Millimeter/submillimeter Fourier Transform Spectroscopy of Jovian Planet Atmospheres

A new Fourier transform spectrometer, built for use at the Caltech Submillimeter Observatory, has been used to observe all four of the jovian planets (Jupiter, Saturn, Uranus, and Neptune) in the millimeter-submillimeter wavelength range (0.3-3.0 mm). These observations have resulted in the detection of the PH_3 1-0 rotational line (266.9 GHz) in Saturn, and the PH _3 3-2 (800.5 GHz) line in both Jupiter and Saturn. Because PH_3 is a disequilibrium species, it is an important tracer of vertical mixing and upper atmospheric photochemistry, and can therefore be used to derive dynamical and chemical properties of the jovian atmospheres. A jovian planet radiative transfer code has been used to model the observed PH_3 lineshapes. Using the FTS, a spectral line survey covering the entire range of submillimeter frequencies observable from the ground has also been performed on Jupiter at Saturn at a resolution of 200 MHz. This survey has yielded the tentative detection of HCl (and possibly HCN) in Saturn and, again with the aid of radiative transfer modeling, provided a great number of improved upper limits on the concentrations of many other species. Finally, Uranus and Neptune have been observed in the 1300 μm atmospheric window which contains the CO 2-1 transition. This line was not detected in either planet, placing upper limits on the tropospheric CO mole fraction of 0.5 ppm in Uranus and 1.4 ppm in Neptune. A new Fourier transform spectrometer, built for use at the Caltech Submillimeter Observatory, has been used to observe all four of the jovian planets (Jupiter, Saturn, Uranus, and Neptune) in the millimeter-submillimeter wavelength range (0.3-3.0 mm). These observations have resulted in the detection of the PH_3 1-0 rotational line (266.9 GHz) in Saturn, and the PH _3 3-2 (800.5 GHz) line in both Jupiter and Saturn. Because PH_3 is a disequilibrium species, it is an important tracer of vertical mixing and upper atmospheric photochemistry, and can therefore be used to derive dynamical and chemical properties of the jovian atmospheres. A jovian planet radiative transfer code has been used to model the observed PH_3 lineshapes. Using the FTS, a spectral line survey covering the entire range of submillimeter frequencies observable from the ground has also been performed on Jupiter at Saturn at a resolution of 200 MHz. This survey has yielded the tentative detection of HCl (and possibly HCN) in Saturn and, again with the aid of radiative transfer modeling, provided a great number of improved upper limits on the concentrations of many other species. Finally, Uranus and Neptune have been observed in the 1300 μm atmospheric window which contains the CO 2-1 transition. This line was not detected in either planet, placing upper limits on the tropospheric CO mole fraction of 0.5 ppm in Uranus and 1.4 ppm in Neptune.