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2-Observational evidence for relative abundances (moon) (Moon elemental…
2-Observational evidence for relative abundances (moon)
Moon Sources
Apollo missions
Monitoring seismic activity
Physical properties like moment of inertia and magnetic field
Moon structure
Crust
60km thick
8% by volume
Thinner on the side facing the earth
Feldspathic, rich in Al, Ca
Mantle/lithoshpere
90% by volume
Core
Probably FeS
Some debate
Density 3500 kg.m-3
Moment of inertia indicates nearly uniform density
No magnetic field now
Probably not pure iron core
Moon elemental content
No water so...
No sedimentary rocks
No minerals formed by hydration
No weathering
No atmosphere so no oxides
Igneous rocks formed by direct crystalisation out of a silicate melt
Lower density rocks frothed up as moon cooled
U,Ti,Zr and REE are more abundant on the moon
CNO Cl, siderophiles, chalcophiles and iron are less abundant
Higher boiling point=more abundant on earth
Nothing indicates earth and moon do not have a common origin
Moon topographical areas
Maria (seas)
Younger (3.5 Gyrs)
Volcanic outflows
Rocks like oceanic crust on earth
Evidence of titanium rich lavas which have rapidly cooled
Highlands
Older rocks 4.5 Gyrs
Ligher in appearance
Lacking iron-rich basalts
Moment of inertia
From measurements of doppler tracking of lunar prospector spacecraft
low circular polar orbit
Measure line of site velocity via doppler shift
Accurate at 10-7 level
Implies small dense core
Maths: