| Autor: |
Terry Herter, Bruce Pirger, George E. Gull, Gordon L. Bjoraker, Susan R. Stolovy |
| Rok vydání: |
1996 |
| Předmět: |
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| Zdroj: |
Icarus. 121:411-421 |
| ISSN: |
0019-1035 |
| DOI: |
10.1006/icar.1996.0096 |
| Popis: |
We observed Jupiter on 17–19 July 1994 using NASA's Kuiper Airborne Observatory (KAO) deployed out of Melbourne, Australia. The KAO Echelle Grating Spectrograph (KEGS) uses an array detector with 128 spectral elements and 20 spatial elements. The spectral resolution was 0.19 cm −1 , equivalent to a resolving power of 6800. We detected three H 2 O emission lines near 7.7 μm as well as numerous emission features of CH 4 . At the peak of the fallback phase for the ejecta from the G and K fragments, we infer temperatures between 1000 and 1200 K at the 3-μbar pressure level on Jupiter. The H 2 O lines at 7.7 μm were visible for only about 10 to 20 min. We obtained line-of-sight abundances of H 2 O for both G and K of 1.0 to 1.5 × 10 18 cm −2 . The inferred mass of H 2 O in each fragment ranges from 1.4 to 2.8 × 10 12 g, equivalent to spheres of ice 140 to 180 m in diameter at unit density. This should be considered a lower limit to H 2 O as the 7.7-μm data are sensitive only to the hottest component of water. The G and K impact sites exhibited remarkably similar spectra at the time of peak infrared emission about 14 min after impact. The inferred abundance of H 2 O at this time was comparable to that of CH 4 . We interpret the observed CH 4 emission as due to heating of pre-existing jovian CH 4 in the upper stratosphere. Water in the impact sites can be explained by shock chemistry provided that the C/O ratio is less than 1. Our observations are consistent with a scenario in which oxygen-rich cometary material combines with jovian H 2 to produce H 2 O during the fallback phase. Combining our observations with spectra acquired from the Near Infrared Mapping Spectrometer on the Galileo spacecraft, we do not believe that the fragments reached the 6-bar level in order to excavate jovian water. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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