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When and where was Mars warm and wet? Widespread bedrock exposures of clay minerals on Mars point to the presence of liquid water in the distant past. The prospect that the planet was once much warmer and wetter than now prompts the question: was early Mars habitable? In a review of data collected in the past decade, Bethany Ehlmann et al . conclude that warm and humid conditions did prevail — not on the planet's surface but beneath it. Mars's surface has probably been cold and dry for more than 4 billion years, with potentially habitable environments limited to the subsurface. Clay minerals, recently discovered to be widespread in Mars’s Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter than at present. However, available data instead indicate substantial Martian clay formation by hydrothermal groundwater circulation and a Noachian rock record dominated by evidence of subsurface waters. Cold, arid conditions with only transient surface water may have characterized Mars’s surface for over 4 billion years, since the early-Noachian period, and the longest-duration aqueous, potentially habitable environments may have been in the subsurface.

Clay-based nanomaterials, especially 2:1 aluminosilicates such as vermiculite, biotite, and illite, have demonstrated great potential in various fields. However, their characteristic sandwiched structures and the lack of effective methods to exfoliate two-dimensional (2D) functional core layers (FCLs) greatly limit their future applications. Herein, we present a universal wet-chemical exfoliation method based on alkali etching that can intelligently “capture” the ultrathin and biocompatible FCLs (MgO and Fe 2 O 3 ) sandwiched between two identical tetrahedral layers (SiO 2 and Al 2 O 3 ) from vermiculite. Without the sandwich structures that shielded their active sites, the obtained FCL nanosheets (NSs) exhibit a tunable and appropriate electron band structure (with the bandgap decreased from 2.0 eV to 1.4 eV), a conductive band that increased from −0.4 eV to −0.6 eV, and excellent light response characteristics. The great properties of 2D FCL NSs endow them with exciting potential in diverse applications including energy, photocatalysis, and biomedical engineering. This study specifically highlights their application in cancer theranostics as an example, potentially serving as a prelude to future extensive studies of 2D FCL NSs. Clay-based nanomaterials are of wide interest but problems extracting the 2D functional core layers have limited potential applications. Here, the authors report on the wet exfoliation of vermiculite by alkali etching to obtain the core layers and explore the application of the materials in cancer theranostics.

Background Mica is widely applied in cosmetics, construction, automotive, electronics, defense, and medical industries, particularly important in cosmetics as an ingredient in foundations, eyeshadows, lipsticks, and nail polishes for its pearlescent and shimmering effects. Aims To evaluate the suitability of mica minerals from Bangladeshi river sands for cosmetic applications by investigating their chemical composition, heavy metal content, potential for skin irritation, and antimicrobial activity. Methods The chemical composition, crystallographic structure, and heavy metal content of mica samples were analyzed using X‐ray fluorescence, X‐ray diffraction, and Atomic Absorption Spectroscopy. Non‐carcinogenic and carcinogenic risks were evaluated using USEPA models (ADD, HQ, HI, LADD, ILTCR). Sensory evaluation was performed by 10 trained panelists, while primary skin irritation was tested on albino rabbits. Antimicrobial activity against bacterial and fungal strains was assessed using agar well diffusion and broth microdilution assays. Results Muscovite contained high Al2O3 (30.46%) and SiO2 (49.29%), whereas biotite and phlogopite were enriched in Fe2O3 (43%) and MgO, supporting shimmer, color, and UV‐protective properties. XRD confirmed high crystallinity and purity. Heavy metals were within safe dermal and inhalation exposure limits. Sensory evaluation showed a silky texture, strong adhesion, and a luminous finish. All samples were non‐irritant (PII = 0.00). Biotite and phlogopite exhibited moderate antibacterial activity against Staphylococcus aureus, Salmonella typhi, and Bacillus megaterium, but no antifungal effects. Conclusions Muscovite, biotite, and phlogopite mica exhibit low heavy metal content, non‐irritant and non‐carcinogenic behavior, moderate antibacterial activity, and favorable sensory properties, highlighting their potential as safe, effective, and multifunctional ingredients for cosmetic applications.

Solid progress for hydrogels Hydrogels are mouldable polymeric materials made mostly of water, used for example as cell tissue cultures and in prosthetics. Hydrogels held together by non-covalent interactions usually have poor mechanical properties, whereas the rather stronger covalently bonded hydrogels cannot self-heal if cut and tend to be brittle. The idea that water-based hydrogels might be developed as environmentally friendly substitutes for conventional petroleum-based plastics in some applications, bringing novel properties with them, comes a little closer with the development of a supramolecular (non-covalent) hydrogel that is a solid thanks to the presence of small quantities of non-water ligands — 3% clay and tiny amounts of an organic binder. This new gel is capable of self-healing, is exceptionally resilient and can be moulded into free-standing shapes that can also be fused together to form more complex architectures. In the search to reduce our dependency on fossil-fuel energy, new plastic materials that are less dependent on petroleum are being developed, with water-based gels — hydrogels — representing one possible solution. Here, a mixture of water, 3% clay and a tiny amount of a special organic binder is shown to form a transparent hydrogel that can be moulded into shape-persistent, free-standing objects and that rapidly and completely self-heals when damaged. With the world’s focus on reducing our dependency on fossil-fuel energy, the scientific community can investigate new plastic materials that are much less dependent on petroleum than are conventional plastics. Given increasing environmental issues, the idea of replacing plastics with water-based gels, so-called hydrogels, seems reasonable. Here we report that water and clay (2–3 per cent by mass), when mixed with a very small proportion (<0.4 per cent by mass) of organic components, quickly form a transparent hydrogel. This material can be moulded into shape-persistent, free-standing objects owing to its exceptionally great mechanical strength, and rapidly and completely self-heals when damaged. Furthermore, it preserves biologically active proteins for catalysis. So far 1 no other hydrogels, including conventional ones formed by mixing polymeric cations and anions 2 , 3 or polysaccharides and borax 4 , have been reported to possess all these features. Notably, this material is formed only by non-covalent forces resulting from the specific design of a telechelic dendritic macromolecule with multiple adhesive termini for binding to clay.

