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Exam Review Atmospheres Summary • Surface temperature depends on solar distance, albedo, atmosphere (greenhouse effect) • Scale height and lapse rate are controlled by bulk properties of atmosphere (and gravity) • Terrestrial planetary atmospheres are not primordial – affected by loss and outgassing • Coriolis effect organizes circulation into “cells” and is responsible for bands seen on giant planets • Isotopic fractionation is a good signal of atmospheric loss due to Jeans escape • Significant volatile quantities may be present in the interiors of terrestrial planets Key Concepts • • • • • • • • • • • • Albedo and opacity Greenhouse effect Snowball Earth Scale height H = RT/gm Lapse rate Tropopause Coriolis effect 2 w v sin(q) Hadley cell Geostrophic balance Jeans escape Urey reaction Outgassing Orbits Summary • Elliptical orbits (Kepler’s laws) are explained by Newton’s inverse square law for gravity • In the absence of external torques, orbital angular momentum is conserved (e.g. Earth-Moon system) • Orbital energy depends on distance from primary • Tides arise because gravitational attraction varies from one side of a body to the other • Tides can rip a body apart if it gets too close to the primary (Roche limit) • Tidal torques result in synchronous satellite orbits • Diurnal tides (for eccentric orbit) can lead to heating and volcanism (Io, Enceladus) Key Concepts • • • • • • Angular frequency Angular momentum Tides & diurnal tides Roche limit Synchronous satellite Laplace resonance GM=r3w2 I mr r dm 2 L Iw E= - GM/2r 2 Satellites Summary • For icy satellites, main source of energy is tides – link between orbital and geological evolution • Some show present-day geological activity (Enceladus, Europa, Io, Triton) • Many show ancient geological activity • Oceans are quite common – habitability • Titan is unusual because it has an atmosphere and an active “hydrosphere” (liquid methane) • Likely to be targets for future spacecraft missions Comets Summary • Comets are dirty snowballs with a dark crust • They provide samples of (hopefully) primordial, volatile-rich solar nebula material • SP comets come from the Kuiper Belt • LP comets come from the Oort Cloud • The architecture of the Kuiper Belt is probably a result of Jupiter, Saturn and Neptune moving around early in their history! Asteroids key concepts • • • • • • • • Asteroid belt, Kirkwood gaps Lagrangian points Near earth objects Space weathering Some geologic observations of asteroids Vesta vs. Ceres Chondrules and chondrite meteorites HED meteorites and Vesta