Download Our story begins nearly 4.6 billion years ago

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.