20-EPN2-108: Ultrastructure and nano-geochemistry of organic materials in 3.4-billion-year-old stromatolites

20-EPN2-108: Ultrastructure and nano-geochemistry of organic materials in 3.4-billion-year-old stromatolites: windows into biogeochemical cycling on the early Earth (and Noachian Mars?)

Visit by Keyron Hickman-Lewis to TA2 Facility 29 – Nano Secondary Ion Mass Spectrometer (South Korea) and TA2 Facility 34 – Atomic Level Electronic Structure STEM (South Korea).
Dates of visit: 12-24 June 2022

Report Summary: This TA visit used the facilities of the Korea Basic Science Institute at Daejeon (analytical transmission electron microscopy) and Busan (nano-scale secondary ion microscopy) to analyses samples of siliciclastic-hosted microbial mats from the Mesoarchaean of Western Australia.

Using NanoSIMS, we performed ion mapping of the bio-essential elements C, N and S, and determined the isotopic fractionations of these elements in order to assess whether preserved elemental cycles reflected abiotic or biotic networks; if biotic, these fractionations can inform us of the type of ecosystem present in the rocks at the time of microbial mat formation. Using analytical TEM, we performed imaging, high-resolution imaging and elemental mapping of ultrathin focussed ion beam-milled sections of microbial mats in order to characterise the ultrastructure of the mats, identify the types of carbonaceous materials present, and determine organic material–mineral relationships at sub-micron resolutions.

The results of the visit will be integrated with datasets obtained at my home institution (e.g. optical microscopy, SEM-EDX and Fourier transform infrared microspectroscopy) to provide a comprehensive analysis of these microbial mats. We will propose analogies between this ancient ecosystem and potential ecosystems in habitable siliciclastic settings on Mars. Overall, the visit was highly successful, during which we analysed more samples than expected and we hope that this will mark the beginning of a longer-term collaboration on the application of nanoscience approaches to planetary science and astrobiology questions.