Hdl Handle:
http://hdl.handle.net/10150/186927
Title:
Properties of Titan's haze and surface.
Author:
Lemmon, Mark Thomas.
Issue Date:
1994
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:
I have developed a model of aerosol microphysics and scattering in Titan's atmosphere that incorporates the concept of irregular aggregates. By comparing models with spacecraft observations of Titan's intensity and polarization phase laws and ground-based observations of Titan's solar reflection spectrum, I have constrained several properties of the aerosols. The aerosols are assumed to be irregular aggregates of small spheres made of Titan tholin--the spheres have a radius of approximately 0.06 μm, and through most of the atmosphere the aggregates comprise 10 to 100 spheres. The aggregates form at an altitude of 250 to 300 km, and are the primary source of scattering opacity down to the lower stratosphere, where there must be some removal process, such as rain-out, although there is likely to be some scattering opacity in the troposphere. This model fits the polarization data well, in addition to being highly forward scattering. It is used to predict the penetration of sunlight into the atmosphere, and it predicts that the surface becomes visible at wavelengths longer than about 0.9 μm. I then carried out a program of 0.9-2.3 μm spectroscopy of Titan in which Titan's albedo at wavelengths sensitive to the surface was monitored. Results of this program show that Titan's albedo does vary, with the leading hemisphere consistently brighter than the trailing hemisphere, and that the variations repeat with a period equal to Titan's orbital period. The source of the variation is very likely the surface, and there is no evidence of surface absorption features. The amplitude of the light-curve at 2 μm (32 ± 3%) suggests that the bright component is unlikely to have a strong 2 μm absorption feature, and, therefore, is not pure water ice. It is clear from the existence and repetition of the variation that the surface is not homogeneous, and specifically that a global ocean is not allowed.
Type:
text; Dissertation-Reproduction (electronic)
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Planetary Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Tomasko, Martin G.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleProperties of Titan's haze and surface.en_US
dc.creatorLemmon, Mark Thomas.en_US
dc.contributor.authorLemmon, Mark Thomas.en_US
dc.date.issued1994en_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.abstractI have developed a model of aerosol microphysics and scattering in Titan's atmosphere that incorporates the concept of irregular aggregates. By comparing models with spacecraft observations of Titan's intensity and polarization phase laws and ground-based observations of Titan's solar reflection spectrum, I have constrained several properties of the aerosols. The aerosols are assumed to be irregular aggregates of small spheres made of Titan tholin--the spheres have a radius of approximately 0.06 μm, and through most of the atmosphere the aggregates comprise 10 to 100 spheres. The aggregates form at an altitude of 250 to 300 km, and are the primary source of scattering opacity down to the lower stratosphere, where there must be some removal process, such as rain-out, although there is likely to be some scattering opacity in the troposphere. This model fits the polarization data well, in addition to being highly forward scattering. It is used to predict the penetration of sunlight into the atmosphere, and it predicts that the surface becomes visible at wavelengths longer than about 0.9 μm. I then carried out a program of 0.9-2.3 μm spectroscopy of Titan in which Titan's albedo at wavelengths sensitive to the surface was monitored. Results of this program show that Titan's albedo does vary, with the leading hemisphere consistently brighter than the trailing hemisphere, and that the variations repeat with a period equal to Titan's orbital period. The source of the variation is very likely the surface, and there is no evidence of surface absorption features. The amplitude of the light-curve at 2 μm (32 ± 3%) suggests that the bright component is unlikely to have a strong 2 μm absorption feature, and, therefore, is not pure water ice. It is clear from the existence and repetition of the variation that the surface is not homogeneous, and specifically that a global ocean is not allowed.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.chairTomasko, Martin G.en_US
dc.contributor.committeememberLunine, Jonathanen_US
dc.contributor.committeememberHunten, Don M.en_US
dc.contributor.committeememberMelosh, H. Jayen_US
dc.contributor.committeememberChase, Clem G.en_US
dc.identifier.proquest9517541en_US
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