Quantifying the viscosity of hydrous volcanic melts is essential for understanding ascent dynamics, degassing efficiency, and fragmentation, yet laboratory measurements may be compromised by syn-analytical evolution in melt structure at the nanoscale, thus yielding viscosity values not representative of a homogeneous melt phase. This issue remains poorly explored in highly polymerized trachytic magmas, for which robust viscosity constraints are scarce despite their relevance to explosive volcanism. We develop a composition-specific viscosity model for the Agnano-Monte Spina (AMS) trachyte using an integrated approach, combining differential scanning calorimetry (DSC), micropenetration viscometry (MP), Brillouin light scattering, and in situ high-temperature Raman spectroscopy. Glass transition temperatures () decrease from 632 degrees C to 349 degrees C, over 0-4.45 wt.% H2O, and melt fragility (a measure of the temperature-sensitivity of viscosity) increases systematically with hydration, consistent with independent configurational heat-capacity data. In situ Raman measurements show that nanoscale structural reorganization begins within minutes once the temperature exceeds . This leads to viscosity increase of up to similar to 1 log unit in MP measurements over a period of one-hour. Instead, single-cycle DSC measurements preserve the melt structure homogeneity and provide reliable constraints for viscosity parameterization. The resulting viscosity model captures the strong, hydration-dependent rheology of the AMS trachyte while avoiding biases introduced by syn-analytical melt structure evolution. Our spectroscopically guided approach offers a transferable strategy for determining pure-liquid viscosity in volatile-bearing magmas, improving the quantitative basis for modeling magma ascent and eruptive behavior.

The eruptive style of mafic volcanoes is critically influenced by magma rheology, which is dynamically modulated by crystallization during cooling and decompression of ascending magma. Although the role of undercooling is well established, the influence of deformation on crystallization kinetics in magmas remains poorly constrained. Here, we experimentally investigate the rheological and textural evolution of Mt. Etna trachybasalt under isothermal conditions (1170 degrees C) using concentric cylinder rheometry at varying shear rates (up to 10 s-1). Real-time viscosity monitoring reveals that stirring exerts a fundamental influence in enhancing magma solidification due to crystallization, shortening the incubation time of nucleation and the time needed to reach thermomechanical equilibrium. Crystal textures confirm that stirring shifts crystallization from growthdominated to nucleation-dominated regimes, with nucleation rates increasing by up to two orders of magnitude at the highest shear rate. Electron back-scatter diffraction analysis of the experimental samples indicates a non-linear structural response to deformation. Low-to-intermediate shear rates (0.1-1 s-1) induce a moderate degree of crystals preferred orientation, while higher shear rate (10 s-1) produces chaotic, isotropic textures due to rapid and spatially dispersed nucleation. These findings outline that deformation actively drives crystallization, dramatically accelerating magma solidification. We discuss how shear-enhanced crystallization is a key mechanism in volcanic systems, facilitating the attainment of rheological thresholds that trigger transitions in eruptive style. These deformation-driven effects offer new constraints for the understanding of basaltic Plinian eruption trigger mechanisms, identifying a threshold above which microlite production and magma strengthening can be significantly accelerated during ascent.

