Orbit-Dependent Spectral Trends for the Near-Earth Asteroid Population

Hdl Handle:
http://hdl.handle.net/10150/195785
Title:
Orbit-Dependent Spectral Trends for the Near-Earth Asteroid Population
Author:
Fevig, Ronald Adrey
Issue Date:
2006
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Results of visible to near-infrared spectrophotometric observations of 55 near-Earth asteroids (NEAs) are reported. The observing techniques, instrumentation, and method of data analysis are described. A new asteroid classification method that directly compares these NEA spectra with spectral features of meteorites is presented. Two major siliceous groups (having discernible "1-micron" absorptions) result from this method, OC-likes which match the spectra of ordinary chondrites and S-types. The dataset shows a preponderance of spectra consistent with ordinary chondrites (23 NEAs), as well as S-types (19), 2 with spectra consistent with black ordinary chondrites, 2 R-types, and 9 that show no 1-micron absorption.The spectral characteristics of the siliceous S-type and OC-like asteroids blend together, providing evidence that S-type asteroids are simply ordinary chondrites whose surface has been modified by weathering. This helps resolve the long standing question of the lack of main belt asteroids having spectra matching ordinary chondrite meteorites. Main belt asteroids have on average much older surfaces while NEAs that exhibit OC-like spectra have younger surfaces.It was found that fresh objects having spectra consistent with ordinary chondrites (1) occupy mostly highly eccentric Apollo orbits which encounter a strong collisional environment in the asteroid main-belt, (2) may have been recently injected into high eccentricity orbits, or (3) have suffered tidal disruption. S-type NEAs reside primarily in orbits that do not cross the asteroid main-belt. This orbit dependent trend is verified by using the larger NEA dataset of Binzel et al. (2004a).Nine NEAs from this survey exhibiting no 1-micron absorption can be associated with extinct comets, iron meteorites or enstatite meteorites. It is shown that most of these NEAs must be extinct comets, implying a considerably larger fraction of comets among the NEA population than previously thought. A correlation of these objects with low inclination orbits is found.This study finds that the NEA population is divided roughly as follows: ~40% fresh ordinary chondrites, ~35% S-types, ~20% extinct comet candidates, and ~5% in minor classes. This work may guide NEA mitigation planning should such an emergency arise.
Type:
text; Electronic Dissertation
Keywords:
Planetary Sciences
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Planetary Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Fink, Uwe
Committee Chair:
Fink, Uwe

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleOrbit-Dependent Spectral Trends for the Near-Earth Asteroid Populationen_US
dc.creatorFevig, Ronald Adreyen_US
dc.contributor.authorFevig, Ronald Adreyen_US
dc.date.issued2006en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractResults of visible to near-infrared spectrophotometric observations of 55 near-Earth asteroids (NEAs) are reported. The observing techniques, instrumentation, and method of data analysis are described. A new asteroid classification method that directly compares these NEA spectra with spectral features of meteorites is presented. Two major siliceous groups (having discernible "1-micron" absorptions) result from this method, OC-likes which match the spectra of ordinary chondrites and S-types. The dataset shows a preponderance of spectra consistent with ordinary chondrites (23 NEAs), as well as S-types (19), 2 with spectra consistent with black ordinary chondrites, 2 R-types, and 9 that show no 1-micron absorption.The spectral characteristics of the siliceous S-type and OC-like asteroids blend together, providing evidence that S-type asteroids are simply ordinary chondrites whose surface has been modified by weathering. This helps resolve the long standing question of the lack of main belt asteroids having spectra matching ordinary chondrite meteorites. Main belt asteroids have on average much older surfaces while NEAs that exhibit OC-like spectra have younger surfaces.It was found that fresh objects having spectra consistent with ordinary chondrites (1) occupy mostly highly eccentric Apollo orbits which encounter a strong collisional environment in the asteroid main-belt, (2) may have been recently injected into high eccentricity orbits, or (3) have suffered tidal disruption. S-type NEAs reside primarily in orbits that do not cross the asteroid main-belt. This orbit dependent trend is verified by using the larger NEA dataset of Binzel et al. (2004a).Nine NEAs from this survey exhibiting no 1-micron absorption can be associated with extinct comets, iron meteorites or enstatite meteorites. It is shown that most of these NEAs must be extinct comets, implying a considerably larger fraction of comets among the NEA population than previously thought. A correlation of these objects with low inclination orbits is found.This study finds that the NEA population is divided roughly as follows: ~40% fresh ordinary chondrites, ~35% S-types, ~20% extinct comet candidates, and ~5% in minor classes. This work may guide NEA mitigation planning should such an emergency arise.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectPlanetary Sciencesen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorFink, Uween_US
dc.contributor.chairFink, Uween_US
dc.contributor.committeememberLauretta, Danteen_US
dc.contributor.committeememberBrown, Roberten_US
dc.contributor.committeememberSwindle, Timothyen_US
dc.contributor.committeememberGehrels, Tomen_US
dc.identifier.proquest1977en_US
dc.identifier.oclc659746551en_US
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