Abiotic versus biotic iron mineral transformation studied by a miniaturized backscattering Mössbauer spectrometer (MIMOS II), X-ray diffraction and Raman spectroscopy

Abstract

Searching for biomarkers or signatures of microbial transformations of minerals is a critical aspect for determining how life evolved on Earth, and whether or not life may have existed in other planets, including Mars. In order to solve such questions, several missions to Mars have sought to determine the geochemistry and mineralogy on the Martian surface. This research includes the two miniaturized Mössbauer spectrometers (MIMOS II) on board the Mars Exploration Rovers Spirit and Opportunity, which have detected a variety of iron minerals on Mars, including magnetite (Fe 2+Fe3+2O4) and goethite (α-FeO(OH)). On Earth, both minerals can derive from microbiological activity (e.g. through dissimilatory iron reduction of ferrihydrite by Fe(III)-reducing bacteria). Here we used a lab based MIMOS II to characterize the mineral products of biogenic transformations of ferrihydrite to magnetite by the Fe(III)-reducing bacteria Geobacter sulfurreducens. In combination with Raman spectroscopy and X-ray diffraction (XRD), we observed the formation of magnetite, goethite and siderite. We compared the material produced by biogenic transformations to abiotic samples in order to distinguish abiotic and biotic iron minerals by techniques that are or will be available onboard Martian based laboratories. The results showed the possibility to distinguish the abiotic and biotic origin of the minerals. Mossbauer was able to distinguish the biotic/abiotic magnetite with the interpretation of the geological context (Fe content mineral assemblages and accompanying minerals) and the estimation of the particle size in a non-destructive way. The Raman was able to confirm the biotic/abiotic principal peaks of the magnetite, as well as the organic principal vibration bands attributed to the bacteria. Finally, the XRD confirmed the particle size and mineralogy

Laboratory Analysis of Returned Samples from the AMADEE-18 Mars Analog Mission

“…The technique is well suited for in situ analyses of rocks and minerals, and has been used for mineral identification and organic detection of the target sample (Ferraris et al, 2012;Edwards et al, 2013). Raman spectroscopy has been proposed as a method for geological identification of Marsrelated materials, and will be used during the future martian missions SuperCam and Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) (NASA Mars 2020) or the European Space Agency's (ESA)-Raman Laser Spectrometer System (Exo-Mars) (Beegle et al, 2015;Wiens et al, 2016;Rull et al, 2017).…”

“…Identification of mineral species is achieved by using the RRUFF Database within the Crystal Sleuth software (Laetsch and Downs, 2006;Downs et al, 2015). The following references for each mineral were considered alongside the spectral analyses: oxides (Balachandran and Eror, 1982;Wang et al, 2004;Markovski et al, 2017), carbonates (Rull-Perez and Martinez-Frias, 2003;Buzgar and Apopei, 2009), pyroxenes (Huang et al, 2000;Wang et al, 2001), feldspar (Freeman et al, 2008;Lalla et al, 2015Lalla et al, , 2019, clays (Apopei and Buzgar, 2010;Lalla et al, 2016;Black and Hynek, 2018), and organics (Ferrari, 2007). The organics present in the main Raman bands in the range of 2800 to 3000 cm -1 correspond to C-H bonding, and the other less intense bands *1300 cm -1 correspond to C-C vibrations (Beegle et al, 2015).…”

57Fe Mössbauer, XRD, FT-IR, FE SEM Analyses of Natural Goethite, Hematite and Siderite

“…[31][32][33][34][35] After landing the Mössbauer instrumentation along with other spectroscopic and imaging techniques on the Mars surface the presence of goethite and jarosite minerals was detected. This can be taken as strong evidence of water presence in far history of Mars.…”

Investigation of Raman Spectroscopy (with Fiber Optic Probe) and Chemometric Data Analysis for the Determination of Mineral Content in Aqueous Infant Formula

“…For trace element determination, RS can provide sophisticated spectral information of chemical composition with high resolution [30]. It has also been used to determine minerals on planetary surfaces [31,32], in bones, [33] and oil paintings [34]. Recently, RS combined with chemometrics has been reported to determine Ca content in chicken bone and meat mixtures (R 2 CV of 0.775 with RMSECV of 0.33%) [35] and to predict Ca content in powdered infant formula accurately (R 2 CV of 0.954 with RMSECV of 0.490 mg/g) [36].…”