Fourier transform infrared spectroscopy is an efficient technique for the detection and quantification of molecules in gas mixtures. Measurement results from a mobile laboratory for ambient air analysis and for remote sensing of plume emission with the commercially available K300 spectrometer are reported. CO, CO(2), NO, NO(2), N(2)O, NH(3), CH(4), SO(2), H(2)O, HCl, and HCHO concentrations have been determined with good agreement with in situ results. The on-line multicomponent analysis software is based on line-by-line retrieval and least-squares fitting procedures, including the effects of multiple aerosol scattering and cloud and rain influences.
One central problem in understanding the Martian upper atmosphere is the poor correlation between exospheric temperatures and the energy input from the Sun in the EUV and UV. Turbulence heats the atmosphere by dissipation of turbulent energy and cools it by downward heat transport. A time-variable turbulence may introduce a stochastic component in addition to the solar-driven, regular variation of the exospheric temperatures. To investigate the possible range of temperatures on the basis of this assumption, we developed a one-dimensional mean-dayside model of the energy balance of the Martian upper atmosphere. With plausible assumptions on the range of the eddy diffusion coefficient, we find a stochastic component of + 63 K for the exospheric temperatures. The comparison of observed data with the results of our model yields a best value for the efficiency of the heating by absorption of solar ultraviolet radiation of 0.145 + 0.05. INTRODUCTION In the years from 1965 to 1976, eleven spacecraft missions to Mars have been carried out which yielded information about the Martian upper atmosphere (here, z > 120 km). The majority of the data consist of measurements of plasma density height profiles and of intensity profiles of various airglow features such as the CO Cameron and Ly • emissions. From these, upper atmosphere temperatures have been inferred, even though exclusively for the dayside [Hunten, 1968; Anderson and Hord, 1971; Stewart, 1972; Stewart et al., 1972; Kliore et al., 1972, 1973;Stewart and Hogan, 1973; Lindal et al., 1979]. Except for the Mariner 6 and 7 Ly • data [Anderson and Hord, 1971], the measured scale heights refer to the altitude region from 150 to 200 km. Most authors understand them as topside scale heights' i.e., corresponding temperatures are exospheric or, strictly speaking, exobase temperatures. The exobase at Mars, however, is at about 250 km. Different from the region near the exobase, the thermosphere between 150 and 200 km is not necessarily isothermal. Hence local scale height measurements are required in that region for the derivation of reliable temperatures. The measurements, however, have an insufficient height resolution' all temperatures as inferred from the scale height measurements are height-averaged thermospheric temperatures rather than local or exospheric ones. A second problem is to what extent the measured scale height of the specific feature reflects the neutral atmosphere scale height or temperature. For the emission scale heights, the connection seems to be evident. However, for the plasma scale heights, simple functional relations like H e = 2H, exist only for a Chapman layer type ionosphere or a diffusive/thermal equilibrium ionosphere where, additionally, the ion composition must be known. These conditions are only partially met in the Martian upper atmosphere. If we disregard the dependence of the temperatures on the solar zenith angle, we estimate that the total systematic error in the quoted exospheric temperatures, especially those derived from plasma scale he...
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