The viscosity of hydrous volcanic melts exerts a primary control on magma ascent, degassing efficiency, and fragmentation, yet its experimental determination is often affected by time-dependent melt structure changes at the nanoscale during measurements. This issue remains poorly constrained for highly polymerised, alkali-rich trachytic magmas, despite their key role in explosive volcanism at caldera systems such as Campi Flegrei (Italy).We investigate the anhydrous and hydrous viscosity of a trachytic melt from the Agnano–Monte Spina (AMS) eruption (Campi Flegrei) by combining differential scanning calorimetry (conventional and flash DSC), micropenetration viscometry (MP), Brillouin light scattering (BLS), and in situ high-temperature Raman spectroscopy. This integrated approach allows us to directly link viscosity behaviour to nanoscale structural evolution during thermal treatments. Glass transition temperature (Tg) decreases from ~632 to ~349 °C with increasing water (0–4.45 wt.%), while melt fragility increases systematically with hydration, independently constrained from BLS elastic moduli measurements.In situ Raman spectroscopy reveals that nanoscale melt structure reorganisation initiates within minutes, slightly above Tg = 632 °C. These processes lead to a viscosity overestimate of up to ~1 log unit in standard viscometry experiments. Using the glass transition temperatures derived from DSC measurements and BLS-derived melt fragilities, we develop a composition-specific viscosity model for the AMS trachytic magma that avoids nanostructuration-induced artefacts.As the AMS trachytic magmas are crystal-poor, its rheology is dominated by the melt phase, making melt viscosity a primary control on magma ascent. Our results show that viscosity is highly sensitive to dehydration, with relatively low initial viscosity at high water content, followed by rapid rheological stiffening during ascent. The new model indicates a 105-fold increase in melt viscosity associated with dehydration from 5 to 0 wt.% H2O, relative to the 104-fold increase calculated using previous experimental and empirical models. As a result, commonly used empirical viscosity laws likely underestimate both the magnitude and rate of viscosity evolution during decompression of hydrous trachytic melts, with significant consequences for degassing efficiency, fragmentation depth, and eruptive style. The spectroscopically guided approach developed in this study is readily applicable to other volatile-bearing magmas and offers a more physically robust rheological framework for modelling viscosity in volcanic systems.

The cataclysmic eruption of Hunga volcano (Tonga-Kermadec arc system) on 15 January 2022, the most powerful explosive volcanic event of the 21st century, underscores the critical need to constrain the pre-eruptive magmatic conditions governing arc volcanoes with shallow marine calderas. In this study, we present results from isobaric-isothermal crystallization experiments conducted on a basaltic andesite representative of primitive magmas at Hunga volcano. Experimental runs were performed at pressures of 200 and 300 MPa, over a temperature range of 1000-1130 degrees C, melt water contents of 0.6-6.4 wt%, and oxygen fugacities between +0.7 and + 3.4 log units relative to the nickel-nickel oxide buffer. Temperature and melt-water content are the primary controls on modal phase assemblages and compositional trends in the experimental charges, exerting a dominant influence on the cotectic crystallization of clinopyroxene and plagioclase, as well as on the stability of orthopyroxene and abundance of magnetite. By integrating experimental data with thermodynamic modeling, orthopyroxene-clinopyroxene thermometry, and plagioclase-based hygrometry, we document that both pre-2022 and 2022 eruptive products at Hunga volcano reflect the differentiation of basaltic andesitic to andesitic magmas at pre-eruptive temperatures of similar to 1050-1130 degrees C and melt-water contents up to similar to 3 wt%. Under the investigated experimental conditions, however, extensive crystallization of plagioclase and magnetite at similar to 1000 degrees C drives the host basaltic andesitic melt toward more evolved dacitic compositions. Dacites have not been reported at Hunga volcano, but they occur in low-temperature, magnetite-bearing phenocryst assemblages on other Tongan islands, particularly in the northern part of the arc. Collectively, our experimental-thermodynamic approach provides compelling evidence for polythermal and polybaric plumbing systems at intra-oceanic arc volcanoes, highlighting the pivotal role of phase stability and mineral chemistry in controlling the differentiation pathways of magmas and the transition from tholeiitic to calc-alkaline affinity.

