Remnants of Rock and Ice

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Remnants of Rock and Ice

• Remnants of Rock and Ice
• Asteroids, Comets, and Pluto

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Remnants from Birth

• 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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Asteroids
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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
  objects orbital period is a simple ratio of
  another objects 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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The Kirkwood Gaps
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Asteroids are recognizable in telescope images
because they move relative to the stars in just a
short time.
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See SFA Observatory
SFA Observatory Asteroid Discoveries
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Gaspra (16 km across) Galileo
Ida(53 km) and its tiny moon Galileo
Mathide(59 km) NEAR
Eros (40 km) NEAR
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Meteorites

• 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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Processed Meteorites

• 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 primitive meteorite
Primitive
Stony primitive meteorite
Differential iron meteorite
Differential stony meteorite
Processed
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Origin of Meteorites

• Carbon rich meteorites came from the outer
  portion of the asteroid belt. (gt 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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Comets

• Icy Planetesimals that have been left over from
  the formation of the Solar System.

Sun Grazing comet observed by The Solar and
Heliospheric Observatory (SOHO).
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Anatomy of a Comet
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Comets exist as bare nuclei over most of their
orbits and grow a coma and tails only when they
approach the Sun
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The Kuiper Belt and the Oort Cloud
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Pluto

• 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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Cosmic Collisions

• 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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Comet Shoemaker-Levy 9
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Comet Shoemaker-Levy 9
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The End.
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Comet Shoemaker-Levy 9

• Was shatter by Jupiters gravity in 1992.
• All pieces hit Jupiter in the summer of 1994
  leaving dark impact scars.

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Images obtained by Dan Bruton in 1994
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Meteor Shower
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Minor Body Comparisons
Property ___Asteroids
_________ Comets
Orbit Shape Circular to Highly
elliptical elliptical
Size 0.5 km to 625 km Nucleus 1 to 10
km
Composition Iron or Rocky Ice and Rock
Named? Named by their Named after
their discoverers discoverers
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Earth Impacts and Near Misses

• Arizona Meteor Crater
• measures 1 mile across
• from an impact 50,000 years ago
• by a 50 meter meteoroid

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• Tunguska Event
• in 1908
• an asteroid broke up in our atmosphere
• leveled trees for some 30 kilometers

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Frequency of Impacts versus impactor size
Effects
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• Chicxulub Event /cheek-shoo-loob/
• 65,000,000 years ago
• 10 kilometer asteroid
• is thought to have caused a mass extinction of
  dinosaurs

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The End...
Live long and prosper.