3. Center for Lunar Origin and Evolution (CLOE)
History of Impacts on Our Moon
Late heavy bombardment (many
large basins forming in a short time)
-> “Nice” model or end of
accretion?
Goal: Learn more about how our Moon formed and
changed in its early history
4. Center for Lunar Origin and Evolution (CLOE)
History of Impacts on Our Moon
Late heavy bombardment (many
large basins forming in a short time)
-> “Nice” model or end of
accretion?
Goal: Learn more about how our Moon formed and
changed in its early history
5. Center for Lunar Origin and Evolution (CLOE)
1) History of Impacts on Our Moon
explore different rates of impacts
Computer models constrained by new information about evolution of comet
and asteroid populations
Analyze chemistries and ages of early Earth and Moon rocks
Analyze new images of Moon's surface to create a timeline of impact craters
2) Formation of Our Moon: Giant Impact Theory
How the disk evolved into the Moon we see today
Study physics of the disk -> motion, temperature
Powerful computer models constrained by information about chemistry of
early Earth and Moon rocks
Goal: Learn more about how our Moon formed and
changed in its early history
7. Properties of the Moon
Mass ratio of Earth to Moon -> large moon
Moon formed near a rapidly-rotating Earth -> 5 vs. 24 hours
Moon is depleted in iron
8. Giant Impact Model of Moon Formation
Mars-sized body
hits Earth obliquely
& Moon forms from
debris disk
Iron core / stony mantle
Animation from Robin Canup
Early Earth
This model explains:
Mass ratio Earth-Moon
Earth fast rotation speed
Lack of iron in Moon
10. Sea of bodies:
• Moon to Mars-sized
• smaller planetesimals
⇒ MANY
COLLISIONS
Distance From Sun (Further)
(Closer)
Elongation
of
Orbit
Very
Circular
Very
Elongated
Location of
Asteroid Belt
Animation from Alessandro Morbidelli
Large impacts are common!
Jupiter
11. Lunar Accretion Simulations
• Models allow us to track disk
particles forming into Moon
• The Moon could form in as
short as a few years or as long
as 10,000 years
12. Issues
Moon forms too fast and hot => completely molten
– oxide, siderophile, and volatile ratios different than
expected (e.g., water!)
– diversity of basalts
– crust too thin
– global cracks from cooling
New computer model
Late veneer
~ 80% of material from impactor, but Earth-Moon
oxygen isotope ratios identical
Editor's Notes
And mass ratio of earth-moon
Simple Question: Is the angle of the impactor important?