The influence of excess Na2O on the structure, thermal properties and viscosity of haplogranitic melts was systematically investigated by integrating micro-penetration viscometry, Raman spectroscopy (including Boson peak analysis) and differential scanning calorimetry (DSC). This approach reveals fundamental structure-property relationships in these felsic melt analogs. We demonstrate that Na2O-induced network depolymerization, clearly evidenced by Raman spectroscopy, provides a direct rationale for the observed dramatic, non-linear decrease in melt viscosity and a concurrent systematic increase in melt fragility. Strong correlations are established between melt fragility and both nanoscale vibrational dynamics (Boson peak frequency, omega BP) and macroscopic thermodynamics (configurational heat capacity change at the glass transition temperature, Delta Cconf ( Tg)), validating omega BP and Delta Cconf ( Tg) as proxies for estimating melt fragility in p p experimentally challenging systems, such as those prone to nanostructuration. Furthermore, we provide DSC-viscosity shift factors Konset, Kpeak, Kendset applicable to peralkaline compositions. By addressing the role of thermal lag and thermal inertia in DSC analyses, our study refines the experimental accuracy of viscosity-temperature relationships and reinforces the robustness of the shift-factor approach across compositionally diverse silicate systems. This work thus provides an integrated framework and predictive insights into the rheology of Na2O-rich haplogranitic melts, relevant to understanding evolved magmatic systems.

The 2023-2024 eruptions at Sundhn & uacute;ksgigar in Iceland produced tholeiitic basaltic lavas that traveled at high velocities, affecting vast areas. Under such conditions, disequilibrium crystallization can play a fundamental role in modulating the lava flow dynamics and inundation capacity. To investigate this phenomenon, we carried out a comprehensive rheological characterization of the Sundhn & uacute;ksgigar basalt, analyzing both the liquid phase and the crystal-bearing suspensions under disequilibrium conditions (cooling rates ranging from 0.1 to 10 degrees C/min) and near-equilibrium conditions (at fixed temperatures between 1242 and 1180 degrees C). Our results show that the cooling rate critically influences the extent and timescale of disequilibrium crystallization, thereby shaping the rheological evolution of the melt, leading to distinct deformation response of the crystal-bearing magmatic suspension. Compared to other basalts erupted worldwide, the Sundhn & uacute;ksgigar melt exhibits two main features: i) an exceptionally low rate of viscosity increase induced by crystallization and ii) the ability to crystallize even at the highest cooling rates applied during the experiments. These characteristics may contribute to enhancing the efficiency of external crust formation, limiting heat loss from the inner portion of the lava flow, which consequently cools more slowly. Thermal insulation effects reduce the rate of viscosity increase during lava emplacement, a key factor in determining lava flow inundation potential. Our findings underscore the critical role of disequilibrium crystallization in governing the rheological evolution and emplacement dynamics of basaltic lavas, offering new insights into lava flow behavior.

Explosive volcanic eruptions pose significant threats to populated areas by injecting substantial amounts of gas and ash into the atmosphere. These events, resulting from magma fragmentation, are triggered by factors such as limited bubble expansion and relatively high strain rates during ascent, predominantly controlled by chemical composition. Less evolved melts, like andesites and basalts, present challenges in achieving fragmentation conditions due to their inherently low viscosities. Despite this, explosive activity of these magmas occurs. Recent studies highlight the role of Fe-Ti-oxide nanocrystals (nanolites) in increasing viscosity during laboratory measurements. Interestingly, nanolites have been found in natural volcanic products erupted during explosive events. However, the mechanisms and the extent to which nanolite formation affects magma viscosity remain a subject of ongoing debate. Here, we present the first in situ imaging observation of nanolite formation in andesitic melt and thoroughly quantify the impact on melt viscosity. To establish a robust point of comparison, we develop multiple novel viscosity models exclusively using viscosity data from nanolite-free samples. Our findings reveal that above the glass transition temperature, iron oxidation and nanocrystallization readily occur, inducing structural heterogeneities in the nanoscale. The precipitation of magnetite nanocrystals induces a heterogeneous distribution of elements in the residual melt, generating a relatively SiO2-enriched matrix and Al-enriched shells around the nanolites. This phenomenon results in a substantial, up to 30-fold, surge in magma viscosity at eruptive temperatures. This noteworthy increase in magma viscosity has profound implications for the physical properties of andesitic plugs and domes and could play a critical role in driving the magma towards fragmentation during eruption.

