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| Titel |
Analysis of Spitzer IRS Observations of Uranus: Implications for Temperature Structure, Composition and a Standard Calibration Model for Herschel |
| VerfasserIn |
G. Orton, L. Fletcher, A. Mainzer, C. Merlet, D. Hines, H. Hammel, M. Burgdorf, J. Moses |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250022056
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| Zusammenfassung |
| The Spitzer Infrared Spectrometer (IRS) was used to observe the disk of Uranus on 17
December 2007, shortly following its equinox. The low-resolution (R~90) spectral modes of
the IRS covered wavelengths between 5 and 21.5 μm, and its high-resolution (R~600) modes
covered wavelengths between 10 and 36.5 μm. Spectral features arising from methane,
ethane, acetylene, diacetylene and methylacetylene are easily detectable. Sufficient coverage
of the spectrum which is dominated by the opacity provided by the collision-induced
absorption of molecular hydrogen allowed disk-averaged temperatures to be determined
between 100 and 600 mbar pressure. An upward extension of this coverage to the lower
stratosphere was facilitated by matching discrete hydrogen quadrupole S(1) and S(2) lines,
which also provided constraints on the stratospheric para- vs ortho-H2 ratio. These
constraints were merged with those at lower pressures derived from Voyager-2
occultation experiments. Regular and deuterated methane absorption and emission are
consistent with vapor-pressure-limited mixing of methane in the stratosphere, an
upper-tropospheric abundance which is 40% of its fully saturated value, and a D/H ratio
consistent with one derived from earlier measurements by ISO. Observations of the
disk-averaged spectrum over different longitudes imply substantial spatial variability of
stratospheric temperatures at pressures below 1 mbar, but no variability above the
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