Transcript 15asteroids4s

Asteroids
Astronomy 311
Professor Lee Carkner
Lecture 15
Quiz #2 Monday
Quiz 2 same format as quiz 1
~20 multiple choice/matching
~4 short answer
Covers lectures 9-15
bring pencil and calculator
No class Friday
Rocks in Space
Asteroid -Meteoroid -Meteor -- the flash of light when a
meteoroid hits the Earth’s atmosphere
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sometimes called a falling or shooting star
Meteorite --
Types of Meteorites
Meteorites are classified based on their
composition
Two major types are irons and chondrites
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Chondrites are the most common type of
meteorite
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But, irons are much easier to find
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What are the properties of chondrites and
irons and how can you identify them?
Iron Meteorites
Composed of iron and nickel
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Often show Widmanstatten patterns
when etched with acid
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Widmanstatten Paterns
Chondrite (Stony) Meteorites
Composed of silicates
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Contain chondrules, small glassy
inclusions of material that were heated
and quickly cooled
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Carbonaceous chondrites
Chondrules
The Missing Planet
In the 18th century astronomers noticed that
there was a gap between Mars and Jupiter
with no planets
In 1801 G. Piazzi found a faint moving star in
the gap
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This is the asteroid belt
The Asteroid Belt
Asteroid Myths
Are the asteroids debris from a planet
that exploded?
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Is the asteroid belt dangerous to travel
through?
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Asteroid Facts
Size:
Orbit: Asteroid Belt 2-3.5 AU, some
have eccentric Earth crossing orbits
Description:
Formation of the Asteroid Belt
If Jupiter did not exist, a fifth terrestrial
planet might have formed at 2.8 AU
Jupiter’s gravity:
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Trojans and NEOs
Many asteroids are found outside of the asteroid
belt
Trojan asteroids have been captured in Jupiter’s
Lagrange points
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Some asteroids cross the Earth’s orbit and are
called Near Earth Objects (NEO)
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Studying Asteroids
Several asteroids have been observed at
close range

In 2005 the Japanese mission Hayabusa
studied asteroid Itokawa and tried to
collect a sample for return to Earth
Asteroid Features
Only Ceres, Pallas and Vesta (the 3
largest asteroids) have enough gravity
to form a sphere
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Asteroids show many craters
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During the heavy bombardment period
asteroid collisions must have been frequent
Composition of Asteroids
Asteroids are divided into three major
groups based on composition
S Type
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C Type
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M type
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Formation of Asteroids
M and S type asteroids are found in the
inner asteroid belt where temperatures
are higher
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Formation of Meteoroids
Some asteroids became large enough to
differentiate
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These asteroids were then broken up by collisions
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Asteroids that never differentiated formed
chondrites
What Use is an Asteroid?
Mining
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Space Habitats
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Spaceships
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Providing Material for Life in Space
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Summary
Asteroids are small bodies that orbit the Sun
Most are in the asteroid belt between Mars
and Jupiter (2-3.5 AU)
Jupiter’s gravity prevented the asteroids
from forming a planet
Description:
Small (most less than 1 km)
Max size is few hundred km
Irregularly shaped
Heavily cratered
Summary: Meteoroids
Iron
made of metal
formed from core of
asteroids (M type)
Achondrites (Stony)
made of rock with
no inclusions
made from crust of
asteroids (S type)
Chondrites (Stony)
made of rock with
small inclusions
made from
undifferentiated
asteroids (S and C
type)