A CRITICAL EXAMINIANTION OF RELATIVE CONCENTRATIONS OF VOLUME-CORRELATED AND SURFACE-CORRELATED SUBMICRON GLOBULES OF PURE Fe IN LUNAR SOILS

Introduction: Impacts on lunar soils produce melt and vapor in an approximate proportion of 7:1 [1]. The melt scavenges soil grains of diverse size, quenches and forms agglutinates, thereby converting surface correlated components of soil grains as volume correlated components; simultaneously, parts of the vapor may condense or escape. Cumulative small impacts increase the maturity of the soils, increase the abundance of agglutinates, and increase the concentration of vapor condensated material. Since the discovery of vapor deposited crystalline Fe 0 in vugs of regolith breccias [2] and the theoretical anticipation of amorphous vapor deposits of diverse composition coating lunar soils grains [3], empirical evidence is gathering in support of such deposits [4-6], now commonly called 'vapor deposited patina' (VDP). In addition, submicron globules of Fe 0 are seen to be ubiquitous in VDP [7, 8]. The amorphous VDP lowers the albedo of lunar soils, affects magnetic properties of soils [9, 10] , changes the slopes of uv-vis-ir reflectance spectra [11-13], and potentially also alters the gamma and x-ray spectra of lunar soils, compromising compositional inferences from remote sensing. Motivation: Recently, it was argued that VDP presently hosts the majority of Fe 0 in lunar soils, e.g., " Past dogma had it that the majority of the nanophase Fe 0 resides in the agglutinitic glasses. … surface-bonded nanophase Fe 0 is present mainly as vapor-deposited patinas on the surfaces of almost every particle of mature soils … " [9]. Because of these and similar conclusions, it is important to reevaluate the relative contribution of volume-correlated nanophase Fe 0 and surface-correlated nanophase Fe 0 ; we have undertaken this project and report our preliminary results here. Background: Literature data show that relative to non-agglutinate grains individual agglutinates have higher I S /FeO (a measure of superparamagnetic Fe 0); agglutinates are more magnetic; solar wind element concentrations are higher in agglutinates; inverse correlation with grain size is not unique for SCC – systematic increase of a component in the finer fractions would also show the same relationship; and, most soil grains, especially in the finer fractions, are broken from regolith breccias and recycling agglutinates; these grains have coatings of glassy breccia matrix and agglutinitic glass. [14-21]. In short, in mature soils, VCC overwhelms SCC although the origin of the components may be surface-related, e.g., in VDP. Note also that the volume of VDP on grain surfaces is far less than the volume of …