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CHEM 222 (20)
Chapter 5

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CHEM 222
Karine Auclair

The Present Solar System Our Solar System at present… - 9 planets (all but two have moons) - A belt of 6000-10000 asteroids mostly between Mars and Jupiter - Kuiper Belt – 200 million comets spreading from Pluto to 20x Sun’s distance - Oort Cloud – Several billion comets 5.1 Collisions with Comets and Asteroids? 5.1.1 Comets - Most comets come from the Kuiper Belt, and sometimes from the Oort Cloud - Comets enter the inner solar system in elliptical (almost parabolic) orbits - Speeds as high as 80 000km/hr - Halley’s Comet – trapped within the Solar System • Aphelion (farthest distance from Sun) – as far as Pluto • Perihelion (closest distance to Sun) – as close as Venus 5.1.2 Asteroids - Most are gathered in the orbital ring beyond Mars - Biggest asteroid = Ceres, then Pallas, Juno, Vesta, Eugenia, Siwa, Kleopatra The Chicxulub Impact Event - 64.98 million years ago - A large asteroid (10km diameter?) struck Earth at Chicxulub, Mexico • Caused an 180km diameter crater - The atmosphere was filled with dust • Solar insolation was blocked – Earth became very cold • Dinosaurs starved to extinction - When the dust clouds settled, CO from v2pourized rocks remained and the greenhouse shielding heated up the Earth to very high temperatures - Asteroidal Winter became a Greenhouse Summer - Only Darwinian winners survived - Another such event occurred about 35 million years ago Comet in Russia - Trees were laid down radially, and the impact was heard 1000km away, but there is no evidence that any materials reached the ground at impact centre. - The high velocity of a comet (higher than asteroids because comets have fallen in from greater distances) causes its explosion in the upper atmosphere. - The effects on the surface were caused by an atmospheric shock wave from the explosion of the comet 5.2 What are Comets, Meteoroids, and Asteroids? Comets - Sometimes display bright, long tails - Records of returns of periodic comets has provided us with some of the best evidence for the known dynamics of the Earth’s and Moon’s orbits and rotations. - Comets are the primordial material from which our Solar System condensed. • “Dirty snowballs” – water, methane ice, dusts, gases - When their orbits bring them close to the sun, the ice vapourizes • This releases dust and gases, which are carried away from the comet in a direction out from the Sun by a high-speed solar wind Asteroids and Meteoroids - Metallic or rocky debris which clutter the Solar System Asteroid - Most asteroids are organized into a near-circula
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