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