Natural antibacterial clays, when hydrated and applied topically, kill human pathogens including antibiotic resistant strains proliferating worldwide. Only certain clays are bactericidal; those containing soluble reduced metals and expandable clay minerals that absorb cations, providing a capacity for extended metal release and production of toxic hydroxyl radicals. Here we show the critical antibacterial components are soluble Fe 2+ and Al 3+ that synergistically attack multiple cellular systems in pathogens normally growth-limited by Fe supply. This geochemical process is more effective than metal solutions alone and provides an alternative antibacterial strategy to traditional antibiotics. Advanced bioimaging methods and genetic show that Al 3+ misfolds cell membrane proteins, while Fe 2+ evokes membrane oxidation and enters the cytoplasm inflicting hydroxyl radical attack on intracellular proteins and DNA. The lethal reaction precipitates Fe 3+ -oxides as biomolecular damage proceeds. Discovery of this bactericidal mechanism demonstrated by natural clays should guide designs of new mineral-based antibacterial agents.

The synthesis of the Al 2 SiO 5 polymorphs kyanite, sillimanite and andalusite in a pure Al 2 O 3 –SiO 2 –H 2 O (ASH) system has long been known to be impeded. In order to decipher individual aspects of the reaction: corundum + SiO 2 aq , which repeatedly fails to produce thermodynamically stable Al 2 SiO 5 , we conducted experiments within the stability fields of kyanite and sillimanite (500–800 ℃; 0.2–1 GPa) with the aim of forming reaction coronas on corundum. Results showed that metastable corundum + quartz assemblages form persistently in pure ASH, even in Al 2 SiO 5 seeded experiments, despite the presence of catalyzing fluid and evidence of fast reaction kinetics. Coronas on corundum spontaneously formed when additional components (Na, K, N, and Mg) were added to the experiment. In a similar experiment with baddeleyite (ZrO 2 ) instead of corundum in silica saturated water, a zircon corona formed readily. This implies that nucleation and growth of Al 2 SiO 5 is obstructed under conditions of Al and Si saturation in aqueous fluid, while both corundum and quartz saturated aqueous fluid are willing participants in other reactions towards stable corona formation. Instead of Al 2 SiO 5 precipitation, an unexpected fluid-aided silica diffusion process into corundum was documented. The latter included the formation of nanometer wide hydrous silicate layers along the basal plane of the corundum host, which enhanced the silica diffusion rate drastically, leading to silica supersaturation in the host mineral, and ultimately to precipitation of quartz inside corundum. We conclude that the natural metastable assemblage of quartz and corundum is not necessarily the result of dry or fluid absent conditions, given that the aqueous fluid in experiments does not promote Al 2 SiO 5 formation, but rather seems to support the formation and preservation of a metastable assemblage.

Background Imogolite is a naturally occurring hollow aluminosilicate nanotube with potential for engineered applications due to its high aspect ratio, hydrophilicity, and polarization. However, these same features raise concerns about potential adverse health effects. These concerns parallel those associated with multi-walled carbon nanotubes (MWCNTs), which are known to cause inflammation, fibrosis, and cardiovascular effects. The purpose of this study was to investigate how surface functionalization of imogolite influences its toxicity and biological response, with the aim of informing safer design of nanomaterials. Female C57BL/6J mice were exposed via intratracheal instillation to 6, 18, or 54 µg of hydroxylated (Imo-OH) or methylated (Imo-CH 3 ) imogolite. Toxicity was assessed at day 1, 28 and 90 post-exposure, with carbon black (Printex90) nanoparticles as a benchmark. Pulmonary inflammation and systemic acute-phase response were assessed as key indicators of chronic health effects. Results Physicochemical characterization showed that Imo-OH dispersed as single nanotubes, while Imo-CH 3 formed bundles, impacting surface accessibility. Both variants induced strong pulmonary inflammation, but Imo-OH elicited a stronger and more persistent neutrophil influx, lymphocyte recruitment, and acute-phase response. Cytotoxicity was low, though elevated total protein in bronchoalveolar lavage fluid indicated altered alveolar-capillary barrier integrity, especially for Imo-OH. Lung histopathology confirmed more severe lung lesions, macrophage aggregates, and type II pneumocyte hyperplasia in the Imo-OH group. Benchmark dose modeling revealed that Imo-OH’s inflammatory potential surpassed other high aspect ratio nanomaterials. Conclusions Both imogolite variants induced pulmonary inflammation and an acute-phase response in mice; however, these effects were markedly reduced for the methylated imogolite (Imo-CH 3 ). In addition to surface functionalization, factors like bundle formation and by-product particles may also influence toxicity. These findings emphasize the pivotal role of surface chemistry—and associated structural properties—in shaping the biological response to nanomaterials, reinforcing the need for thoughtful design strategies to promote safer applications in nanotechnology. Graphical abstract

