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Unformatted text preview: y ~500 million years, no old craters on surface Terrestrial Planets: Earth ! Orbit:
Density: ! Atmosphere of light elements !
! N2, O2, trace CO2
Significant water vapor, liquid water at surface Higher volatile content than Venus
• ! 1.00 AU
5.52 g/cc Greater distance from Sun diminished photolytic decomposition of water in
Cooler surface temperature allowed condensation of liquid water, forming a
Sequestration of CO2 in rock prevented runaway greenhouse effect Active volcanism
• Large Fe-Ni core, convecting to produce a magnetic field
Partial melting in upper mantle allows formation of asthenosphere, allowing
tectonic plate motions Terrestrial Worlds: Moon ! Orbit:
Density: ! No atmosphere, no volatiles at all !
! 384,400 km from Earth
3.34 g/cc (possible cometary material present at poles: CO2, H2O ice) Surface features
• • • Mare
• Dark planes, formed by impacts that ruptured the crust, allowing flood
basaltic volcanism to fill impact basins
• Brighter regions, older than mare basins, composed chiefly of anorthosite
• Surface of moon is covered by a fine-grained, pu...
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- Spring '14