| Abstrakt: |
Siliceous hot spring deposits, or sinters, deposit from hot spring discharge at Earth's surface and are sites of exceptional preservation of biosignatures. Their macro‐ and micro‐textures are regarded as important evidence of past microbial activities in hydrothermal environments. However, biology mimics do occur, and bona fide microbial textures could be destroyed by subsequent diagenesis or other post‐depositional processes. Thus, it is paramount to narrow the search for prospective Martian silica‐rich deposits that may contain biosignatures from both orbital and rover‐based perspectives. This study investigates hydrothermal deposits in Chile, which are analogs of high‐silica deposits discovered in the Gusev crater on Mars, through remote sensing and laboratory analysis. Results indicate that compositional remote sensing based on multispectral data with a high spatial resolution of <4 m/pixel reflects various concentrations of silica, which assisted in identifying the direction of discharged hydrothermal flows from the vent to the apron. Micro‐infrared mapping of sinters from similar hydrothermal fields linked spectral features to specific textures revealed by scanning electron microscope and chemical compositions confirmed by electron microprobe analysis, indicating that sinters with no shift in their emissivity minimum in the thermal infrared range were more likely to preserve cellular structures. An instrument for collecting multispectral data with higher spatial resolution could aid in characterizing the geologic settings of potential hot springs on Mars. Locating emissivity minima in the infrared regions of silica that do not shift to a lower position would suggest the potential for well‐preserved microbial structures in Martian sinters, if life ever did exist there. Plain Language Summary: Macro‐ and micro‐textures of silica sinters formed in hot springs on Earth are valuable records of microbial activities. Nevertheless, alteration by subsequent processes, some non‐biological, may produce biological mimics. Therefore, identifying sinters with potential biogenic textures is crucial in selecting silica‐rich astrobiological targets. Here, we report orbital‐scale surveying and micro‐scale surveys of silica deposits in Chile, which are comparable to an inferred hydrothermal environment in Gusev Crater on Mars, where the Spirit rover found high‐silica deposits with similar textures. Remote sensing analyses of the El Tatio region provided contextual information regarding silica distribution and its relationship to land surface temperatures and biogenic pigments in the active geothermal area. High‐resolution multispectral data were particularly useful in identifying the flow direction of discharging thermal waters. Detailed spectral and chemical analyses of Chilean sinters suggest that no shift in the position of the minimum feature in the mid‐infrared spectra relates to sinters containing well‐preserved biological textures. This spectral characteristic indicates no substitution of Al for Si, which in turn suggests less likelihood of subsequent processes causing damage to the sinter textures. This study holds promise for identifying future astrobiological targets on Mars from orbital data and onsite spectroscopy. Key Points: High‐resolution multispectral data are helpful in determining the vent‐to‐distal apron geological setting of a hydrothermal siteThe shift of emissivity minima to a lower position in the thermal infrared range may suggest the substitution of Al for Si in silicaHigh‐resolution orbital data and hyperspectral rover‐scale infrared data can aid the search for biosignatures in hydrothermal areas on Mars [ABSTRACT FROM AUTHOR] |
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