Detection and Preservation of Biosignatures in Mars Analogs Hot Spring Deposits from the Taupo Volcanic Zone, New Zealand

Characterizing the preservation potential of biosignatures in martian analogs is essential in the quest for biosignatures with martian rovers. Hot spring silica deposits are part of the minerals with a high preservation potential. As part of an ongoing study, we are characterizing the nature and distribution of organic molecules including lipid biomarkers in a range of analog hot spring deposits, evaluating their preservation potential, and determining the potential signals from flight-like experiments. We are focusing on various geothermal fields in the New Zealand Taupo Volcanic Zone with physical and chemical variabilities. Samples are being extracted for lipid biomarker characterization as well as analysis using flight-like experiments from the current and future pyrolyzer-gas chromatographmass spectrometer instruments SAM and MOMA on the Curiosity and Exomars2020 rovers. The aim of work is to improve our knowledge of the detection and preservation of biosignatures in different hot spring lithologies while simultaneously evaluating the potential limits and biases of flight experiments.Fil: Millan, Maëva. University Of Georgetown; Estados Unidos. National Aeronautics and Space Administration; Estados UnidosFil: Campbell, Kathleen A.. Universidad Nacional y Kapodistriaca de Atenas; GreciaFil: Van Kranendonk, Martin J.. University of New South Wales; AustraliaFil: Sriaporn, Chanenath. Universidad Nacional y Kapodistriaca de Atenas; GreciaFil: Handley, Kim M.. Universidad Nacional y Kapodistriaca de Atenas; GreciaFil: Dobson, Michaela. Universidad Nacional y Kapodistriaca de Atenas; GreciaFil: Camp, Sîan. Universidad Nacional y Kapodistriaca de Atenas; GreciaFil: Teece, Bonnie. University of New South Wales; AustraliaFil: Guido, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Djokic, Tara. University of New South Wales; AustraliaFil: Farmer, Jack D.. Arizona State University; Estados UnidosFil: Stewart Johnson, Sarah. University Of Georgetown; Estados UnidosEPSC-DPS Joint Meeting 2019GenevaSuizaEuropean Process Safety Centr

Assessing the link between Earth’s oldest stromatolites and hydrothermal fluids: The c. 3.5 Ga Dresser Formation, North Pole Dome, Pilbara Craton, Western Australia

Extensive mapping, petrological data and geochemical analyses shed new light on the environment of deposition of cherty sedimentary rocks that contain Earth’s oldest stromatolites in the c. 3.5 Ga Dresser Formation, North Pole Dome, Western Australia. Some researchers have interpreted a quiet shallow water evaporitic setting and others a tidal flat, but detailed stratigraphic and petrographic data supports deposition within a developing volcanic caldera that was flushed by voluminous hydrothermal fluids. A series of stratigraphic profiles measured on either side of the Dresser (barite) Mine over a distance of seven kilometres display true sediment thickness variations across active growth faults, as previously noted. Rapid lateral facies variations and diverse depositional settings, as well as multiple newly discovered eruptive layers of felsic volcaniclastic material support a volcanic caldera setting. Importantly, the first discoveries of geyserite and tourmaline-bearing ferruginous laminates interpreted as radiogenic, B-rich hot spring crusts are documented, providing evidence of emergence of the volcanic landsurface. Geyserite consists of alternating K-Al clay-rich (light) and anatase-rich (dark) laminae, 20 µm thick, that appear identical to modern geyserite formed from alternating acidic and alkaline fluids. Morphologically variable stromatolites, including domical, stratiform and coniform varieties, are restricted to shallow water environments, but are widespread within the lower parts of the succession, suggestive of phototrophs. Spatially more restricted occurrences of dendritic microbialites are overlying large hydrothermal veins, suggestive of chemoautotrophs. The deposition of stromatolitic rocks is inferred to have developed as a response to uplift of the surface during emplacement of a subvolcanic magma system that drove geysers and erupted ash. Subsequent caldera collapse formed deeper basins accompanied by coarse clastic sedimentary rocks in which there are no visible signs of life. Results support a diverse microbial community in these ancient rocks that were able to utilise energy sources from a variety of habitats within stages of a developing volcanic-hydrothermal system

Inferring the age and environmental characteristics of fossil sites using citizen science.

Not all fossil sites preserve microfossils that can be extracted using acid digestion, which may leave knowledge gaps regarding a site's age or environmental characteristics. Here we report on a citizen science approach that was developed to identify microfossils in situ on the surface of sedimentary rocks. Samples were collected from McGraths Flat, a recently discovered Miocene rainforest lake deposit located in central New South Wales, Australia. Composed entirely of iron-oxyhydroxide, McGraths Flat rocks cannot be processed using typical microfossil extraction protocols e.g., acid digestion. Instead, scanning electron microscopy (SEM) was used to automatically acquire 25,200 high-resolution images from the surface of three McGraths Flat samples, covering a total area of 1.85 cm2. The images were published on the citizen science portal DigiVol, through which 271 citizen scientists helped to identify 300 pollen and spores. The microfossil information gained in this study is biostratigraphically relevant and can be used to constrain the environmental characteristics of McGraths Flat. Our findings suggest that automated image acquisition coupled with an evaluation by citizen scientists is an effective method of determining the age and environmental characteristics of fossiliferous rocks that cannot be investigated using traditional methods such as acid digestion

A Reconstructed Subaerial Hot Spring Field in the ∼3.5 Billion-Year-Old Dresser Formation, North Pole Dome, Pilbara Craton, Western Australia

