Abstract EANA2026-55

Microbial mats preserved in the 3.2 Ga Moodies Group from the Barberton greenstone belt in South Africa are the earliest direct evidence of terrestrial life on Earth and their elucidation—in terms of metabolism, taphonomy and astrobiological relevance—is therefore scientifically important for life detection in ancient geological materials. Using a range of techniques, we are studying core samples containing microbial mats (from the ICDP BASE project) throughout the Moodies Group . Using FTIR spectroscopy, we have shown that fossil microbial mats contain large amounts of well-preserved syngenetic organic matter, preserved as biofilms in a chert matrix. MicroCT and nanoCT imaging has enabled us to locate promising regions of interest for thin sections through these mats, which will be used to obtain detailed understanding of their preserved organic microstructures. We will present our µCT and nanoCT analyses, focusing on what these datasets tell us about the petrological context and preserved micromorphologies of the mats. A next step is to measure total organic carbon to see how these organics are concentrated in the mats and to see what remains in the oxidised areas of the samples. Hydropyrolysis will reveal the organic composition of the mats, which we know from FTIR measurements are not entirely aromatic carbon. We can then use SEM, (DUV) Raman, micro-FTIR, O-PTIR and LA ICP-MS to investigate the in situ chemical and structural makeup of the mats and so possibly identify the structure and types of microbes that formed these mats as well as their mode of metabolism. These analyses will be essential to constrain the types of ecosystems that may be responsible for forming these microbial mats.

 

The Moodies Group  provides a pertinent analogue for ancient sequences of siliciclastic sedimentary rocks on Mars, in which similar organic materials may be preserved. Siliciclastics at both Jezero crater and Oxia Planum are proposed as sequences with high biosignature preservation potential. Studying the nature and distribution of organic materials in the Moodies Group can therefore provide a framework for identifying and characterising organics in similar environments on Mars.