CARBON ABUNDANCE AND SILICATE MINERALOGY OF ANHYDROUS INTERPLANETARY DUST PARTICLES

We have studied nineteen anhydrous chondritic interplanetary dust part icles (IDPs) using analytical electron microscopy. We have determined a method for quantitative light element EDX analysis of small particle s and have applied these techniques to a group of IDPs. Our results sh ow that some IDPs have significantly higher bulk carbon abundances tha n do carbonaceous chondrites. We have also identified a relationship b etween carbon abundance and silicate mineralogy in our set of anhydrou s IDPs. In general, these particles are dominated by pyroxene, olivine , or a subequal mixture of olivine and pyroxene. The pyroxene-dominate d IDPs have a higher carbon abundance than those dominated by olivines . Members of the mixed mineralogy IDPs can be grouped with either the pyroxene- or olivine-dominated particles based on their carbon abundan ce. The high carbon, pyroxene-dominated particles have primitive miner alogies and bulk compositions which show strong similarities to cometa ry dust particles. We believe that the lower carbon, olivine-dominated IDPs are probably derived from asteroids. Based on carbon abundances, the mixed-mineralogy group represents particles derived from either c omets or asteroids. We believe that the high carbon, pyroxene-rich anh ydrous IDPs are the best candidates for cometary dust.