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Whole microorganisms are rarely preserved in the fossil record but actively silicifying environments like hot springs provide an opportunity for microbial preservation, making silicifying environments critical for the study of microbial life through time on Earth and possibly other planetary bodies. Yet, the changes that biosignatures may undergo through lithification and burial remain unconstrained. At Steep Cone Geyser in Yellowstone National Park, we collected microbial material from (1) the living system across the active outflows, (2) the silicified areas adjacent to flows, and (3) lithified and buried material to assess the preservation of biosignatures and their changes across the lithification transect. Five biofabrics, built predominantly by CyanobacteriaGeitlerinema, Pseudanabaenaceae, and Leptolyngbya with some filamentous anoxygenic phototrophs contributions, were identified and tracked from the living system through the process of silicification/lithification. In the living systems, δ30Si values decrease from +0.13‰ in surficial waters to −2‰ in biomat samples, indicating a kinetic isotope effect potentially induced by increased association with actively growing biofabrics. The fatty acids C16:1 and iso‐C14:0 and the hydrocarbon C17:0 were disentangled from confounding signals and determined to be reliable lipid biosignatures for living biofabric builders and tenant microorganisms. Builder and tenant microbial biosignatures were linked to specific Cyanobacteria, anoxygenic phototrophs, and heterotrophs, which are prominent members of the living communities. Upon lithification and burial, silicon isotopes of silicified biomass began to re‐equilibrate, increasing from δ30Si −2‰ in living biomats to −0.55‰ in lithified samples. Active endolithic microbial communities were identified in lithified samples and were dominated by Cyanobacteria, heterotrophic bacteria, and fungi. Results indicate that distinct microbial communities build and inhabit silicified biofabrics through time and that microbial biosignatures shift over the course of lithification. These findings improve our understanding of how microbial communities silicify, the biomarkers they retain, and transitionary impacts that may occur through lithification and burial. [ABSTRACT FROM AUTHOR]

The selective separation of ions from aqueous systems, and even in the human body, is a crucial to overall environmental management and health. Nanoporous materials are widely known for their selective removal of cations from aqueous media, and therefore have been targeted for use as a pharmaceutical to treat hyperkalemia. This study investigated the detailed crystallographic molecular mechanisms that control the potassium ion selectivity in the nanoporous cubic zirconium silicate (CZS) related materials. Using time-resolved in situ Raman spectroscopy and time-resolved in situ X-ray diffraction, the selectivity mechanisms were determined to involve a synchronous cation-cation repulsion process that serves to open a favorable coordination bonding environment for potassium, not unlike the ion selectivity filter process found in potassium ion channels in proteins. Enhancement of ion exchange was observed when the CZS material was in a partial protonated state (≈3:1 Na:H), causing an expansion of the unit-cell volume, enlargement of the 7 member-ring window, and distortion of framework polyhedra, which allowed increased accessibility to the cage structures and resulted in rapid irreversible potassium ion exchange. [ABSTRACT FROM AUTHOR]

A phase featuring decorated, A-type trivacant alpha-Keggin ions linked by their charge-balancing sodium cations was isolated and structurally characterized as a part of heteropolybiobate chemistry investigations. This heteropolyniobate has a true lacunary structure type and like other heteropolyniobate compounds this phase was found to be more characteristic of a rigid framework of heteropolyanions linked by sodium cations rather than a water-soluble heteropolyanion salt.

The origin of pisoids in a diversity of environments has been recently discussed. While traditionally considered physico‐chemical sedimentary products developed in turbulent environments, or even grown in situ, new results show that microbes may influence their development. In the Terma Los Hornos travertine system, two types of actively forming pisoids were recognized: (i) laminated pisoids with a concentrically laminated crust surrounding a nucleus; and (ii) dendriform radial pisoids with no distinct nucleus. Laminated pisoids form in turbulent pools at the base of waterfalls, while dendritic pisoids develop within small depressions between terracettes, and they can occur superposed as a result of episodic transport and recycling within the travertine system (for example, dendritic textures as nucleus of laminated pisoids). The laminated pisoids are characterized by laterally constant laminae thickness with high inheritance and low amounts of randomly distributed organic matter and microbial remains, suggesting a predominantly abiogenic origin. In contrast, the dendritic pisoids exhibit an intimate relationship with diatoms and filamentous bacteria suggesting a stronger biotic influence in their formation. Thus, both abiogenic and biogenic carbonate structures can coexist in the same hydrothermal system. Pisoids found in the stratigraphic record of Terma Los Hornos allowed to test the preservation potential of the primary signals and reconstructing early diagenetic overprints. [ABSTRACT FROM AUTHOR]

