class 9: icy moons and space junk. today’s topics: galilean moons: io, europa, ganymede, callisto...
TRANSCRIPT
Class 9: Icy Moonsand 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 Moonsand Space Junk
• Asteroids
• Meteor-stuff
• Comets
Moon Size Comparis
on.
IoEuropa
Ganymede Callisto
Titan
Triton
Charon
Jovian Moons = Galilean Moons
Orbit Orbit Diameter Diameter Mass MassDensityDensity
(days)(days) (Moon = 1) (Moon=1) (Moon = 1) (Moon=1)(g/cm(g/cm33))
IoIo 1.81.8 1.01.0 1.21.2 3.53.5
EuropaEuropa 3.63.6 0.90.9 0.70.7 3.03.0
GanymedeGanymede 7.27.2 1.51.5 2.02.0 1.91.9
CallistoCallisto 16.716.7 1.41.4 1.51.5 1.81.8
Jovian Moon Comparison
Exploration
Galileo’s notes
Voyager 1
Galileo spacecraft
Internal Structure
Tidal Heating
Io
Tides on Io
Plumes on Io: How?
Volcanism & Impact Craters on Io
Europa
Brittle Surface Ice
Europa’s Subsurface Ocean?
Liquid?
Brittle Surface Ice
Warm, Convecting Ice?
Evidence for Europa’s Subsurface Ocean
Europa’s Surface Features
RidgesRidgesSpotsSpots IcebergsIcebergs
CratersCraters Bright BandsBright Bands
Ganymede
Ganymede’s Grooved Surface
Ganymede’s Magnetic Field:
(GeologicallyAlive?)
Callisto
Callisto: Geologically Dead
Callisto’s Icy, Cratered Surface
• How many?
Saturn’s Moons
most geologically dead cracks: Tethys, Mimasfew craters: Enceladus
TITAN??
New moon: S/2004S2
8/16/04Cassini48 total (15 major)
3 - 5100 km (Titan)
inside/outside rings
icy (small amounts of rock)
• How large?
• Where?
• Composition?
• Activity?
Titan
Titan’s Atmosphere
Probe descent: January 14, 2005
Huygens Probe Descent
Titan
~10 km
Huygens Probe on Titan
Landing site
Titan’s Surface
Asteroids
Ida
Gaspra
Mathilde
Asteroid Locations
NEAs This Week
http://neo.jpl.nasa.gov/ca/
Size > 1 km = globally destructive
A Bad Day…. 65 Million Years Ago
Chicxulub
Asteroid Shapes & Sizes
Mars
Asteroid Distances
Mini Moons of Asteroids
small moon (1.5 km)
Ida (100 km)
Asteroid Mission: NEAR
Eros gravity
close-upimage
Upcoming Mission: DAWN
Ceres
Vesta
Meteor-stuff
Peekskill, NYAugust 1992
Incoming Debris
Definitions
Meteor Showers
Leonids, 11/2001 Perseids, 8/2004
Earth’s largest meteorite….thus far
Hoba MeteoriteNamibia 66-110 tons
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?
MeteorCrater
Northern Arizona
Wolfe Creek, Australia
Manicouagan, Quebec, Canada
Clearwater Lakes, Quebec, Canada Gosses Bluff, Nor. Territory, Australia
More Terrestrial Craters
Donahue meteoritePeekskil 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 & Misses
Comets
May 7, 2004
Anatomy of a Comet
Head
Tail
GasTail
Comet West
nucleusNucleus:
Comet Head
nucleus surface
coma
Comet Tails
Comet Tails & the Sun
Where do comets originate? (I)
SednaHalley’s Comet
Where do comets originate? (II)
Comet Hyakatuke
Comet Hale Bopp
Comet Shoemaker-Levy 9