37th DPS Meeting, 4-9 September 2005
Session 67 Laboratory Research
Oral, Friday, September 9, 2005, 2:00-3:30pm, Law LG19

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[67.02] Near Infrared spectra of ice mixtures relevant to Solar System ices.

S. A. Sandford, R. M. E. Mastrapa, M. P. Bernstein (NASA Ames Research Center)

We will present near IR spectra of ice mixtures relevant to outer Solar System bodies and review the many differences between spectra of mixtures and those of pure solids. We have found new peaks in mixtures not found in pure spectra. For example, the ``forbidden" CO2 (2"nu"3) overtone near 2.134 microns (4685 cm-1) is present in the spectra of H2O/CO2 = 5 and = 25 mixtures but is absent from that of pure CO2. In both CO2/ H2Oand CH4/ H2O mixtures, we see a feature at 1.89 microns (5290 cm-1) that is likely related to the ``dangling OH" feature at 2.73 microns (3360 cm-1). The two largest near-IR absorptions of CH4 at 2.324 and 2.377 microns (4303 and 4207 cm-1) are at slightly shorter wavelength (higher frequency) and broader when mixed with H2O than in pure solid CH4. The same behavior is seen in CO2/ H2O mixtures. Warming causes some peak positions and profiles in the spectrum of a H2O/ CO2 = 5 mixture to take on the appearance of pure CO2. In CH4/ H2O mixtures the peaks shift to higher frequency and become increasingly broad, but this trend is reversible on re-cooling, even though the phase transitions of H2O are irreversible. We will present estimated absolute strengths for the absorptions of volatiles dissolved in solid H2O. Also, we will discuss results from several other mixtures, including NH3/ H2O, O2/ H2O, and CO2/CH3OH. This work was supported by NASA's Planetary Geology and Geophysics program (NRA-02-OSS-01-PGG).

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Bulletin of the American Astronomical Society, 37 #3
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