Lecture_10

# Lecture_10 - Remnants of Rock and Ice Mid-term 1 Results...

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1 Remnants of Rock and Ice Remnants of Rock and Ice Asteroids, Comets, and Pluto Mid-term 1: Results • Number of questions = 40 • Average score = 36.46 or 91.2% (A-) • Median score = 38 or 95% (A) • Maximum score = 40 or 100% • Minimum score = 19 or 47.5% • Well done! This is very good but remember, things get harder from now on. Keep up with your reading and take the homework very seriously. Remnants of Rock and Ice: Remnants of Rock and Ice: Asteroids and Meteorites Asteroids and Meteorites Our Goals for Learning • Why is there an asteroid belt? • How are meteorites related to asteroids? Asteroid Asteroid Facts Facts • Asteroids are rocky leftovers of planet formation. • Largest is Ceres , diameter ~1,000 km • 150,000 in catalogs, and probably over a million with diameter >1 km. • Small asteroids are more common than large asteroids. • All the asteroids in the solar system wouldn’t add up to even a small terrestrial planet.

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2 Asteroids are cratered and not round Eros Ida and Dactyl More than 150,000 asteroids at their predicted locations for Jan 1 2004 On this scale, asteroids are much smaller than the dots used to represent them Why are there very few asteroids beyond Jupiter’s orbit? A. There was no rocky material beyond Jupiter’s orbit. B. The heaviest rocks sank towards the center of the solar system. C. Ice could form in the outer solar system. D. A passing star probably stripped away all of those asteroids, even if they were there at one time. Which explanation seems to be the most plausible? A. The belt is where all the asteroids happened to form. B. The belt is the remnant of a large terrestrial planet that used to be between Mars and Jupiter. C. The belt is where all the asteroids happened to survive. But WHY didn’t they form a little planet?
3 Gravitational interactions (orbital resonances ) with Jupiter have ejected asteroids on certain orbits producing “gaps” and prevented all the asteroids from forming a larger object. Rocky planetesimals survived in the asteroid belt between Mars and Jupiter because they did not accrete into a planet. Jupiter’s gravity, through the influence of orbital resonances, stirred up asteroid orbits and thereby prevented their accretion into a planet. How are meteorites related to asteroids? Meteorites are pieces of asteroids - or sometimes planets or the Moon. Meteor: The bright tail of hot debris from the rock as it burns up due to friction with Earth’s atmosphere. Also called A “shooting star” – but has nothing to do with stars! Meteorite:

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Lecture_10 - Remnants of Rock and Ice Mid-term 1 Results...

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