37th DPS Meeting, 4-9 September 2005
Session 67 Laboratory Research
Oral, Friday, September 9, 2005, 2:00-3:30pm, Law LG19

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[67.06] New Laboratory Measurements of the Microwave Absorption of Ammonia under Jovian Conditions

T. R. Hanley, P. G. Steffes (Georgia Institute of Technology)

Current retrievals of the abundance of ammonia in the outer planets from microwave brightness temperature measurements and radio occultation studies are reliant upon a number of various models for ammonia opacity, each only valid at certain temperatures, pressures, and frequencies. Using these models can result in uncertainties in the retrieved abundances by up to 20/% at wavelengths near 1.0 cm (Gibson et al., 2005). Particularly important wavelengths are 1.1 cm and those longward of above 6 cm, where the current models are lacking supporting laboratory data. The longer wavelengths are especially important as their weighting functions peak deeper in the Jovian atmosphere, well below the ammonia and water vapor cloud layers. New laboratory data are presented of the measured microwave opacity of a 2.032 + 0.04 /% ammonia (NH3), 92.338 /% hydrogen (H2), and 5.63 /% helium (He) gas mixture at 293 K in the pressure range from 1 to 6 bars. Additional new laboratory measurements of a 0.996 + 0.02 /% NH3, 85.409 /% H2, and 13.595 /% He mixture at 293 K and 205 K from 1 to 6 bars and 180 K from 0.5 to 1 bar at wavelengths from 1.1 cm to 20 cm will also be presented. The data are compared to estimates from current models to resolve which model is most accurate under each set of conditions. These results, plus future measurements conducted under the higher pressures and temperatures characteristic of the deep atmospheres of the outer planets will be of direct application to missions such as Juno, which will map the Jovian microwave emission from 1.3 to 50 cm.

This work was supported by the NASA Planetary Atmospheres Program under the Grant NAG5-12122.

The author(s) of this abstract have provided an email address for comments about the abstract: gtg237n@mail.gatech.edu

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.