ABSTRACT
In the upper atmospheres and torus regions of the terrestrial and Jovian planets and in the interstellar medium (ISM), an important mechanism for energy transfer and diagnostic spectroscopy is electron collision processes with both neutral and ionic species leading to the emission of electromagnetic radiation. Six of the planets (Earth, Mars, Jupiter, Saturn, Uranus, and Neptune) are known to have internal magnetic Ÿelds that lead to particle acceleration and energy deposition into a planetary atmosphere (Bagenal et al., 2007). Mercury also has an intrinsic magnetic
28.1 Introduction .......................................................................................................................... 761 28.2UV Spectroscopy of Molecules in Planetary Atmospheres ................................................. 763 28.3Apparatus and Experimental Methods ................................................................................. 767 28.4Present Status of H2, N2, CO, and SO2 ................................................................................. 772
28.4.1H2-UV ...................................................................................................................... 772 28.4.2H2-VOIR ................................................................................................................... 776 28.4.3N2-EUV .................................................................................................................... 780 28.4.4N2-FUV .................................................................................................................... 786 28.4.5CO ............................................................................................................................. 792 28.4.6SO2 ............................................................................................................................ 793
28.5Conclusions ........................................................................................................................... 796 Acknowledgments .......................................................................................................................... 797 References ...................................................................................................................................... 797
Ÿeld with a tenuous atmosphere that is a planetary exosphere. The ubiquitous presence of energetic electron-excited ultraviolet (UV) dayglow and aurora in the solar system (Broadfoot et al., 1979, 1981a,b, 1989; Sandel et al., 1979; Yung et al., 1982; Meier, 1991; Ajello et al., 1998b, 2001, 2005a; Gustin et al., 2002, 2004) has been studied spectroscopically over the last 30 years using observations from interplanetary spacecraft beginning with the Voyager Grand Tour mission and Mars and Venus Mariner missions, and the earth-orbiting satellites beginning with the Orbiting Geophysical Observatories (OGOs) and International Ultraviolet Explorer (IUE). Simultaneously, astronomical observations of H2 Rydberg band emissions from Herbig-Haro and T-Tauri stellar objects (Raymond et al., 1997; Herczeg et al., 2002, 2004; Bergin et al., 2004) and models of H2 Rydberg band emissions generated in the interior of molecular clouds within the ISM (Gredel et al., 1987, 1989; Liu and Dalgarno, 1996) have been achieved, Ÿrst with the Copernicus, which was equipped with a UV telescope (Grewing et al., 1978, Snow, 1979), and followed at higher spectral resolution by the Hubble Space Telescope (HST) with its corrected optics (Petersen and Brandt, 1995).
