1 Class 9: Icy Moons and Space Junk Today’s topics: • Galilean moons: Io, Europa, Ganymede, Callisto • Saturn’s moon: Titan Class Updates • Reading: 23.4-23.5, 23.7 • Homework 4 assigned, due next Monday • Midterm next Monday, April 18th • Midterm review material posted on website Class 9: Icy Moons and Space Junk • Asteroids • Meteor-stuff • Comets Moon Size Comparison . Io Europa Ganymede Callisto Titan Triton Charon2 Jovian Moons = Galilean Moons Jovian Moon Comparison Exploration Galileo’s notes Voyager 1 Galileo spacecraft3 Internal Structure Tidal Heating Io4 Tides on Io Plumes on Io: How? Volcanism & Impact Craters on Io5 Europa Brittle Surface Ice Europa’s Subsurface Ocean? Liquid? Brittle Surface Ice Warm, Convecting Ice? Evidence for Europa’s Subsurface Ocean6 Europa’s Surface Features Ganymede Ganymede’s Grooved Surface7 Ganymede’s Magnetic Field: (Geologically Alive?) Callisto Callisto: Geologically Dead8 Callisto’s Icy, Cratered Surface • How many? Saturn’s Moons most geologically dead cracks: Tethys, Mimas few craters: Enceladus TITAN?? New moon: S/2004S2 8/16/04 Cassini 48 total (15 major) 3 - 5100 km (Titan) inside/outside rings icy (small amounts of rock) • How large? • Where? • Composition? • Activity? Titan9 Titan’s Atmosphere Probe descent: January 14, 2005 Huygens Probe Descent Titan ~10 km Huygens Probe on Titan Landing site10 Titan’s Surface Asteroids Ida Gaspra Mathilde Asteroid Locations11 NEAs This Week http://neo.jpl.nasa.gov/ca/ Size > 1 km = globally destructive A Bad Day…. 65 Million Years Ago Chicxulub A Bad Day…. 65 Million Years Ago Asteroid Shapes & Sizes Mars12 Asteroid Distances Mini Moons of Asteroids small moon (1.5 km) Ida (100 km) Asteroid Mission: NEAR Eros gravity close-up image13 Upcoming Mission: DAWN Ceres Vesta Meteor-stuff Peekskill, NY August 1992 Incoming Debris14 Definitions Meteor Showers Leonids, 11/2001 Perseids, 8/2004 Earth’s largest meteorite….thus far Hoba Meteorite Namibia 66-110 tons15 Moon (meteor showers only) Mars Asteroid Vesta Origins & Ages of Meteors • Stony-Iron (2% falls, 8% finds) – asteroid core/mantle? Compositions (glassy beads, grains) (carbon, volatiles) • Stones (92% falls, 26% finds) – rocky material (silicates) – ancient solar system – Carbonaceous chondrites • Irons (6% falls, 66% finds) – like Earth core (melting) – debris asteroid core? Bill Cassidy Where are meteorites found?16 Meteor Crater Northern Arizona Wolfe Creek, Australia Manicouagan, Quebec, Canada Clearwater Lakes, Quebec, Canada Gosses Bluff, Nor. Territory, Australia More Terrestrial Craters Donahue meteorite Peekskil Chevy • Human strike: Annie Hodges; Sylacauga, AL; bruised; 11/30/54 • Animal strike: Dog; Nakhla, Egypt; 6/24/11 • Structures: Donahue home; Wethersfield, CT; 11/8/82 Chevrolet; Peekskil, NY; 8/9/92 Hits & Misses17 Comets May 7, 2004 Anatomy of a Comet Head Tail Gas Tail Comet West nucleus Nucleus: Comet Head nucleus surface coma18 Comet Tails Comet Tails & the Sun Where do comets originate? (I) Sedna Halley’s Comet19 Where do comets originate? (II) Comet Hyakatuke Comet Hale Bopp Comet Shoemaker-Levy