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Abstract
The abundances of ices in planetary environments are obtained through measurements of near-infrared absorption features ([special characters omitted]=10,000-4,000 cm−1, λ=1-2.5 μm), and near-IR measurements of materials present in the interstellar medium are increasingly common. In the studies presented here, the near-IR band strengths for molecules are determined through correlations to their better-known mid-IR characteristics. These strengths are used to determine the column densities of molecules in interstellar dense clouds or other environments from observed data. The first set of experiments focused on the near-IR features of molecules relevant to the study of interstellar icy grain mantles and planetary bodies: CO, CO 2, C3O2, CH4, H2O, CH 3OH, and NH3. The spectra of these species were studied in the near-IR region from 10,000-4,000 cm−1 and in the mid-IR region from 4,000-400 cm−1 after the slow growth of films at ∼5K. The results were then used the results to determine the near-IR band strengths of each molecule. Many icy satellites have surfaces that are dominated by either N2 or H2O, and ices in the ISM are primarily composed of H2O. The second set of experiments is focused on the near-IR absorption features of CO, CO 2, CH4, and NH3 diluted in H2O and diluted in N2. Since the compositions of icy planetary bodies and interstellar ices are affected by processing due to UV light and proton bombardment, spectra of UV photolyzed and proton irradiated ices of N2 + CO 2 and H2O + CO2 have been collected to determine the extent of energetic processing on icy bodies in the outer solar system. These studies have shown that planetary ices are best represented by laboratory analogs comprised of mixed, energetically processed ices.
