Nanophase Fe0 in lunar soils

Back scattered electron and transmission electron imaging of lunar soil grains reveal an abundance of submicrometer-sized pure Fe-0 globules that occur in the rinds of many soil grains and in the submillimeter sized vesicular glass-demented grains called agglutinates. Grain rinds are amorphous silicates that were deposited on grains exposed at the lunar surface from transient vapors produced by hypervelocity micrometeorite impacts. Fe-0 may have dissociated from Fe-compounds in a high temperature (> 3000 degrees C) vapor phase and then condensed as globules on grain surfaces. The agglutinitic glass is a quenched product of silicate melts, also produced by micrometeorite impacts on lunar soils. Reduction by solar wind hydrogen in agglutinitic melts may have produced immiscible droplets that solidified as globules. The exact mechanism of formation of such Fe-0 globules in lunar soils remains unresolved.