During flight, many silicates (sand, dust, debris, fly ash, etc.) are ingested by an engine. They melt at high operating temperatures on the surface of thermal barrier coatings (TBCs) to form calcium-magnesium-aluminum-silicate (CMAS) amorphous settling. CMAS corrodes TBCs and causes many problems, such as composition segregation, degradation, cracking, and disbanding. As a new generation of TBC candidate materials, rare-earth zirconates (such as Sm 2 Zr 2 O 7 ) have good CMAS resistance properties. The reaction products of Sm 2 Zr 2 O 7 and CMAS and their subsequent changes were studied by the reaction of Sm 2 Zr 2 O 7 and excess CMAS at 1350 °C. After 1 h of reaction, Sm 2 Zr 2 O 7 powders were not completely corroded. The reaction products were Sm-apatite and c-ZrO 2 solid solution. After 4 h of reaction, all Sm 2 Zr 2 O 7 powders were completely corroded. After 24 h of reaction, Sm-apatite disappeared, and the c-ZrO 2 solid solution remained.

Aluminum silicate nanofibers (ASNFs) have attracted significant attention due to their excellent stability and high-temperature properties. Al 2 O 3 -SiO 2 aerogel (ASAs) has high porosity and low thermal conductivity, but its mechanical properties need to be improved. Reinforcing aerogels with fibers can lead to remarkable enhancements in their properties. Reducing the fiber diameter has proven to be an effective means of improving the structural integrity and mechanical stability of aerogel composites. In the context of this study, we prepared aluminum silicate nanofibers (ASNFs) with a diameter of 170 nm through the utilization of electrostatic spinning. These ASNFs were then successfully integrated with aluminum silicate aerogels (ASAs) to create a novel composite material known as aluminum silicate nanofiber-reinforced Al 2 O 3 -SiO 2 aerogel (AS/ASNFAs). Its microstructure, mechanical properties and heat insulation properties have been researched. The results show that the compressive strength of AS/ASNFAs (0.44 MPa) is significantly higher than that of Al 2 O 3 -SiO 2 aerogel (0.16 MPa). Meanwhile, the AS/ASNFAs has high specific surface area (600 m 2 /g), low density (0.15 g/cm 3 ), and low thermal conductivity (0.026 W/(m·K)). This work provides a useful solution to improve the comprehensive properties of Al 2 O 3 –SiO 2 aerogel composites. Graphical Abstract Highlight An aluminum silicate nanofiber-reinforced Al 2 O 3 -SiO 2 aerogel (AS/ASNFAs) has been prepared by sol-gel method. Addition of aluminum silicate nanofibers (ASNFs) improves mechanical properties of Al 2 O 3 -SiO 2 aerogel (ASAs), and compressive strength of AS/ASNFAs-0.2 (0.44 MPa) is more than twice that of ASAs (0.16 MPa). Low thermal conductivity (0.026 W/(m·K)) is achieved for AS/ASNFAs-0.1. Due to the good dispersion of ASNFs in ASAs, the interaction of them not only improves mechanical properties of AS/ASNFAs but also increases thermal stability at high temperature.

The experiments presented here are based on the reconfiguration of an ancient medicine, Lemnian Earth (LE) ( terra sigillata , stamped earth , sphragis ), an acclaimed therapeutic clay with a 2500-year history of use. Based on our hypothesis that LE was not a natural material but an artificially modified one involving a clay-fungus interaction, we present results from experiments involving the co-culture of a common fungus, Penicillium purpurogenum ( Pp ), with two separate clay slurries, smectite and kaolin, which are the principal constituents of LE. Our results show: (a) the leachate of the Pp +smectite co-culture is antibacterial in vitro , inhibiting the growth of both Gram-positive and Gram-negative bacteria; (b) in vivo , supplementation of regular mouse diet with leachates of Pp +smectite increases intestinal microbial diversity; (c) Pp+ kaolin does not produce similar results; (d) untargeted metabolomics and analysis of bacterial functional pathways indicates that the Pp +smectite-induced microbiome amplifies production of short-chain fatty acids (SCFAs) and amino acid biosynthesis, known to modulate intestinal and systemic inflammation. Our results suggest that the combination of increased microbial diversity and SCFA production indicates beneficial effects on the host microbiome, thus lending support to the argument that the therapeutic properties of LE may have been based on the potential for modulating the gut microbiome. Our experiments involving reconfigured LE open the door to future research into small molecule-based sources for promoting gut health.