ADSORPTION OF CH4 ON LABORATORY-MADE CRUSHED ICE AND ON NATURAL SNOW AT 77 K - ATMOSPHERIC IMPLICATIONS

Methane adsorption on crushed ice, annealed crushed ice, and natural s now was measured at 77 K. For surface coverages from 0.05 to 1 monolay er, CH4 adsorption was similar for the 3 types of ice. For surface cov erages of 10(-2) to 10(-5) monolayer, unannealed crushed ice and snow adsorbed CH4 similarly, while annealed crushed ice adsorbed 2 to 3 tim es less CH4. This difference can be due to different densities of surf ace defects such as dangling OH bonds, a small fraction of crystallogr aphic faces with high Miller-Bravais indices, or microcracks. From the se observations, we conclude that further studies of the surface of ic e made using different methods are needed before laboratory adsorption data can be applied to the atmosphere.