The Moon Geology, Exploration, Origin

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- possible water ice at poles

- radio waves reflected off ice

• 1998: Lunar Prospector

- also found evidence for ice

- crashed near pole in 1999

• Currently: Smart 1 Probe

- European satellite

- ion propulsion (several months!)

- will search for water at poles

Slide 14

Moon Rocks: Sampling the Surface of the Moon

• surface material: “regolith” –

pulverized by constant impacts

• ~2500 samples brought back

by astronauts; ~850 lbs total!!

• all rocks are IGNEOUS (i.e.,

from molten processes)

• totally dry rocks (no water)

• all rocks older than 3 Byr

Slide 15

Moonquakes: Studying the Moon’s Interior

•~ 3000 quakes/year

•much lower intensity

than Earth: 0.5-1.5 Richter

•indicate that Moon’s

interior is more rigid than

Earth’s (some ‘plasticity’)

Slide 16

Moon’s interior structure

• iron-rich core like Earth

• asthenosphere layer: somewhat pliable “plastic” layer

• solid layer just below surface – no plate tectonics

• smaller planet than Earth – less internal energy, less geological activity!

• moon probably had a weak magnetic field early in history

- core is now solid, so no current is generated

Slide 17

Color-coded images illustrate surface geography

Clementine data

• blue – lowland marias

• red - highlands

Galileo data – flyby in 1989

• blue – lowland marias

• red - highlands

Slide 18

Theories for Origin of Moon

Fission: originally part of Earth but torn free

Problem: would have fallen back or been flung into space, not into orbit.

Fails to explain why lunar chemistry differs from Earth's

Co-Creation: formed in its present orbit

can not explain why lunar chemistry differs from Earth's

Capture: formed as a separate planet but captured by Earth

Conditions for successful capture very stringent

Impact: formed from Mega-Impact of Mars-sized planet

Computer modeling suggests SS forms 100 or so small planets, then collide to make larger objects

can explain differences in chemistry:

impact occurred after chemical differentiation in Earth; therefore, not as much iron was part of the Moon

high temperatures during impact would have vaporized the volatile and water vapor in rocks

Currently favored model

Slide 19

Computer Simulation of Formation of Moon