Recent discoveries of geyserite and siliceous sinter with textural biosignatures in the ∼3.5 Ga Dresser Formation of the Pilbara Craton, Western Australia, extended the record of inhabited subaerial hot springs on Earth by ∼3 billion years, back to the time when siliceous sinter deposits are known to have formed on Mars (e.g., at Columbia Hills, Gusev Crater). Here, we present more detailed lithostratigraphic, petrographic and geochemical data collected from 100 measured sections across a ∼14 km strike length in the Dresser Formation. The data indicate deposition of a wide range of hot spring and associated deposits in a restricted interval that directly overlies a hydrothermally influenced volcanic caldera lake facies, with shoreline stromatolites. Hot spring deposits show abrupt lateral facies changes and include associated channelized clastic deposits that support fluvial, subaerial hot spring deposition. All Dresser hot spring and associated lithofacies have direct analogs with proximal, middle, and distal apron hot spring facies that are characteristic of those from New Zealand, Yellowstone National Park, USA, and Argentina. Rare earth element and yttrium geochemistry shows that the Dresser geyserite shares identical patterns with Phanerozoic hot spring sinters. This geochemical data further supports textural and contextual evidence that indicate the Dresser geyserite formed as a subaerial hot spring sinter. Further, the Dresser hot spring deposits are temporally associated with a diverse suite of textural biosignatures that indicate a thriving microbial community existed within in a Paleoarchean hot spring field. The results presented here underscore the importance of continued study of the early geological record for astrobiological research. In particular these findings reinforce the long-standing hypothesis that hydrothermal systems are optimal places to search for past life on Mars.Fil: Djokic, Tara. University of New South Wales; Australia. University of Western Australia; AustraliaFil: Van Kranendonk, Martin J.. University of New South Wales; Australia. Okayama University; JapónFil: Campbell, Kathleen. University of Auckland; Nueva ZelandaFil: Havig, Jeff R.. University of Minnesota; Estados UnidosFil: Walter, Malcolm R.. University of New South Wales; AustraliaFil: Guido, Diego Martin. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Life analog sites for Mars from early Earth: diverse habitats from the Pilbara Craton and Mount Bruce Supergroup, Western Australia

The ancient rocks of the Pilbara region of Western Australia have been an important analog site for the study of possible inhabited environments in the search for life on early Mars for over four decades. Here, we review the evidence for Paleo- to Neoarchean life and the habitats that it occupied in the Pilbara Craton and unconformably overlying Fortescue Group of the Mount Bruce Supergroup. Nine major inhabited environments are described, which range from land to sea, and into the subsurface, showing that life had diversified into, and flourished within, a range of different environments early in Earth history. An important additional component in the search for life on Mars involves the manner in which evidence for early life is preserved. From the examples studied here, early mineralization of organic matter is key to the preservation of reliable biosignatures, in either silica, carbonate, or pyrite, but burial by volcanic ash can also provide excellent preservation

Reasons for no agreement on images.

Venn diagram illustrating the number of times that questions related to specimen count, occurrence, position, name, and image focus on the questionnaire template led to ‘no agreement’ among volunteer citizen scientists. The analysis is based on 275 images that were expert verified as containing pollen or spores (see Fig 3 for details). The top reasons that resulted in ‘no agreement’ included a combination of questions (count, occurrence, position, and name = 78 images), followed by identification of the specimen (75 images). Occurrence—whether or not a microfossil is present in an image; count—number of pollen or spores in an image; position—placement of microfossil on the edge or middle of the image; name—selected from a range of listed specimens; and focus—image is in focus or out of focus.</p

Microfossil identification, counts, and abundance.

(a) The total number of palynomorphs identified across 1.85cm2 of rock surface analysed. Note ‘Spores’ indicates that from ferns and mosses. (b) Pie chart showing the relative abundance (%) of palynomorphs, and in brackets, palynomorph density (number of specimens/cm2).</p

Flow chart outlining the identification and verification steps involved in the analysis of SEM images.

Citizen scientist (volunteers) microfossil identification reduced the SEM image dataset from 25,200 to 4192. Experts reviewed the 4192 images and verified microfossils in 448 images. Accounting for image overlap, the final pollen and spore count in these verified images was 383, of which 300 specimens were identifiable. Key for superscript lettering: a—An ‘agreement’ was reached by a minimum of three volunteers on questions set out in the questionnaire template; this category was then subdivided into images indicated as having ‘no microfossil/s’ and images indicated as having ‘microfossil/s’. b—These images were undisputed (i.e., not disputed by a fourth volunteer). c—These images were disputed by an additional (fourth) volunteer and had to be reviewed by an expert. d—These images were identified by three volunteers as containing other microfossils, that are not pollen or spores. e—If ‘no agreement’ was reached by a minimum of three volunteers on questions set out in the questionnaire template, these images were automatically marked by the system to be reviewed.</p

Location and fossils of McGraths Flat.

(a) Map of Australia depicting the location of McGraths Flat (red star) near the town of Gulgong, Central Tablelands, New South Wales, Australia. (b) Field site. (c) Cross-section of the finely-bedded goethite-rich sedimentary rock from McGraths Flat. (d) Myrtaceous (eucalypt) leaf (AM F.146592). (e) Budding Malvales(?) flowers (AM F.146589). (f) Sawfly (Tenthredinoidea: Symphyta) (AM F.145093). (d-f) modified from McCurry et al., 2022. Note the variation in colour (yellow-red-brown) is dominantly due to grain size, the overall composition is homogeneous. Scale bars, c—1 cm, d—1 cm, e—1 mm, f—2 mm.</p