Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p21b1217e&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P21B-1217
Physics
[5422] Planetary Sciences: Solid Surface Planets / Ices, [6045] Planetary Sciences: Comets And Small Bodies / Physics And Chemistry Of Materials
Scientific paper
The coexistence of solid methane and water ice has been observed in outer Solar System objects, in comets, and in interstellar ice mantles (1-3). CH4 is proposed to be the starting point of rich organic chemistry in the astrophysical media. This work presents an investigation on ice mixtures of methane and water, studied by infrared spectroscopy, following some previous results of our group (4). The spectra provide evidence of a distorted CH4 structure, characterized by an absorption band at 2900 cm-1, forbidden by symmetry in the pure solid, already observed by Hodyss et al (5). We present an estimation of the amount of distorted CH4 trapped in the water ice structure and its dependence on the ice generation procedure. The presence of methane clusters inside the sample directly affects the frequency and intensity of the dangling bonds of water. When CH4 is deposited on water ices, the adsorption process follows a Type I isotherm graphic, indicating the microporous nature of the ices. We have also determined the CH4:H2O desorption energy. References (1) Boogert, A.C.A. “Interstellar Ices”. Astrophysics of Dust, ASP Conference Series, Vol. 309, p. 547, 2004. A.N. Witt, G.C. Clayton. (2) Voss, L.F. et al., “Methane thermodynamics in nanoporous ice: A new methane reservoir on Titan.” J. Geophys. Res., 112, E05002, doi: 10.1029/2006JE002768, 2007. (3) Öberg, K.I. et al., “The c2d Spitzer Spectroscopic Survey of ices around low-mass stellar objects. III. CH4.” ApJ, 678, 1032-1041, 2008. (4) Gálvez, O. et al., “Spectroscopic effects in CH4/H2O ices”, Ap. J., in press. (5) Hodyss, R. et al, “Photochemistry of methane-water ices”, Icarus 200, 338, 2009.
Escribano R. M.
Gálvez O.
Herrero Víctor J.
Maté Belén
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