Probing asteroid composition using visible and near-infrared spectroscopy.

Hdl Handle:
http://hdl.handle.net/10150/187372
Title:
Probing asteroid composition using visible and near-infrared spectroscopy.
Author:
Howell, Ellen Susanna.
Issue Date:
1995
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:
The compositional distribution of asteroids provides clues to understanding solar system formation and evolutionary processes in the asteroid belt. The surface mineralogy and distribution of volatiles on asteroids is determined using visible and near-infrared spectroscopy. A revised asteroid taxonomy is developed which incorporates compositional information from the near-infrared asteroid spectra. A search is conducted for organic compounds on distant asteroids, thought to be most volatile-rich in composition. Our near-infrared spectroscopy of outer belt asteroids shows a trend of increasing red continuum slope with heliocentric distance. I interpret this trend as a compositional change, possibly due to increasing abundance of complex organic compounds on these more distant objects. I do not observe a CN absorption band near 2.2 $\mu$m, and conclude that the organics present are not primarily CN-bearing solids. The 3-$\mu$m water absorption band is not detected on distant D asteroids, but is seen on main belt D asteroids. This observation is consistent with the idea that D asteroids are volatile-rich, but the object must be heated in order to transform the silicates into hydrated minerals. No evidence of clay minerals is seen on any of the distant asteroids observed. The majority of the Jupiter Trojan asteroids have a uniform spectral appearance in spite of collisional processing, which implies that the dark red surface material is not a thin surface coating, but is representative of the bulk composition. Observations of near-Earth asteroids indicates a wide range of compositions, suggesting a variety of source regions. Two objects are detected which may contain hydrated minerals, a valuable resource in space. Three near-Earth asteroids are studied in detail, revealing a range of pyroxene chemistry and olivine content inconsistent with ordinary chondrite composition. The occurrence of spectral variability, and implied compositional inhomogeneity is approximately 20%, and on spatial scales as small as tens of meters. This observation implies that asteroids are geologically complex, not chemically uniform, as is often assumed in meteorite studies.
Type:
text; Dissertation-Reproduction (electronic)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Planetary Sciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Lebofsky, Larry
Committee Chair:
Lebofsky, Larry

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleProbing asteroid composition using visible and near-infrared spectroscopy.en_US
dc.creatorHowell, Ellen Susanna.en_US
dc.contributor.authorHowell, Ellen Susanna.en_US
dc.date.issued1995en_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.abstractThe compositional distribution of asteroids provides clues to understanding solar system formation and evolutionary processes in the asteroid belt. The surface mineralogy and distribution of volatiles on asteroids is determined using visible and near-infrared spectroscopy. A revised asteroid taxonomy is developed which incorporates compositional information from the near-infrared asteroid spectra. A search is conducted for organic compounds on distant asteroids, thought to be most volatile-rich in composition. Our near-infrared spectroscopy of outer belt asteroids shows a trend of increasing red continuum slope with heliocentric distance. I interpret this trend as a compositional change, possibly due to increasing abundance of complex organic compounds on these more distant objects. I do not observe a CN absorption band near 2.2 $\mu$m, and conclude that the organics present are not primarily CN-bearing solids. The 3-$\mu$m water absorption band is not detected on distant D asteroids, but is seen on main belt D asteroids. This observation is consistent with the idea that D asteroids are volatile-rich, but the object must be heated in order to transform the silicates into hydrated minerals. No evidence of clay minerals is seen on any of the distant asteroids observed. The majority of the Jupiter Trojan asteroids have a uniform spectral appearance in spite of collisional processing, which implies that the dark red surface material is not a thin surface coating, but is representative of the bulk composition. Observations of near-Earth asteroids indicates a wide range of compositions, suggesting a variety of source regions. Two objects are detected which may contain hydrated minerals, a valuable resource in space. Three near-Earth asteroids are studied in detail, revealing a range of pyroxene chemistry and olivine content inconsistent with ordinary chondrite composition. The occurrence of spectral variability, and implied compositional inhomogeneity is approximately 20%, and on spatial scales as small as tens of meters. This observation implies that asteroids are geologically complex, not chemically uniform, as is often assumed in meteorite studies.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorLebofsky, Larryen_US
dc.contributor.chairLebofsky, Larryen_US
dc.contributor.committeememberLewis, John S.en_US
dc.identifier.proquest9620428en_US
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