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M. J. Wolff, R. T. Clancy (Space Science Institute), K. M. Pitman (Louisiana State University)
The presence of water ice-dust composite particles in the Martian atmosphere has been periodically suggested (e.g., Colburn, D. S. et al., 1989, Icarus, 79, 159; Michelangeli, D. V. et al., 1993, Icarus, 100, 261). While the theoretical motivation for this type of particle is quite plausible, observational evidence has typically been limited to anecdotal cases, i.e., AM-PM lander opacity differences. The data returned from the Mars Global Surveyor Thermal Emission Spectrometer (TES) offers the first real opportunity to quantify both the presence and the microphysical nature of such water ice-dust aerosols. In this presentation, we will compare and contrast the effects of composite particles with those of separate populations of pure water ice and dust. This will be accomplished through a combination of theoretical scattering calculations (T-matrix, discrete dipole, coated sphere) and radiative transfer model-data comparisons. The latter will involve primarily TES emission phase function sequences (both visible bolometer and thermal spectral data).
Our work has been supported through NASA (MDAP) grant NAG5-9820 and (MED) JPL contract 961471.