Investigation of Carbonaceous Phases in Interplanetary Dust Particles by Acid Dissolution of Microtomed Thin-Sections

Abstract

Interplanetary dust particles (IDPs) collected from the stratosphere are grains of cosmic dust delivered from asteroids and comets. IDPs are composed of complex mixtures of carbon, silicate glass and submicron to nanometer-sized minerals including Fe-Mg silicates, Fe-Ni sulfides, oxides and metal. Bulk SEM and detailed TEM investigations of stratospheric IDPs in the size range of 5 - 15 μm have shown that many IDPs have remarkably high concentrations of carbon - essentially the highest carbon abundances of any known extraterrestrial materials - and often this carbon is intermixed at the nanometer scale with other constituent phases. in order to investigate the properties, occurrence and spatial distribution of carbon in IDPs, we have developed a unique aciddissolution technique using standard microtomed thin-sections to remove the silicate and oxide fractions, thereby leaving a residue primarily of carbon and Fe-Ni sulfides. This technique causes no damage to the delicate microtomed sections or TEM grid and dramatically minimizes the quantity of acids required for etching.