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Slide 1
Observations/Inferences:
Rocky inner, icy outer solar system
Asteroid differentiation temperatures heliocentrically distributed
Gross zonal structure within asteroid belt preserved
The Moon had a magma ocean
The solar photosphere has a composition very similar to CI carbonaceous chondrites
Heat source concentrated near Sun?orLonger times to accrete object farther from the sun (less Al heating)?26
Slide 2
Heat Sources:
Solar/Magnetic Induction heating (but T-Tauri: Polar Flows)
Short-lived radioisotopes (26Al 0.73 Ma half life: must accrete fast)
Long-lived radioisotopes (U, Th, K) (slow, only for larger bodies)
Large impacts (only for larger bodies: between Moon and Mars-sized)
Potential energy of core formation (larger bodies: 6300 km radius: 2300°C rise,
Resonant tidal heating (Only moons: Moon?, Titan, Io, Europa)
3000 km radius: 600°C rise)
Slide 4
Two Possible Mechanisms to Separate Metal from Silicate
Porous Flow Immiscible Liquids and Deformation
Slide 5
Dihedral (wetting) Angle Theory
The Dihedral Angle Theta is a force balance between interfacial energies
Slide 6
Sulfide Melt in an Olivine Matrix
Most Fe-Ni-S melts do not form interconnected melt channels
Slide 7
0
Depthkm
PressureGPa
500
750
250
15
22.5
0
7.5
PressureGPa
after Carlson, 1994
No Crystal Settling
Perovskite SettlingLow Mg/Si
Dunite High Mg/Si
Liquid
Liquid
Liquid
15
22.5
0
7.5
Crystal Cummulates
t Quench CrustQuenchCrust
Magma Ocean Crystallization
Cummulates should give a chemical signature
Slide 8
Lower Mantle Solidus
Pressure (GPa)
2000
Tem
per
atu
re (
K)
3000
4000
5000
200 40 80 120CMB
Mantle Adiabat
solidus (upper bound) Core T
Multianvil Peridotite Solidus
Olivine shock melting
Magnesiowüstite melting
Zerr et al (98), Holland & Ahrens (97)
Diamond Anvil Peridotite Solidus
Slide 13
Samples Recording Planetary Differentiation
4.4
Earliest Solar System Solids (CAIs, Chondrules)
Other Plantary Bodies
Earth's Moon
Earth
2.5 0.10.6Time before present (Ga)
Formation (4.56 Ga)
Chondrite alteration
Achondrites (Vesta and HEDs)
Mars (SNCs)
Highlands
Mare Basalts
Continental Crust
Ocean Crust
Slide 16
An Oblique Collision between the proto-Earth and a Mars-sized impactor
4.2 minutes
8.4 minutes 12.5 minutes
Kipp and Melosh (86), Tonks and Melosh (93)