As the exploration of Mars and other worlds for signs of life has increased, the need for a common nomenclature and consensus has become significantly important for proper identification of nonterrestrial/non-Earth biology, biogenic structures, and chemical processes generated from biological processes. The fact that Earth is our single data point for all life, diversity, and evolution means that there is an inherent bias toward life as we know it through our own planet's history. The search for life "as we don't know it" then brings this bias forward to decision-making regarding mission instruments and payloads. Understandably, this leads to several top-level scientific, theoretical, and philosophical questions regarding the definition of life and what it means for future life detection missions. How can we decide on how and where to detect known and unknown signs of life with a single biased data point? What features could act as universal biosignatures that support Darwinian evolution in the geological context of nonterrestrial time lines? The purpose of this article is to generate an improved nomenclature for terrestrial features that have mineral/microbial interactions within structures and to confirm which features can only exist from life (biotic), features that are modified by biological processes (biogenic), features that life does not affect (abiotic), and properties that can exist or not regardless of the presence of biology (abiogenic). These four categories are critical in understanding and deciphering future returned samples from Mars, signs of potential extinct/ancient and extant life on Mars, and in situ analyses from ocean worlds to distinguish and separate what physical structures and chemical patterns are due to life and which are not. Moreover, we discuss hypothetical detection and preservation environments for extant and extinct life, respectively. These proposed environments will take into account independent active and ancient in situ detection prospects by using previous planetary exploration studies and discuss the geobiological implications within an astrobiological context. [ABSTRACT FROM AUTHOR]

A high-pressure neutron powder diffraction experiment is performed to locate the hydrogen atoms and elucidate the details of the hydrogen-bonding network. The experiment allows the first complete description of this system and provides an opportunity to understand all aspects of the reversible nature of the pressure-induced hydration (PIH).

Time-resolved X-ray and neutron scattering with theoretical calculations have shown a mechanism whereby hydrogen crystalline silicotitanate (H-CST) has achieved its remarkable ion-exchange selectivity for cesium. The studies have shown that the interactions have induced a subtle conformational rearrangement in CST that unlocks the preferred Cs site and increases the overall capacity and selectivity for ion exchange.

A new potassium gallosilicate zeolite with a natrolite topology is prepared under hydrothermal conditions and characterized as a function of temperature by using monochromatic synchrotron X-ray powder diffraction and Rietveld analyses. It is shown that the distribution of potassium cations within the channels is unperturbed during the water rearrangements and their order-disorder transition within the channels.

The crystal structure of the selective [Cs.sup.+] ion exchanger [D.sub.1.6][H.sub.0.4])[Ti.sub.2]Si[O.sub.7].[D.sub.2.66][H.sub.0.34][O.sub.1.5], known as crystalline silicotitanate (CST) is determined by powder neutron diffraction study. There is new geometric arrangement of the water-deutroxyl network in (Cs, D)-CST which suggests that [D.sub.water]-[D.sub.deuteroxyl] repulsion forced by [Cs.sup.+] exchange drives the structural transformation.

The synthesis and structure of tribasic lead maleate hemihydrate and lead maleate is described. The structure of lead maleate hemihydrate consists of infinite slabs of edge-sharing OPb(sub 4) tetrahedra, linked together into a 3D network by tetradentate deprotonated maleate ligands while lead maleate shows a lamellar structure and contains double layers of heptacoordinated lead atoms, bonded only to the oxygen atoms of the maleate ligands.

Phoxite, (NH4)2Mg2(C2O4)(PO3OH)2(H2O)4, is a new mineral species from the Rowley mine, Maricopa County, Arizona, U.S.A., and it has potential uses in agricultural applications for soil conditioning, fertilizing, and as a natural pesticide. It was found in an unusual bat-guano-related, post-mining assemblage of phases that include a variety of vanadates, phosphates, oxalates, and chlorides, somecontaining NH+. Other secondary minerals found in association with phoxite are antipinite, aphithitalite, 4bassanite, struvite, thenardite, and weddellite. Crystals of phoxite are colorless composite blades upto about 0.4 mm. The streak is white, and the luster is vitreous to oily. The Mohs hardness is 2½, the tenacity is brittle, fracture is irregular, there is fair {100} cleavage, and the measured density is 1.98(2) g/cm3. Phoxite is optically biaxial (–) with α = 1.499(1), β = 1.541(1), γ = 1.542(1) (white light); 2V = 16(1)°; dispersion r < v, slight; orientation Y = b, X ^ a ≈ 9° in obtuse β. Electron microprobe analyses yielded the empirical formula [(NH4)1.77K0.23]Σ2Mg2.00(C2O4)(PO3OH)2(H2O)4, with the C and H content inferred from the crystal structure. Raman spectroscopy confirmed the presence of NH4 and C2O4. Phoxite is monoclinic, P21/c, with a = 7.2962(3), b = 13.5993(4), c = 7.8334(6) Å, β = 108.271(8)°, V = 738.07(7) Å3, and Z = 2. In the crystal structure of phoxite (R1 = 0.0275 for 1147 Io > 2σI reflections), bidentate linkages between C2O4 groups and Mg-centered octahedra yield chains, which link to one another via PO3OH tetrahedra to create undulating [Mg2(C2O4)(PO3OH)2(H2O)4]2– sheets. Strong hydrogen bonds link the sheets into a "soft framework," with channels containing 44NH+. The NH+ forms both ordered hydrogen bonds and electrostatic bonds with O atoms in the framework. Phoxite is the first mineral known to contain both phosphate and oxalate groups as essential components. [ABSTRACT FROM AUTHOR]