Class 22: Space Junk (I)
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Class 22: Space Junk (I)
Class Updates
• Reading: 23.10
• Lecture schedule update
• Homework & Exams returned
Today’s topics:
• Asteroids
• Meteor-stuff
• Comets
Asteroids
Ida
Mathilde
Gaspra
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
close-up
image
Eros gravity
Eros Up Close
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Upcoming Mission: DAWN
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Vesta
Ceres
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Meteor-stuff
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Incoming Debris
Peekskill, NY
August 1992
Definitions
Challenge Question
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.
Which of these is the proper scientific
name of your discovery?
a.
b.
c.
d.
Comet
Meteoroid
Meteor
Meteorite
Meteor Showers
Leonids, 11/2001
Perseids, 8/2004
Earth’s largest meteorite….thus far
Namibia
66-110 tons
Hoba Meteorite
Origins & Ages of Meteors
Asteroid Vesta
Mars
Moon
(meteor showers only)
Compositions
•
Irons (6% falls, 66% finds)
– like Earth core (melting)
– debris asteroid core?
• Stones (92% falls, 26% finds)
– rocky material (silicates)
– ancient solar system
– Carbonaceous chondrites
(carbon, volatiles)
(glassy beads, grains)
• Stony-Iron (2% falls, 8% finds)
– asteroid core/mantle?
Where are meteorites found?
Bill Cassidy
Meteor
Crater
Northern Arizona
More Terrestrial Craters
Wolfe Creek, Australia
Manicouagan, Quebec, Canada
Clearwater Lakes, Quebec, Canada
Gosses Bluff, Nor. Territory, Australia
Hits & Misses
•
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
Donahue meteorite
Peekskil Chevy
Comets
May 7, 2004
Anatomy of a Comet
Gas
Tail
Tail
Head
Comet West
Comet Head
nucleus
Nucleus:
nucleus surface
coma
Nucleus: Comet Wild 2
Comet Tails
Sunlight = Tails (movie)
Where does gas tail point?
Where do comets originate? (I)
Halley’s Comet
Sedna
Where do comets originate? (II)
Comet Hyakatuke
Comet Hale Bopp
Comet Shoemaker-Levy 9
Review
Which is which?
2
1
3
a.
b.
c.
d.
(1) comet; (2) meteor; (3) comet
(1) asteroid; (2) meteor; (3) comet
(1) comet; (2) asteroid; (3) meteor
(1) meteor; (2) asteroid; (3) comet
Challenge Question
Tunguska, Russia
On the morning of June 20, 1908 witnesses described a brilliant
fireball, brighter than the Sun, streak across the sky. Still descending, it exploded with a blinding flash & an intense pulse of
heat. The blast was heard up to 1000 km away; the resulting
pulse of air pressure circled Earth twice. 1000s of tons of a
powdery material resembling carbonaceous chondrites were later
found scattered in the soil.
What do you think was the likely
source of the Tunguska event?
Trees flattened out to 30 km