Amorphous Silicates and Organic Matter within Cometary Interplanetary Dust Particles – Clues to early Solar Nebula Processes

• Applicant: Dr. Christian Vollmer
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 453960555

During the first million years of Solar Nebula evolution, complex processes such as condensation, accretion, differentiation, or asteroidal modification occurred. Understanding these very first episodes is an important, but challenging task. Most materials that formed during these early stages were subsequently modified or destroyed during Solar System evolution and are therefore not suitable. However, some pristine samples such as carbonaceous chondrites or cometary dust have recorded snapshots of these primary solar nebular events, which can be analyzed by modern techniques on Earth today to disentangle their complex fingerprints. Amorphous silicates and organic matter are specifically important components of chondritic-porous interplanetary dust particles derived from comets. Up to now, only little chemical and physical information is available on the glassy fraction of these grains and the functional chemistry of its organic constituents. There is growing evidence that these two components evolve in response to a variety of processes, possibly in the interstellar medium, the Solar Nebula, and on meteorite/cometary parent bodies, i.e., fractional condensation, ion irradiation, and fluid reactions. The most modern transmission electron microscopes, such as the Themis in Münster or the SuperSTEM microscopes in Daresbury, make it possible to obtain chemical and textural information on these extremely complex materials on a scale not previously accessible. The focus of this proposal is therefore to study the most pristine components within cometary samples, i.e., amorphous silicates and organic matter, with the aim to disentangle very early solar nebular or possibly interstellar processes such as condensation or fluid reactions. Our proposed chemical investigations include both the major element chemistry obtained by STEM-EDX on a nanometer scale as well as the Fe oxidation state of these grains by STEM-EELS. Furthermore, H-C-N isotopic analyses of these IDPs by NanoSIMS will test whether IDP constituents are isotopically anomalous. We will also investigate the functional chemistry and constitution of cometary organic matter by low-dose (60 kV) UltraSTEM EELS investigations. These investigations will help to understand the processes that formed GEMS grains in cometary bodies as well as the molecular constitution of cometary organic matter in comparison with their meteoritic counterparts. If we understand the synthesis and modification of these components, we will also gain a broader understanding of the primitive materials that contributed to larger objects within the Solar System such as comets, asteroids, and rocky planets.

• DFG Programme: Research Grants
• International Connection: United Kingdom
• Co-Investigator: Dr. Jan Leitner
• Cooperation Partner: Professor Dr. Quentin Ramasse