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- Remnants of Rock and Ice:
- Asteroids, Comets, and Pluto
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- Comets, Asteroids and Meteorites carry the history of our solar system
encoded in their compositions, locations, and numbers.
- Asteroid:
- a rocky leftover planetesimal orbiting the Sun.
- Comet:
- an icy leftover planetesimal orbiting the Sun-regardless of its size or
whether or not it has a tail.
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- Meteor:
- a flash of light in the sky
caused by a particle entering
the atmosphere, whether the particle
comes from an asteroid or a comet.
- Meteorite:
- any piece of rock that fell to the ground from the sky, whether from an
asteroid, a comet, or even another planet.
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- The main Asteroid Belt lies between 2.2 and 3.3 AU from the Sun.
- Origin and Evolution of the
Asteroid belt:
- The Asteroid belt probably formed as a result of orbital resonance.
Resonance occurs whenever one object’s orbital period is a simple ratio
of another object’s period.
- These resonances with Jupiter probably prevented a planet from ever
forming in the region of the Asteroid Belt.
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- Another effect of the resonance is to form gaps in the orbits of the
Asteroids as they orbit the Sun.
- These are called the Kirkwood Gaps.
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- Primitive Meteorites: Most primitive meteorites are composed of rocky
minerals with an important difference from Earth rocks.
- The Primitive Meteorites are our best source of information about
conditions in the solar nebula.
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- A smaller group of meteorites appears to have undergone substantial
change since the formation of the solar system.
- These “Processed Meteorites” apparently were once part of a larger
object that modified the original material into another form.
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- Carbon –rich meteorites came from the outer portion of the asteroid
belt. (> 3AU)
- Carbon – poor meteorites formed in the inner warmer part of the asteroid
belt.
- The processed meteorites have compositions similar to the cores,
mantles, or crusts of the
terrestrial worlds. These are fragments of the terrestrial worlds.
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- Processed meteorites with basaltic compositions must have come from lava
flows.
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- Icy Planetesimals that have been left over from the formation of the
Solar System.
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- Pluto was discovered in 1930 by an American Astronomer named Clyde
Tombaugh.
- Pluto has long been seen to be a misfit among the planets, fitting into
neither the terrestrail nor the jovian category.
- It has a 248 year orbit that is unusually elliptical and significantly
tilted relative to the ecliptic.
- Pluto has a moon – Charon.
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- The numbers of small bodies orbiting the solar system have diminished
significantly since the days of early bombardment, when most impact
craters were formed.
- However, there are still plenty of fragments left and collisions between
these fragments and the planets still occur on occasion.
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- Was shatter by Jupiter’s gravity in 1992.
- All pieces hit Jupiter in the summer of 1994 leaving dark impact scars.
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- Arizona Meteor Crater
- measures 1 mile across
- from an impact 50,000 years ago
- by a 50 meter meteoroid
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