Cross-Scale Multimodal Imaging for Organic Matter in Extraterrestrial Samples.

The analysis of extraterrestrial organic matter in samples returned by space missions provides a unique opportunity to study prebiotic chemistry. A comprehensive understanding of the occurrence and composition of organic matter is fundamental to unraveling its origin and evolutionary history. However, the scarcity and complexity of these materials pose considerable analytical challenges. Here, we developed a cross-scale multimodal imaging workflow that integrated mass spectrometry imaging (MSI) and vibrational spectroscopy imaging, including desorption electrospray ionization coupled quadrupole-time-of-flight mass spectrometry (DESI-Q-TOF/MS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), nanoscale secondary ion mass spectrometry (NanoSIMS), focal plane array-Fourier transform infrared spectroscopy (FPA-FTIR), and optical photothermal infrared spectroscopy (O-PTIR). This workflow was applied to the Murchison meteorite, with the objective of establishing spatial associations between mineral phases, molecular composition, functional groups, and isotopic composition on a scale from the millimeter to the submicron. The spatial resolution of DESI has been improved from 100 to 200 to 20 μm, enabling spatial correlation with other imaging techniques. For the first time, the enrichment of organic matter─including CHN, CHO, and CHNO compounds and polycyclic aromatic hydrocarbons (PAHs)─in fine-grained rims (FGRs) surrounding silicate chondrules has been observed. Furthermore, the cross-scale multimodal imaging also reveals differences in organic matter composition between Ca-carbonate and phyllosilicates, as well as spatial heterogeneity within the latter. This workflow provides a new paradigm for studying the complex occurrence and composition of organic matter in various research fields, enhancing our understanding of prebiotic materials in the solar system.