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I. Phase Transformations and the Spectral Reflectance of Solid Sulfur: Possible Metastable Sulfur Allotropes on Io's Surface. II. Photochemistry and Aerosol Formation in Neptune's Atmosphere

Citation

Moses, Julianne Ives (1991) I. Phase Transformations and the Spectral Reflectance of Solid Sulfur: Possible Metastable Sulfur Allotropes on Io's Surface. II. Photochemistry and Aerosol Formation in Neptune's Atmosphere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/S8F2-V423. https://resolver.caltech.edu/CaltechETD:etd-08012006-093137

Abstract

This thesis consists of two independent papers:

PAPER I:

The spectral reflectance of elemental sulfur is examined in a set of laboratory experiments to determine the factors that affect the transformation rate of monoclinic (β) sulfur and various other sulfur allotropes into orthorhombic (α) sulfur. The laboratory data have implications for the spectral variation and physical behavior of freshly solidified sulfur, if any exists, on Jupiter's satellite Io. Depending on its thermal history, molten sulfur on Io would initially solidify into a glassy solid or a monoclinic crystalline lattice; these forms might contain polymeric sulfur molecules as well as the more abundant S8 molecules. If freshly frozen sulfur on Io could lose heat rapidly and approach ambient dayside Io temperatures within several hours, then some of the metastable sulfur allotropes could be maintained on Io virtually indefinitely. Small droplets of sulfur ejected during plume eruptions might cool quickly enough to preserve these allotropes, but sulfur in large volcanic flows or lakes would probably remain warm long enough for phase transformations to proceed at a visible rate.

PAPER II:

Photodissociation of methane at high levels in Neptune's atmosphere leads to the production of more complex hydrocarbon species such as ethane, acetylene, methylacetylene, propane, diacetylene, ethylacetylene, and butane. These gases diffuse to the lower stratosphere where temperatures are low enough to allow all seven of the aforementioned species to condense. Particle formation may not occur readily, however, as the vapor species become supersaturated. We present a theoretical analysis of particle formation mechanisms at conditions relevant to Neptune's troposphere and stratosphere and show that hydrocarbon nucleation is very inefficient under Neptunian conditions: saturation ratios much greater than unity are required for aerosol formation by either heterogeneous, ion-induced, or homogeneous nucleation. Thus, stratospheric hazes may form far below their saturation levels. We compare nucleation models with detailed atmospheric photochemical models in order to place realistic constraints on the altitude levels at which we expect hydrocarbon hazes or clouds to form on Neptune.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Planetary Science; Geophysics
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Planetary Sciences
Minor Option:Geophysics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Yung, Yuk L. (advisor)
  • Westphal, James A. (co-advisor)
Thesis Committee:
  • Westphal, James A. (chair)
  • Yung, Yuk L.
  • Blake, Geoffrey A.
  • Ingersoll, Andrew P.
  • Burnett, Donald S.
  • Ahrens, Thomas J.
Defense Date:20 May 1991
Additional Information:The thesis title listed in 1991 commencement program -- I. Phase Transformations and the Spectral Reflectance of Solid Sulfur: Possible Metastable Sulfur Allotropes in Io's Surface. II. Photochemistry and Aerosol Formation in Neptune's Atmosphere -- varies from the actual thesis title.
Record Number:CaltechETD:etd-08012006-093137
Persistent URL:https://resolver.caltech.edu/CaltechETD:etd-08012006-093137
DOI:10.7907/S8F2-V423
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/0019-1035(91)90179-wDOIArticle adapted for Paper I.
ORCID:
AuthorORCID
Moses, Julianne Ives0000-0002-8837-0035
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2993
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:18 Aug 2006
Last Modified:08 Nov 2023 00:36

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