GEOL 3045: Planetary GeologyGEOL 3045: Planetary Geology

Lysa ChizmadiaFormation of the

Moon

Lysa ChizmadiaFormation of the

Moon

Lunar EclipsesLunar Eclipses

Images from: http://en.wikipedia.org/wiki/Lunar_eclipse

20 Feb 200820 Feb 2008

http://sunearth.gsfc.nasa.gov/eclipse/LEmono/TLE2008Feb21/TLE2008Feb21.html

Formation TheoriesFormation TheoriesFission: Moon was originally part of the

Earth & somehow separated earlyProblem: compositions not ~ enough

Capture: Moon was created somewhere else and captured by Earth’s gravityProblem: O-isotopes identical

Mutual Accretion: They both formed together out of the same materialsProblem: Moon has little or no core

Big Splash: ~Mars-sized bolide hit Earth & Moon formed from ejecta ringFits O-isotopes, trace elements & low

density of Moon

Fission: Moon was originally part of the Earth & somehow separated earlyProblem: compositions not ~ enough

Capture: Moon was created somewhere else and captured by Earth’s gravityProblem: O-isotopes identical

Mutual Accretion: They both formed together out of the same materialsProblem: Moon has little or no core

Big Splash: ~Mars-sized bolide hit Earth & Moon formed from ejecta ringFits O-isotopes, trace elements & low

density of Moon

Big Splash (1/3)Big Splash (1/3)Impactor ~ size of Mars

Called TethysCollided ~4.4 Ga

Sprayed crust & some of mantle into space

Both proto-Earth & Tethys molten

Core of impactor incorporated into Earth’s core

Impactor ~ size of MarsCalled Tethys

Collided ~4.4 Ga

Sprayed crust & some of mantle into space

Both proto-Earth & Tethys molten

Core of impactor incorporated into Earth’s core

Images from: http://www.psi.edu/hartmann/pic-cat/earth.html

Big Splash (2/3)Big Splash (2/3)Ejecta from impact forms

ring around molten EarthBoth have magma oceans

Ring coalesces into Moon

Crust of both bodies cool downNo longer magma oceans

Moon sweeps up rest of ring material

Ejecta from impact forms ring around molten EarthBoth have magma oceans

Ring coalesces into Moon

Crust of both bodies cool downNo longer magma oceans

Moon sweeps up rest of ring material

Images from: http://www.psi.edu/hartmann/pic-cat/earth.html

Big Splash (3/3)Big Splash (3/3)Volcanism on Moon

Late Heavy Bombardment

Volcanism subsides on Moon

Volcanism on Moon

Late Heavy Bombardment

Volcanism subsides on Moon

Images from: http://www.psi.edu/hartmann/pic-cat/earth.html

Late Heavy BombardmentLate Heavy Bombardment3.8 - 4.1 MaBasin-forming impacts

on Moon, Earth, Mercury, Venus, MarsE.g. Caloris Basin, Mare

BasinsMaterials sent in to

inner solar system by perturbations from Giant Planets

3.8 - 4.1 MaBasin-forming impacts

on Moon, Earth, Mercury, Venus, MarsE.g. Caloris Basin, Mare

BasinsMaterials sent in to

inner solar system by perturbations from Giant Planets

Image from: http://www.daviddarling.info/encyclopedia/L/late_heavy_bombardment.html

Lunar VolcanismLunar VolcanismMare Volcanism

Most 3.5 - 3.0 GaAges range from 4.2 to 1.2 Ga

Occurs mostly on near sideClassification:

High Ti basaltLow Ti basaltVery low Ti basalt

Ti-rich Orange glass3.7-3.8 Ga

Mare VolcanismMost 3.5 - 3.0 Ga

Ages range from 4.2 to 1.2 Ga

Occurs mostly on near sideClassification:

High Ti basaltLow Ti basaltVery low Ti basalt

Ti-rich Orange glass3.7-3.8 Ga

Images from: http://www.psrd.hawaii.edu/Dec00/highTi.html

KREEPKREEPK = PotassiumREE = Rare Earth

ElementsP = Phosphorus

Formed as a result of magma oceanHeavy minerals (e.g.

olivine, pyroxene) sankLight minerals (e.g.

Plagioclase) roseFractional Crystallization

made magma KREEP-richKREEP = incompatible

K = PotassiumREE = Rare Earth

ElementsP = Phosphorus

Formed as a result of magma oceanHeavy minerals (e.g.

olivine, pyroxene) sankLight minerals (e.g.

Plagioclase) roseFractional Crystallization

made magma KREEP-richKREEP = incompatible

Images from: http://www.lunarpedia.org/index.php?title=KREEP

SummarySummaryFormed from Big Splash

Problems with other modelsMoon ~ Earth composition, but not

identicalMoon has low densityMoon & Earth have same O-isotopes

Heavy Late BombardmentPerturbations from Giant Planets

Lunar VolcanismTi important element

KREEPLeftovers from fractional

crystallization of magma ocean

Formed from Big SplashProblems with other models

Moon ~ Earth composition, but not identical

Moon has low densityMoon & Earth have same O-isotopes

Heavy Late BombardmentPerturbations from Giant Planets

Lunar VolcanismTi important element

KREEPLeftovers from fractional

crystallization of magma ocean