ta2.29 – Europlanet

22-EPN3-054: Searching for Biosignatures in Extreme Environments – High-Altitude Andean lakes as Mars analogues

Report Summary: Microbial activity leaves fingerprints in the sedimentary record. Through its metabolism microbes catalyse reactions, thus recycling minerals, dissolved chemical species and gases. This produces changes in the isotopic and trace elements ratios and changes in crystal mineral fabrics, that can be preserved in the sedimentary record. This signals of biological activity, when differentiated from abiotically controlled processes, are known as biosignatures., and are a part of the toolbox of geobiological and astrobiological research. The main question here is how can textural and chemical biogenic signatures be clearly differentiated from abiotically mediated processes? The study of ancient deposits is problematic, in that primary signatures have likely been modified through changes in the chemical environment during diagenetic processes. In contrast, the investigation of modern analogues, where processes can be studied in situ and where secondary alteration is incipient to absent, can help to differentiate between biotically and abiotically controlled signatures in the sedimentary record.

In this study we explored the chemical isotope signature within microbially-related sedimentary carbonates, including: stromatolites, oncoids/pisoids and thrombolites. We focused on carbon isotopes in different microtextures to recognise isotope signatures at the micro-nano-scale with the aim of recognising chemically versus biologically precipitated minerals and organic components.

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.

Back to TA visit reports page.

Back to TA main page.

Back to Europlanet 2024 RI homepage.