Lect1 Binzel NEOs (09-22-09)

Lect1 Binzel NEOs (09-22-09) - Physical Properties of NEOs...

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Physical Properties of NEOs by Binzel et al.
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OUTLINE 1. Introduction 2. Tabulation of NEO Physical Properties 3. Analysis 1. Taxonomy of NEOs 2. Relationship of NEOs to Comets 3. Relationship of NEOs to Ordinary Chondrites 4. Shapes and Rotations 5. Optical properties and Surface Structure 4. Conclusions and Future Work
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1. Introduction Understanding the source(s) for NEOs is essentially the same as finding the origin locations for meteorites. Hazards, resources, spacecraft targets Purpose of review: physical properties of NEOs and relationships between asteroids, comets, and meteorites.
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1. Introduction Understanding the source(s) for NEOs is essentially the same as finding the origin locations for meteorites. Actually, not quite (explain). Hazards, resources, spacecraft targets Purpose of review: physical properties of NEOs and relationships between asteroids, comets, and meteorites.
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1. Introduction Apollo, Amor and Aten asteroids Why do we know relatively little about objects inside Earth’s orbit?
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2. Tabulation of NEO Physical Properties Table 1. In 2002 about 300 NEOs with at least some physical characterization (now is about three times that number) For most of these, only approximate guesses for albedos and diameters; hence, analyses and conclusions based on albedos and diameters are shaky. Figure 2. What does this alphabet soup mean?
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2. Tabulation of NEO Physical Properties Fig 2
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Major asteroid spectral types (total of 18 recognized types in the Tholen 1984 classification system). Main types are: S: Stony, medium albedo (ordinary chondrites, stony irons) C: Carbonaceous, low albedo (carbaonaceous chondrites) M: Metallic, medium albedo, high radar reflectivity (irons, and other compositions) P and D: Ultra-carbonaceous, very low albedo (possibly one meteorite: Tagish Lake) V: Vesta, high-albedo (basaltic achondrites) E: Enstatite, high-albedo (enstatite achondrites) X: spectra like E, M and P with unknown albedo* U means unclassified * Albedo is most generally defined as percentage of reflected light with respect to incident light. If the albedo is kown, the “X” class can be divided into E, M and P classes. Fig. 2. Why E, M, P AND X? Review of Asteroid Taxonomy
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3. Analysis 1. Taxonomy of NEOs Almost all taxonomic classes of Main-Belt are represented among NEOs. Including P and D- types How significantly is delivery of NEOs dominated by processes that favor inner asteroid belt? S asteroids dominate the sample 4:1. After bias correction (mostly because S-types have higher albedo and lower phase dependence on their albedo) S and C-types are about equal among NEOs
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3. Analysis 1. Taxonomy of NEOs (cont.) Among main belt C-types dominate by as much as 5:1 How significantly is delivery of NEOs dominated by processes that favor inner asteroid belt? Inner belt does dominate , in agreement with dynamical arguments The 3:1 resonance (at 2.5 AU) has roughly equal populations of C- and S-type asteroids in its vicinity, making it a compatible source.
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3. Analysis
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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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Lect1 Binzel NEOs (09-22-09) - Physical Properties of NEOs...

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