Condensed Lecture Notes 1-9

Condensed Lecture Notes 1-9 - GEO 303 CONDENSED LECTURE...

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GEO 303 CONDENSED LECTURE NOTES 1-9 Fall 2010 1 Comment: terms below that are printed in boldface are meant to catch your attention, and you will note that most of them are nouns. In science nouns are necessary, but verbs—the processes of the earth—are more important and these will be emphasized in Quiz 1. The quiz will be a mixture of very easy, to a few quite challenging questions. The more difficult questions will ask you to take something you already know and put the pieces of information together to come up with a conclusion. LECTURE 1: ORIGIN OF THE SOLAR SYSTEM Our sun is one of about 200 billion stars in the Milky Way galaxy. Based on a number of lines of evidence, we believe the sun and its solar system, including Earth, to have originated about 4.5 billion years ago. From telescope observations we infer that the majority of star formation takes place in nebulae, clouds of gas and dust in space. Over time clouds with sufficient density slowly collapse, with clumps of matter shrinking under the influence of their own gravity . This process is aided by photoevaporation , in which light and particles from nearby stars hit individual particles in the cloud, accelerating them inward. Eventually larger clumps separate into smaller ones, and one of these may eventually condense into a spinning, bulging solar disk , the center of which becomes a star and the outer material possibly becoming a series of planets. Meteorites provide us with a lot of information about the history of our solar system. There are many different types of meteorites. Some contain clumps of the very first matter to condense, but never joined the sun or a planet and thus stayed pristine for over 4 billion years. Other meteorites are from small planetoids that began to form but then were destroyed during early, violent collisions; these give us snapshots of what happens deep inside a planetary body, much deeper than we can dig or drill here on Earth. Others are blasted-off pieces of other planets. Eventually the matter in our solar system condensed into the arrangement of planets and other bodies we see today. Based on the physics of a rotating disk of dust we would expect the inner planets to be larger and denser than the outer ones, but we find that this is only partially the case. The inner planets (Mercury, Venus, Earth, and Mars) are small but dense, containing rock and metal but relatively little volatile (gaseous or liquid) material. Beyond the inner planets lies the asteroid belt , a zone of dispersed rocky material without enough mass to create a planet of its own. The outer planets (Jupiter, Saturn, Uranus and Neptune) are much larger gas giants , consisting largely of light atoms and molecules (hydrogen, helium, methane, ammonia) in their gaseous or liquid form, though possibly with rocky cores. We postulate that when the sun condensed enough to start the fusion reaction that provides its energy, the early, violent solar wind drove volatiles away from the inner planets, a closer-to-home
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Condensed Lecture Notes 1-9 - GEO 303 CONDENSED LECTURE...

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