Orbit diameter density atmosphere of light elements n2

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Unformatted text preview: y ~500 million years, no old craters on surface Terrestrial Planets: Earth ! Orbit: Diameter: Density: ! Atmosphere of light elements ! ! • • ! N2, O2, trace CO2 Significant water vapor, liquid water at surface Higher volatile content than Venus • • • ! 1.00 AU 12,103 km 5.52 g/cc Greater distance from Sun diminished photolytic decomposition of water in atmosphere Cooler surface temperature allowed condensation of liquid water, forming a surface reservoir 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: Diameter: Density: ! No atmosphere, no volatiles at all ! ! • ! 384,400 km from Earth 3,476 km 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 Highlands • Brighter regions, older than mare basins, composed chiefly of anorthosite gabbro Regolith • Surface of moon is covered by a fine-grained, pu...
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