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 3

Timing of Core formation

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 9

Earth Structure

Slide 10

Ray Paths

Slide 11

D’’ Heterogeneity

Slide 12

Great Earthquakes

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 14

Pallasites: Asteroid Core-Mantle Boundary

Brenham

Slide 15

Old Lunar Highland 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)

Slide 17

Temp

Slide 18

Temp

Slide 19

Temp