Gibeon IVA light kamacite bands bordered by darker taenite

www.alas

ka.net/~

meteor

Cape York Meteorite

From Watson, 2004Other elements exhibit similar or inverted concentration patterns 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

4 01 01380

FeNi powderMgO capsule

Graphite FurnacePyrex Sleeve

MgO capsule

W-ReThermocouple(a) (b)

(c) (d)

Sputter CoatingAu-Pd Target

Vaccum EvaporatorPt and Ir

Heating Element

Sample is sealedunder ~1 Torrvacuum

Steel casing

Thermocouple

Ceramic tube

Ceramic “wool”insulation

o765 CT P S

SSR

o800 C

Sample in glasscapsule

Short duration runs5 min-60 minLow temperature500 ºC - 1000 ºC

Liquid

200

400600

8001000

120014001600

Solid solution ofNi in g-Fe (fcc)

Fabrication

Atomic % Ni

a-Febcc

10 30 40 50

0 10 20 30 40 50Wt % NiTem

peratu

re ºC

DiffusionAnneals

0MS

T gC

T aC

AS

20

Au&PdIrPt

MartensiteBCC tetragonal needles in FCC gamma Fe (Austenite)

100500

1 E 0Film

Fe-Ni Alloy

0 nm

5 E-20

1-d diffusion intoSemi-infiniteConcentration independent0 initial concentration

Rutherford Backscattering

infinite source

Curve fitting and D

finite source

surface evaporation

T ºCT ºC

g g+a aMs

As

g g+aAs

g g+aAs

1000 900 800 700 600 500

13 151197

Arrhenius plots

Arrhenius parameters2Element Alloy Ea (kJ/mol) Do (m /s)Au Fe5%Ni 117 ± 12 2.5 (+7.4 / - 3.1) E-12Fe10%Ni 188 ± 14 1.5 (+5.7 / -1.9) E -8 Fe20%Ni 177 ± 50 4.1 (+1600 / -4.1) E-9Pd Fe5%Ni 107 ±13 1.6 (+6.1 / -1.9) E-12 Fe10%Ni 166 ± 23 1.4 (+18 / - 1.5) E-9Fe20%Ni 145 ± 72 5.3 (+51000 / -5.3 ) E-11

139 115 7

10001200 800 700 600 5001400T ºC

Arrhenius plots

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.