The dynamic interplay between magmas and carbonate wall rocks within volcanic plumbing systems heavily influences the chemical and physical properties of erupted magmas. In this study we present results from isothermal static experiments (ISEs) and isothermal deformation experiments (IDEs) aimed at investigating the rheological evolution of a phonotephritic melt from Somma-Vesuvius (Italy) under variable shear rates and CaO and CaO + MgO doping levels. Flash differential scanning calorimetry is also used to determine the viscosity of interstitial melt, allowing for the first direct assessment of how crystallization affects melt rheology without relying on empirical viscosity models. Two distinct rheological scenarios emerge from IDEs: 1) a viscous deformation, characterized by uniform flow, and 2) a non-homogeneous deformation, featuring shear localization and viscous/brittle rupture of the magma. As both shear rate and doping level increase, a non-Newtonian melt behavior is observed due to stress localization and rupture, facilitated by the development of the crystal network. The narrower viscosity range measured from IDEs, compared to models of pure viscous behavior, suggests that shear localization and fracturing reduce the resistance to flow in doped, crystal-rich samples. The complex rheology of doped melts reflects the disaggregation of skarn shells at the margins of magma chambers, thereby facilitating skarn recycling and enhancing magma contamination.

Accurate determination of melt viscosity near the glass transition temperature (T-g) is critical for modeling volcanic processes, but direct measurements are often compromised by nanostructuration in natural Fe-Ti-bearing systems, especially during experimental manipulation. Differential scanning calorimetry (DSC) offers an alternative method for estimating viscosity via "shift factors" (K), which link enthalpy to shear relaxation (and thus shear viscosity). This is possible because DSC analysis of supercooled melts requires significantly less time than micropenetration viscometry. However, the compositional sensitivity of the shift factors is still debated, particularly in highly polymerized melts. To address this, we investigated the role of Al2O3 in controlling melt viscosity and network structure using five Fe-Ti-free haplogranitic compositions: the metaluminous HPG8 base melt and four systematically modified variants with nominal composition of +2, +5, -2 and -5 wt% Al2O3. We combine micropenetration viscometry, DSC, and Raman spectroscopy to examine the rheological and structural response to Al2O3 variation. Our results reveal a non-linear viscosity dependence on Al2O3 content: peraluminous melts exhibit higher viscosities and T-g, while peralkaline melts are significantly more fluid. Despite these differences, melt fragility remains constant across the compositional series. Calibrated DSC shift factors show no correlation with the network modifier content in peralkaline melts but instead they scale with the infinite-temperature viscosity (log(10)eta(infinity)). Peralkaline melts with log(10)eta(infinity) > -3.00 show low and constant shift factors, whereas metaluminous and peraluminous melts (log(10)eta(infinity) < -3.00) yield higher values. These findings establish benchmarks for the application of the DSC shift-factor approach to estimate melt viscosity in natural, silica-rich rhyolitic melts, especially where direct measurements are hindered, thereby improving our ability to model magma rheology and eruption dynamics.

Explosive volcanic eruptions, driven by magma fragmentation, pose significant geohazards due to their rapid energy release and widespread dispersal of pyroclasts. High magma viscosity promotes brittle fragmentation by limiting volatile escape and enhancing internal pressure buildup. Although recent studies have recognized that iron-titanium oxide nanocrystal formation increases melt viscosity, the mechanisms underlying this effect remain poorly constrained. Here we quantify the influence of nanocrystallization on magma viscosity by developing viscosity models that incorporate iron-titanium variations, calibrated against nanocrystal-free andesitic melts. Using time-resolved imaging, we show that nanocrystals form within seconds within synthetic andesitic melts. This process generates nanoscale chemical heterogeneities, including silica enrichment in the surrounding melt and aluminum-rich shells embedding the nanocrystals. These heterogeneities result in viscosity increases of up to 30-fold at eruptive temperatures. Our findings indicate that nanocrystallization modulates magma rheology during early crystallization, with direct implications for the dynamics of andesitic eruptions.

