Establishing a molecular understanding of isotopic enrichment and variation in extraterrestrial organic solids contained within Chondritic meteorites

Dr. George Cody

Thursday, September 29, 2022 - 11:00
General Seminar (Hybrid)
Dr. George Cody, Earth and Planets Laboratory

Carbonaceous Chondrite meteorites are derived from some of the most primitive (least altered) and earliest (youngest) planetary objects in the Solar System. Chondrites are notable in that they contain a relatively large amount of organic carbon (~ 2 wt %) in the form of a complex insoluble organic macromolecule (referred to as IOM). Nearly 60 years ago it was shown that the IOM has substantial enrichments in deuterium (relative to terrestrial D/H values) which points to some connection with cold (possibly interstellar) chemistry capable of producing some enrichment. Extensive solid state Nuclear Magnetic Resonance (NMR) experiments have revealed that the molecular structure of IOM varies considerably across various chondritic meteorites where such molecular evolution arises from parent body processing during radiogenic heating of the parent planetesimal. However, no systematic relationship between D/H nor 13 C/ 12 C and the degree of molecular evolution is observed for IOM from many chondrites. We have applied D and 1 H NMR (at natural abundance) to IOM samples from two different chondritic meteorites. D NMR enables us to see directly where D resides in IOM at the molecular level. Laboratory experiments on the synthesis of IOM using 1 H, D, and 13 C NMR point to deuterium enrichment arising at the time of IOM synthesis, where the source of deuterium is derived from the water IOM is synthesized in. Combining this insight with a detailed molecular analysis of molecular evolution and D/H variation exhibited in IOM from the Tagish Lake clasts enables us to resolve the combined effects of molecular evolution on variation in IOM’s D/H abundances. If time permits, we will also present evidence for a potential molecular origin for 13 C/ 12 C variation in IOM across chondritic meteorites.