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LifeSpringsMARS

Exploring the Internal Textures and Physical Properties of Digitate Sinter in Hot Springs: Implications for Remote Sampling on Mars

Nersezova, E. E.; Rowe, M. C.; Campbell, K. A.; Ang, A.; Matthews, S.; Ruff, S. W.; Meghwal, A.; Adam, L.; Galligan, N.; Loho, T. Exploring the Internal Textures and Physical Properties of Digitate Sinter in Hot Springs: Implications for Remote Sampling on Mars. Planetary and Space Science 2023, 238, 105786. https://doi.org/10.1016/j.pss.2023.105786.

MicroCT results showing microbial and abiotic porosity within digitate sinter. Comparison between a polarised light microscopic image (A, C) and corresponding microCT scan slice (B, D) of the exposed digitate sinter surface, with the associated 2D porosity of slices along the Z axis for Te Kopia (A-B) and El Tatio (C-D). Relative density positively correlates with microCT intensity; purple areas represent lower densities, and yellow/orange areas represent higher densities.

Read the abstract here:

Hydrothermal silica deposits on the surface of Mars with textures analogous to terrestrial hot spring deposits are, arguably, one of the best potential targets in the search for evidence of life beyond Earth. Here we investigate terrestrial hot spring digitate silica structures (modern: El Tatio, Chile; Mars Pool at Rotokawa geothermal area, and Te Kopia thermal stream, New Zealand; 1.6–1.8 ka: Opal Mound, Utah, U.S.A.), which are texturally and mineralogically analogous to martian deposits in the Columbia Hills of Gusev crater, in order to elucidate how their physical properties vary with depositional environment, and to help guide future remote sampling endeavors. Micro-computed tomography allows visualization of the internal texture of geological materials through variations in porosity and relative density, and is demonstrated here as a key, non-invasive technique for investigating future returned planetary samples. Bulk porosity, associated with pore sizes greater than >1–2 μm, varies from 4.7 to 21.3% in the four studied terrestrial digitate sinter samples, representing a range of fluid pHs of formation. Moreover, density variations between laminae largely reflect a nano-scale porosity (6 GPa (Opal Mound). Regions of nano-porous silica in all samples reduces the hardness in these areas to <1 GPa. No significant variation in material properties can be correlated to different fluid chemistries of the modern samples. Collectively, these results imply that the preservation of silicified microbes in digitate sinter structures should lead to a decrease in material hardness and elastic modulus owing to higher porosity in microbial laminae, whereas recrystallization of opal-A or secondary fluid precipitation will lead to hardening. For future remote sampling on Mars, the range of material properties of siliceous materials must be considered when designing appropriate sampling devices, as martian materials both harder and softer than accounted for in the design process may create sampling challenges.​

 

Access at: https://www.sciencedirect.com/science/article/pii/S0032063323001551

MicroCT results showing microbial and abiotic porosity within digitate sinter.
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