Asteroids and Comets
Credit: Emily Lakdawalla |
http://en.wikipedia.org/wiki/File:Comet-Hale-Bopp-29-03-1997_hires_adj.jpg
Monday, November 22, 2010
Class Business
Optional Project is due on Wednesday
Wednesday: Read Chapter 12.3-12.4 [dwarf planets, impacts]
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Asteroids are rocky leftovers from planet formation.
Credit: Emily Lakdawalla
Monday, November 22, 2010
Large asteroids are big enough to be almost spherical.
Monday, November 22, 2010
...but most are irregularly shaped and cratered.
NASA
Monday, November 22, 2010
We can use Newton’s version of
Kepler’s Third Law to measure the
mass of an asteroid.
Monday, November 22, 2010
Some asteroids have unusually
low densities, suggesting that they
are “rubble piles.”
Should the impact that generated the crater above destroyed the asteroid if it was
made of solid rock?
NASA
Monday, November 22, 2010
Other asteroids are higher in density, closer to the value of solid rock.
NASA
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Which explanation for the belt seems the most plausible?
A. The belt is where all of the asteroids happened to form.
B. The belt is a remnant of a large planet that formed between
Mars and Jupiter.
C. The belt is where all of the asteroids happened to survive.
...but why didn’t they form a planet?
Monday, November 22, 2010
Orbital resonances
with Jupiter produce
gaps in the asteroid belt.
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Leftover planetesimals could not accrete because of Jupiter’s
gravitational influence.
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How do we study asteroid composition?
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Most meteorites are fragments of asteroids that have landed on Earth.
http://en.wikipedia.org/wiki/File:Meteorito_Mar%C3%ADlia.jpg
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http://antwrp.gsfc.nasa.gov/apod/image/0808/Perseid_pacholka_750wp.jpg
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http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/image/0903/earthgrazer_ansmet_big.jpg
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http://antwrp.gsfc.nasa.gov/apod/ap091015.html
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Primitive meteorites are largely unchanged from their formation.
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Processed meteorites are thought to be fragments of asteroids that underwent
differentiation.
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Primitive: small flakes/spheres may be the first things that solidified from the solar
nebula
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Processed: evidence for both volcanic activity and metal-rich cores on large asteroids
http://en.wikipedia.org/wiki/File:Seymchan.jpg
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http://en.wikipedia.org/wiki/File:SikhoteAlinMeteorite.jpg
Comets are the icy counterparts to asteroids.
http://antwrp.gsfc.nasa.gov/apod/ap091216.html
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http://en.wikipedia.org/wiki/File:10-1009_comet103p_vcastro-ccsa3.0.jpg
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NASA/JPL/Maryland
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Monday, November 22, 2010
Comet tails always point away from the Sun, regardless of the comet’s motion.
Monday, November 22, 2010