14_Asteroids - GEL36 SOLAR SYSTEM Lecture 14 Asteroids(Ch...

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1 GEL36 SOLAR SYSTEM Lecture 14: “Asteroids” (Ch. 25) Goal of the Lecture: Asteroids, small rocky bodies that are the last remains of the rocky planetesimals that built the planets 4.6 b.y.a., have had significant influence on Earth through geologic time because of the life-altering and far-reaching environmental effects of collisions between Near-Earth Asteroids and Earth. Dimensions and orbital characteristics asteroids - small rocky bodies that are the rocky remnants of planet building. Asteroids supply the majority of meteorites. ‘Understanding of what and how asteroids are built may not only someday help us deflect or destroy one on a collision course with Earth, but also tell us how Earth was formed. Asteroids preserve within them remnants left over from the debris disk out of which the planets grew some 4.6 billion years ago. Since then, most asteroids have suffered collisions and impacts and often show the scars.’ About 40,000 asteroids are known (some no larger than a house), with countless more undescribed. The vast majority occupy a position 2 to 4 AU from the sun between Mars and Jupiter known as the asteroid belt . These rocky planetesimals orbit in a prograde direction around the sun. - asteroid belt estimated to be about 100 million km thick - asteroids in the belt are spread out with thousands of km between each. All asteroids follow their own orbital path dictated by the gravitational tugs of Jupiter, the inner planets and nearby asteroids. - most asteroids are small, with only 3 larger than 400 km across and only 26 larger than 200 km in diameter - some are spherical, some are irregular potato-shapes, and some are peanut-shaped - millions of asteroids are pea-sized to car-sized and are much more numerous than the big ones - not all asteroids are 4.6 b.y. old - most are much younger because they have had numerous collisions with other asteroids and the ones we see now are remnants of their latest collision.
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2 Visits to asteroids . . . Asteroid Ida
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This note was uploaded on 05/31/2011 for the course GEL 36 taught by Professor Osleger,d during the Spring '08 term at UC Davis.

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14_Asteroids - GEL36 SOLAR SYSTEM Lecture 14 Asteroids(Ch...

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