News
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Exam 4/Final is Saturday December 9 at 2:00 p.m. here in
Clark 107
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A review session will be held on Friday December 8 at 5:15 p.m. (most
likely here in this room)
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A sheet of review questions is available as usual
Extra credit assignments should be turned in no later than the
time of the final exam.
Solar System Debris:
Comets and Asteroids
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Primarily found in two zones in the solar system.
The Asteroid
Belt (rocky,
between
Jupiter and Mars)
The
Edgeworth/Kuiper
Belt (icy, beyond
Neptune – source
of comets)
Solar System Debris:
Comets and Asteroids
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Why do these things exist?.... Solar system formation is a
messy process.
Solar System Debris:
Comets and Asteroids
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Planets sweep up and fling out most of the debris but stable
zones remain.
Solar System Debris: Comets and Asteroids
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Jupiter interfered with the formation of a planet between Mars
and Jupiter. Some fraction of the debris remains today as the
asteroid belt.
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Jupiter stirred up the planetesimals so that collisions were violent rather
than gentle.
Solar System Debris: Comets and Asteroids
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Beyond the orbit of Neptune material was sparse and planetary
accumulation times were very slow. Some icy planetesimals
remain.
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Occasionally one has an orbit modified so that it falls into the inner Solar
System. Warmed by the Sun, ices sublimate away and dust is released
making a “ comet” .
Asteroids
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Asteroids are small, rocky, cratered and irregularly shaped.
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They are the collisionally modified remains of leftover planetesimals
between the orbits of Mars and Jupiter.
Asteroids
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Asteroids are small, rocky, cratered and irregularly shaped.
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They are the collisionally modified remains of leftover planetesimals
between the orbits of Mars and Jupiter.
Asteroids
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Asteroids are small, rocky, cratered and irregularly shaped.
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Asteroids are irregularly shaped because they are basically big rocks.
Their gravity is insufficiently strong to deform them into a spherical
shape.
Asteroids
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Millions of these objects orbit in the Asteroid belt – staying
between Mars and Jupiter.
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Some have orbits that cross the inner planets.
Asteroids
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Some asteroids are “ binary” objects.
Asteroids
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The original “ parent bodies” that were the predecessors of the
asteroids were large enough to differentiate.
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some asteroids are metallic, consisting of the core fragments of a large
parent body.
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the largest asteroids may be intact parent bodies. An upcoming space
mission (DAWN) targets two of the largest – Ceres and Vesta.
Asteroids and Meteorites
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Meteorites that fall to are just small asteroids. They tell the
story of the differentiation and fragmentation of the asteroids.
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Some are entirely metallic, some are stony, some appear to come from
unmodified undifferentiated objects.
Asteroids and Meteorites
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Meteorites that fall to are just small asteroids. They tell the
story of the differentiation and fragmentation of the asteroids.
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Some are entirely metallic, some are stony, some appear to come from
unmodified undifferentiated objects.
Asteroids and Meteorites
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Meteorites that fall to are just small asteroids. They tell the
story of the differentiation and fragmentation of the asteroids.
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Meteorites are often spectral fingerprint matches to distant asteroids.
You can hold a piece of Vesta in your hand with certainty.
Meteorites
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There are four major classes of meteorites
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Stones: rocky meteorites with iron flecks.
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Stones represent the majority of “ falls” but are found in equal numbers
with “ iron” meteorites.
Meteorites
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There are four major classes of meteorites
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Stones tend to be composed of chondrules – glassy beads making up
most of the mass of the rock.
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Astronomers still argue about the origin of chondrules – how did these
glassy beads form during the formation of the Solar System?
Meteorites
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There are four major classes of meteorites
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Irons represent the other significant type of meteorite.
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Only about 6% of “ falls” are irons, but they represent the majority of
“ finds” because they are so recognizable as something completely odd.
Meteorites
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There are four major classes of meteorites
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Irons represent the other significant type of meteorite.
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When etched with nitric acid a crystalline patter appears in cross
sections of iron meteorites.
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This pattern can only arise from the slow cooling of molten iron (one
degree every million years) consistent with formation in the center of a
huge differentiated asteroid!
Meteorites
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There are four major classes of meteorites
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“ Stony-iron” meteorites (a.k.a. Pallasites) appear to have come from the
core-mantle boundary in a differentiated asteroid. They are quite rare.
Meteorites
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There are four major classes of meteorites
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“ Carbonaceous chondrites are possibly the most interesting of
meteorites of all. They represent about 1% of falls.
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Carbonaceous chondrites are undifferentiated and largely unprocessed.
They must come from small parent objects too small to become hot and
melt and differentiate.
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Some carbonaceous chondrites contain amino acids formed in the Solar
Nebula – the building blocks of protiens.
Meteorites
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Meteorites are important astronomically because they represent
material preserved from the time of the origin of the Solar
System.
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Recall that radioactive dating uniformly finds an age of 4.56 billion years
for all of these objects.
Meteorites
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A few, exceptionally rare, meteorites originate from the surface
of the Moon and Mars.
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Impacts launched these rocks into interplanetary space.
Meteorites
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If you want to find a meteorite, go to a place on Earth where
Earth-rocks are rare.
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Antartica and the Sahara Desert are good choices.
Comets
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Icy leftovers of the formation of the Solar System residing
beyond the orbit of Neptune but occasionally falling into the
inner Solar System
The Asteroid
Belt (rocky,
between
Jupiter and Mars)
The
Edgeworth/Kuiper
Belt (icy, beyond
Neptune – source
of comets)
Comets
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Comets are basically “ dirty snowballs” a few kilometers in size.
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During the brief time they are close to the Sun, water and CO2 are
vaporized and create a cloud of gas and dust around the tiny nucleus.
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Pushed away from the Sun by the solar wind and sunlight, this tenuous
debris can stretch a distance equal to the diameter of the Earth's orbit.
Comets
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Comets are basically “ dirty snowballs” a few kilometers in size.
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Comets have two tails
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A gas tail pushed directly away from the Sun by solar wind and
sunlight
A dust tail also pushed away from the Sun, but with some memory of
the comet's path.
Comets
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Comets are basically “ dirty snowballs” a few kilometers in size.
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Comets have two tails
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A gas tail pushed directly away from the Sun by solar wind and
sunlight
A dust tail also pushed away from the Sun, but with some memory of
the comet's path.
Comets
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Comets are basically “ dirty snowballs” a few kilometers in size.
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The comet's nucleus is just a few kilometers in size, but is the source of
all of the interesting phenomena.
Comets
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Comets originate in the “ Oort Cloud” and the Edgeworth/Kuiper
belt.
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Collisions and gravitational tugs can send them falling into the inner
solar system.