HR: 15:10h
AN: P13G-03    [Abstracts]
TI: Surface Binding Energies Of N₂, CH₄, And H₂O-ice Systems
AU: Mastrapa, R M
EM: rmastrapa@arc.nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000,
AU: * Cadarette, T
EM: tcadaret@ScrippsCollege.edu
AF: Scripps College, 1030 Columbia Ave, Claremont, CA 91711,
AU: Sandford, S A
EM: ssandford@arc.nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000,
AB: We will present measurements of binding energies of the following systems: CH₄-CH₄, CH₄- H₂O, N₂-N₂, and N₂-H₂O determined from measurements made in a cryo-vacuum system following the methods of Sandford and Allamandola (1, 2). Briefly, for the N₂-N₂ and CH₄-CH₄ measurements, we monitored the area of relevant infrared features with time at three different temperatures (<50 K) and use the results to estimate sublimation rates. For the mixtures H₂O/CH₄ = 20 and H₂O/N₂= 20, we carried out a series of experiments in which we deposited the mixtures at increasingly higher temperatures (starting at 15 K) until the infrared features of the more volatile component are no longer seen (usually at > 50 K). We then use the deposition rate of H₂O to estimate the residence time of the more volatile species (N₂ or CH₄). In previous measurements (3), binding energies of several volatile molecules (CO, CO₂, H₂) to H₂O-ice were found to be considerably higher than the binding energies of these molecules to themselves. For example, the binding energy of CO on CO is ΔHs/k = 960 K, while that of CO on H₂O is ΔHs/k = 1740 K. These results have implications for the condensation, residence time, and sublimation of volatile species on icy surfaces inside and outside of the Solar System. 1. S. A. Sandford, L. Allamandola, Icarus 87 (1990). 2. S. A. Sandford, L. Allamandola, Icarus 76, 201 (1998). 3. S. A. Sandford, L. J. Allamandola, Astrophysical Journal 417, 815 (1993).
DE: 5422 Ices
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting