Earthlike Planets: Venus and Mars (Astronomy)

Recall cards comparing Venus and Mars, Earth's two nearest planetary neighbors. The bulk and orbital data of each world: distance from the Sun, orbital period, diameter, mass, density, surface gravity, escape velocity, rotation, and surface conditions. The geology of Venus: its lowland lava plains, the absence of plate tectonics, the Aphrodite and Ishtar highlands, the Maxwell Mountains, its shield volcanoes and pancake domes, and how Magellan's radar and the Venera landers explored it. The crushing 90-bar, 96-percent carbon-dioxide atmosphere of Venus, its sulfuric-acid clouds, and the runaway greenhouse effect that makes it the hottest planet. The geology of Mars: Olympus Mons, the Valles Marineris canyons, the Tharsis bulge, its cratered southern highlands, and the Mariner and Viking missions. The evidence for water and life on Mars: its polar caps, runoff and outflow channels, recurring slope lineae, subsurface ice, and ancient lakebeds. And why three planets that began alike diverged into such different worlds.