Class 22: Space Junk (I)

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Class 22: Space Junk (I)

Today’s topics: • Asteroids• Meteor-stuff• Comets

Class Updates• Reading: 23.10• Lecture schedule update• Homework & Exams returned

Asteroids

Ida

Gaspra

Mathilde

Asteroid Locations

NEAs This Week

http://neo.jpl.nasa.gov/ca/

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

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Eros Up Close

Upcoming Mission: DAWNQuickTime™ and a

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Ceres

Vesta

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Meteor-stuff

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Peekskill, NYAugust 1992

Incoming Debris

Definitions

Suppose that you are hiking along the icy banks of an Antarctic glacier and you stumble upon a very odd looking rock, which you

later confirm to be a chunk of an asteroid that fell to Earth.

a. Cometb. Meteoroidc. Meteord. Meteorite

Which of these is the proper scientificname of your discovery?

Challenge Question

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, AustraliaManicouagan, 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 & Misses

Comets

May 7, 2004

Anatomy of a Comet

Head

Tail

GasTail

Comet West

nucleusNucleus:Comet Head

nucleus surface

coma

Nucleus: Comet Wild 2

Comet Tails

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Sunlight = Tails (movie)

Where does gas tail point?

Where do comets originate? (I)

SednaHalley’s Comet

Where do comets originate? (II)

Comet Hyakatuke

Comet Hale Bopp

Comet Shoemaker-Levy 9

12

3

Which is which?

a. (1) comet; (2) meteor; (3) cometb. (1) asteroid; (2) meteor; (3) cometc. (1) comet; (2) asteroid; (3) meteord. (1) meteor; (2) asteroid; (3) comet

Review

On the morning of June 20, 1908 witnesses described a On the morning of June 20, 1908 witnesses described a brilliant brilliant

fireball, brighter than the Sun, streak across the sky. Still fireball, brighter than the Sun, streak across the sky. Still de-de-

scending, it exploded with a blinding flash & an intense scending, it exploded with a blinding flash & an intense pulse ofpulse of

heat. The blast was heard up to 1000 km away; the heat. The blast was heard up to 1000 km away; the resultingresulting

pulse of air pressure circled Earth twice. 1000s of tons of apulse of air pressure circled Earth twice. 1000s of tons of apowdery material resembling powdery material resembling carbonaceouscarbonaceous chondriteschondrites

were laterwere laterfound scattered in the soil. found scattered in the soil.

What do you think was the likely source of the Tunguska

event?

Trees flattened out to 30 km

Tunguska, RussiaChallenge Question