Abstract EANA2024-78

 

With exploration and sample collection of rock from Mars’ surface well underway by NASA’s Perseverance rover, the NASA-ESA Mars Sample Return (MSR) campaign presents new avenues of analysis in astrobiology. As such, previously limited analysis of sample lithology will be paired with high-resolution, high-sensitivity instrumentation in order to view and analyze microstructures and nanostructures, such as mineralogical composition, rock texture, and potentially astrobiologically significant contents, which can collectively aid in understanding paleoecology and taphonomy. Organo-sedimentary structures, such as stromatolites, provide an analogue for studying potential biosignatures present within the samples from Mars due to some parallels between the geological contexts of the Precambrian on Earth and the Noachian and early Hesperian on Mars. The roles of sediment and geochemical cycling within stromatolites, thus, may be of interest in the understanding of symbiotic, self-sustaining microbial communities in the evolution of life (Lapôtre et al., 2022).                                                    

Four stromatolite samples from the Congo craton have been imaged using two complementary techniques, X-ray µCT and neutron tomography, in which X-ray µCT is optimal for high-resolution reconstructions of density-distinct phases, while neutron tomography is optimal for lower resolution scans, allowing for the characterization of the distribution of light element-dominated phases. Here we aim to reconstruct, segment, and interpret datasets obtained using these two techniques, alongside optical microscopy and TEM imaging in thin sections and chemical data, to identify stromatolite microstructures, phase relationships, and pathways of organic preservation that may serve as analogues for the analysis and interpretation of geological materials brought to Earth from Mars by Mars Sample Return. The correlation of these imaging techniques applied to known organo-sedimentary structures determined their potential use in the characterization of future samples. Furthermore, while the application of X-ray CT to the analysis of stromatolites has been demonstrated (Hickman-Lewis et al., 2017), the use of neutron tomography has yet to be explored in the study of organo-sedimentary material.

Synchrotron technologies are proposed for further exploration of organo sedimentary samples, as a multi-technique, cross-disciplinary approach using varying technologies can exceed the limitations presented by standard laboratory techniques (both destructive and non-destructive) within the geosciences and astrobiology. Synchrotron technologies can offer far superior resolution and detail at the nanoscales at which microfossils and pseudo-microfossil-like-structures are present. As such, establishing a baseline for the reliability and validity in known, terrestrial organo-sedimentary samples is crucial in determining how best to apply synchrotron technologies to rare samples, kept at high containment, which will be which will be brought to Earth from Mars.

 

References                                                                                                                                                                                                     1.Hickman-Lewis, K., Garwood, R.J., Withers, P.J., Wacey, D. (2017). X-ray microtomography as a tool for investigating the petrological context of Precambrian cellular remains. In A.T. Brasier, D. McIlroy and N. McLoughlin (Eds.), Earth system evolution and early life: A celebration of the work of Martin Brasier (pp.33-56). Geological Society of London Special Publication.

2.Lapôtre, M. G. A., Bishop, J. L., Ielpi, A., Lowe, D.R., Siebach,K. L., Sleep, N. H., Tikoo, S.M. (2022). Mars as a time machine to Precambrian Earth. Journal of the Geological Society, 179(5).