Adsorption of water on JSC-1A (Simulated moon dust samples) - A surface science study

Abstract

JSC-1a (a simulated lunar dust sample) supported on a silica wafer (SiO2/Si(111)) has been characterized by scanning electron microscopy (SEM), energy dispersive x-ray (EDX)spectroscopy, and Auger electron spectroscopy(AES). The adsorption kinetics of water has been studied primarily by thermal desorption spectroscopy (TDS) and in addition by collecting isothermal adsorption transients. Blind experiments on the silica support have been performed as well. JSC-1 a consists mostly of aluminosilicate glass and other minerals containing Fe, Na, Ca, and Mg, as characterized in detail in prior studies, for example, at NASA. The particle sizes span the range from a few micrometers up to 100 μm. At small exposures, H2O TDS is characterized by broad (100-450) K structures; at large exposures, distinct TDS peaks emerge, which are assigned to amorphous solid water (ASW) (145 K) and crystalline ice (CI) (165 K). Water dissociates on JSC-1a at small exposures but not on the bare silica support. Coadsorption TDS data (alkane-water mixtures) indicate that rather porous condensed ice layers form at large exposures, with the mineral particles acting most likely as nucleation sites. At thermal impact energies, the initial adsorption probability amounts to 0.92 ± 0.05. It is evident that the drop-and-dry technique, developed in studies about nanoparticles/tubes, can be extended to obtain samples for surface science studies based on powders consisting of particles with rather large diameters. Copyright © 2008 John Wiley & Sons, Ltd.