Abstract/Details

Titan's upper atmospheric structure derived from Voyager ultraviolet spectrometer observations


1997 1997

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Abstract (summary)

The Voyager 1 Ultraviolet Spectrometer (UVS) observations are the only direct measurements we have of Titan’s upper atmosphere. Previous analysis of the two UVS solar occultations yielded densities for N2 CH4 and C2 as well as the thermospheric temperature. These results serve as the upper atmospheric boundary conditions in models of Titan’s atmosphere; however, there are discrepancies between the observations and models, and the previous analysis itself is known to be internally inconsistent.

We have undertaken a reanalysis of the UVS solar occultations to resolve these differences and to extract the maximum amount of information from the data. In so doing, we have developed a detailed model of the UVS detector and a new analysis method tailored to retrieving multiple species from an occultation of a finite-sized source such as the sun.

Our analysis has yielded density profiles for nine species in Titan’s upper atmosphere and a new measurement of the thermospheric temperature. We find higher N2 densities and lower CH4 and C2 densities than those previously determined. We also find a thermospheric temperature of 150-155 K instead of 176-196 K as in the early analysis. Densities for C2 HCN, and HC3N are retrieved for the first time.

Titan’s atmosphere is one of the most interesting in the solar system. The composition and high degree of photochemical activity elicit comparisons to the early terrestrial atmosphere and considerations about the origins of life. Our results provide improved and expanded constraints for the atmospheric models and should provide scientists with a better view of Titan’s upper atmosphere, which is important in planning for the upcoming Cassini mission.

Indexing (details)


Subject
Astronomy;
Astrophysics;
Atmosphere
Classification
0606: Astronomy
0606: Astrophysics
0608: Atmosphere
Identifier / keyword
Pure sciences; Saturn
Title
Titan's upper atmospheric structure derived from Voyager ultraviolet spectrometer observations
Author
Vervack, Ronald Joe, Jr.
Number of pages
305
Publication year
1997
Degree date
1997
School code
0009
Source
DAI-B 58/08, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780591570038, 0591570033
Advisor
Sandel, Bill R.
University/institution
The University of Arizona
University location
United States -- Arizona
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9806816
ProQuest document ID
304331090
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304331090/fulltextPDF
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