Planetary Geology

accretion albedo anorthositic Apollo 11 Apollo sites areas astronauts atmosphere basalts breccias chondrites chondrules clasts composition Copernicus core Crater material crust crystalline rocks crystals dark density deposits depth diameter differentiation Earth ejecta elements Eratosthenian farside Figure flow formation formed frontside gabbros gases glass heat highlands Imbrium Basin impact craters indicated interior isotopes kamacite kilometers KREEP large craters lavas layers Luna 16 lunar rocks lunar surface magnetic field mantle mare lavas Mariner 9 Mars Martian melting meteorites meters million minerals missions Moon Moon's NASA NASA photo Oceanus Procellarum olivine origin outer particles phase photographs plagioclase planet planetary polar probes Procellarum pyroxene ratios region regolith relative result ridges rilles samples satellite seismic Serenitatis silicates soil solar system solar wind spacecraft structure Surveyor taenite telescope temperatures terra terrain terrestrial thermal thick tion U.S. Geological Survey units variations velocity volcanic zone