Asteroids

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Asteroids

• Levi Houston
• Jason Zastrow

temporaldoorway.com/.../image/gaspra.jpg
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History

• January 1, 1801 Giuseppe Piazzi
• Irregularly shaped-cratered worlds
• Over next six years-3 more
• Pallas
• Vesta
• Juno

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Characteristics

• 16 larger than 240 km
• Ceres-largest, 1000 km
• Ceres mass is 25 of the combined mass of all
  other asteroids
• Total of all asteroids 1500 km less than ½
  diameter of our moon
• Mathildes Density is not much greater than water
  not solid object but rather compacted pile of
  debris (Doppler affect-radio waves)

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Theories

• Old theory, broke up planet destroyed by a
  massive collision
• Current theory, debris left over from failed
  planet formation _at_ 2.8 AU from sun

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Formation

• Rocky fragments left over from formation of solar
  system 4.6 billion years ago
• Planets did not form due to gravitational pull
  being too weak

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Asteroid Classifications

• C-Type 75 - extremely dark, similar to
  carbonaceous chondrite meteorites
• S-Type 17 - Relatively bright, metallic
  nickel-iron mixed with iron and magnesium
  silicates
• M-Type 5-8 even brighter, pure nickel-iron
• Dozens of other types

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Location

• Main Belt- between Mars and Jupiter
• 2 4 AU from Sun
• Follow elliptical path-same direction as planets
• Could be captured by gravitational pull of
  planets then considered a moon
• Main Belt divided into subgroups, named after the
  main asteroids in each group

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http//filer.case.edu/sjr16/asteroid.html
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Near Earth Asteroids

• Everyday about one hundred tons of interplanetary
  material finds its way to the Earths surface
• Near Earth Asteroids (NEAs.)
• are comets and asteroids that have been nudged by
  the gravitational attraction of nearby planets
  into orbits that allow them to enter the Earth's
  neighborhood

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NEA Example

• Manicouagan Reservoir
• This impact is unique because it is one of the
  largest craters on Earth
• 70 kilometer diameter crater has been eroded by
  glaciers

mapy.pomocnik.com/img/wiki600px-STS009_Manico
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NEAs cont

• Scientists are unsure of the number of collisions
  impacted on planet Earth
• This is due to the vastness of our oceans and how
  older craters are buried deep in the crust of the
  Earth
• Chicxulub crater
• May be responsible for the extinctions that took
  place at the end of the Cretaceous period 65
  million years ago

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Chicxulub

www.psi.edu/hartmann/pic-cat/images332_chixulub ww
w.igeofcu.unam.mx/chicxulub/pic/meteor.gif www.imp
erial.ac.uk/pictures/buildings/crater1.jpg
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Barringer Meteor Crater

• Winslow, Arizona

laps.fri.uni-lj.si/duke/HPpictures/crater.jpg
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www.jcphome.com/images/arizona/DSC00056.JPG
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More Classifications

• Main concentration-Kirkwood gaps relatively
  empty regions between groups
• Trojans-located near Jupiters Lagrange points
• Centaurs
• 2060 Chiron between Saturn and Uranus
• 5335 Damocles from Mars to beyond Uranus
• 5145 Pholus from Saturn to past Neptune

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Missions to Asteroids

• Galileo
• NEAR Shoemaker
• Deep Space 1
• Stardust
• Dawn

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Galileo

• 1991
• 1st mission to explore asteroid close-up
• Flew by asteroids Gaspra Ida
• Asteroids were irregularly shaped
• Found fractures craters

http//www2.jpl.nasa.gov/galileo/sepo/cruise/gaspr
a/hires.html
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Galileo

• 243 Ida-moon
• Dactyl
• Diameter 1.5km
• Orbits 100 km from Idas center
• Possibly a fragment

http//www2.jpl.nasa.gov/galileo/sepo/cruise/ida/i
da.html
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NEAR Shoemaker(Near-Earth Asteroid Rendezvous)

• February1996
• numerous asteroid flybys
• 1st to orbit land on surface of asteroid
• 1997 flew by asteroid 253 Mathilde
• High resolution images

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NEAR Shoemaker

• 2000 orbited 433 Eros for 1 year
• Studied magnetic field, mass, orbit, composition
  surface
• 2001 1st controlled descent to surface of Eros
• Images data

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Deep Space 1

• 1998
• Test confirm new technology
• 1999 flew by asteroid 9969 Braille to within 16
  miles
• Similarities between Braille Vesta

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Stardust

• 1999
• Goal tests for later missions
• Flew by asteroid Annefrank to within about 2,000
  miles
• Cratered, irregularly shaped 8 km in diameter

www.astronews.com
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Future Mission - Dawn

• 2007
• Study Ceres Vesta over 9 year period
• Robotic exploration
• 1st to orbit two asteroids on a single expedition

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Dawn Mission

• Initially June of 2006
• Terminated - technical problems and cost
• Later reinstated, but increased in cost from 373
  to 446 million

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Questions?