Earth - To be described in the next 28 lectures of GSC 20. The moon's crust, a vast panorama of craters, fractures, and lava flows, is four times thicker than earth's. Vast mare areas, composed of dark basalts, smudge the familiar near side of the moon. Brighter highlands dominate the far wide, where a suspected thicker crust may have checked the flow of mare material to the surface. Interior heat from radioactivity causes partial melting, and basaltic material rises along fractures, filling the basin layer by layer to form a mare.
Internal heat drives the turbulence.
Below the atmosphere is a sea of liquid hydrogen and helium. Io - Youngest surface in the solar system. Erupts continually heated by gravitational tugs from Jupiter and Europa. Displays three types of plumes based on interactions between its molten silicate interior, sulfurous mantle, and hard sulfur crust. Streaks that paint the surface were probably fissures in the surface ice that were filled by upwelling water or soft ice.