Review Exam 2 (10-20-09)

Review Exam 2 (10-20-09) - Review for Exam 2 October 20,...

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Review for Exam 2 October 20, 2009
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Asteroids III Ch. 1 “An Overview of the Asteroids: The Asteroids III Perspective”
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Outline 1. Introduction 2. Brief History of the Primordial Asteroid Belt 3. Present State of Main Belt 4. The Near-Earth-Object Population 5. Predicting the Future
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1. Introduction Two main reasons why we study asteroids Even though asteroids represent only a tiny fraction of the total mass of the terrestrial planets, their large numbers, diverse compositions, and orbital distributions provide powerful constraints for planet formation models. Some of these bodies are capable of striking Earth with enough energy to produce severe or possibly catastrophic damage to our civilization. Main advances since Asteroids II book
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1. Brief History of the Primordial Asteroid Belt 2.1 Formation of Main-Belt asteroids: Linked to planet formation, particularly terrestrial Timescales. Meteorites provide the clock for timing planetesimal formation, e,g., CAIs formed about two million years before chondrules and accretion into asteroids Thermal evolution: Accretion time, e.g., early: more 26 Al, more heat Composition of accreted material, e,g., further out more water Thickness and thermal conductivity of asteroid’s regolith Asteroid’s final diameter e.g., why Vesta differentiated and Ceres did not?
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1. Brief History of the Primordial Asteroid Belt 2.1 Formation of Main-Belt asteroids: why Vesta differentiated and Ceres did not? Possible solution for this frequently-cited main-belt enigma: (4) Vesta, a D = 530 km asteroid in the inner main belt (2.36 AU), has differentiated while (1) Ceres, a much larger D = 930 km asteroid in the central main belt (2.77 AU), apparently has not. It is possible that objects in the inner main belt formed much more quickly than those farther out in the main belt, such that Vesta may have accreted more active 26 Al than Ceres. In addition, the presumed greater availability of volatiles in the outer main belt may have helped inhibit large-scale melting events.
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1. Brief History of the Primordial Asteroid Belt 2.1 Formation of Main-Belt asteroids: why Vesta differentiated and Ceres did not? Possible solution for this frequently-cited main-belt enigma: (4) Vesta, a D = 530 km asteroid in the inner main belt (2.36 AU), has differentiated while (1) Ceres, a much larger D = 930 km asteroid in the central main belt (2.77 AU), apparently has not. It is possible that objects in the inner main belt formed much more quickly than those farther out in the main belt, such that Vesta may have accreted more active 26 Al than Ceres. In addition, the presumed greater availability of volatiles in the outer main belt may have helped inhibit large-scale melting events. Class: Give one example of how volatiles can inhibit melting
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1. Brief History of the Primordial Asteroid Belt 2.2 Dynamical Excitation of Primordial Belt: Large mass depletion: most of the mass was lost, 4 Vesta constrains this mechanism Strong dynamical excitation: originally encounters produced accretion, now they
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This note was uploaded on 11/09/2009 for the course AST 4142 taught by Professor Campins during the Fall '09 term at University of Central Florida.

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Review Exam 2 (10-20-09) - Review for Exam 2 October 20,...

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