Magma ascending through Earth's crust undergoes complex chemical and physical changes that may induce crystallization, a solidification process that deviates from the thermodynamic state of equilibrium. The diverse cooling and deformative regimes suffered by magmas heavily influence crystallization rates, solidification timescales, and consequently, the rheological evolution of magma. This, in turn, significantly impacts the dynamics of volcanic plumbing systems and the associated eruptive styles. We investigate the rheological changes in Stromboli magma (Italy) during disequilibrium crystallization under non-isothermal sub-liquidus conditions. By systematically varying the cooling rate (1-10 °C/min) and the shear rate (1-10 s-1), we found that cooling rates significantly influence the solidification path of the basalt, while shear rates have a subordinate effect. By comparing our results with literature data on basalts from Mt. Etna (Italy), we observed distinct timescales and rates of solidification, contributing to unique eruptive dynamics in these volcanic plumbing systems.

AbstractHigh‐temperature Raman spectroscopy offers a cost‐effective alternative to extensive infrastructure and sensitive instrumentation for investigating nanolite crystallization in undercooled volcanic melts, a key area of interest in volcanology. This study examined nanolite formation in anhydrous andesite melts in situ at high temperatures, identifying distinct Raman peaks at 310 and 670 cm−1 appearing above the glass transition temperature. The initial amorphous glass remained stable up to 655°C, beyond which Fe‐Ti‐oxide nanolites progressively formed at higher temperatures, as also confirmed by complementary XRD analysis. The evolution of the 310 cm−1 peak depends only on the magnitude of nanolite crystallization, while the intensity of the 670 cm−1 peak is temperature‐dependent and challenging to observe above 500°C. Complementary low‐temperature rock‐magnetic analyses confirmed Fe‐Ti‐oxide nanocrystallization with nanolites around 20 nm in diameter. The study tested lasers of different wavelengths (from 355 to 514 nm) and found the green laser to be the most effective for collecting spectra at both room and high temperature. However, above 720°C, black body radiation significantly hinders Raman observation with the green laser when using a non‐confocal setup and analyzing poorly transparent samples. If higher temperature measurements are desired, switching to a confocal setup and using lower wavelength lasers should be considered. This research offers a protocol for studying nanolite formation and melt dynamics at high temperatures, providing a foundation for future studies of volcanic processes.

Glass forms when a liquid is fast cooled preventing crystallization, across a reversible process known as the glass transition. Organic tissues are commonly preserved as glass by processes of vitrification at very low temperatures, known as cryopreservation, and can return to their original soft state when heated back to ambient temperature. It would therefore be impossible to find organic glass embedded in volcanic deposits that have reached several hundred of Celsius degrees. Here we demonstrate that material with glassy appearance found within the skull of a seemingly male human body entombed within the hot pyroclastic flow deposits of the 79 CE Vesuvius eruption formed by a unique process of vitrification of his brain at very high temperature, and is the only such occurrence on Earth. Calorimetric analyses show that the temperature at which the brain transformed into glass was well above 510 °C, implying that the body was exposed to the passage and vanishing of a short-lived, dilute and much hotter pyroclastic flow, explaining its early fast heating and the following very fast cooling. The glass that formed as a result of such a unique process attained a perfect state of preservation of the brain and its microstructures.

The emplacement of magma chambers within a carbonate basement promotes a sequence of thermochemical reactions that progressively evolve from the carbonate wall-rock towards the magma, altering the chemical composition of the overall system (crystal + melt). Recent petrological and experimental studies highlight that varying degrees of limestone/dolostone assimilation controls the liquid line of descent of magmas, promoting or hindering the crystallization onset of distinct mineral phases.In this study, we investigate how differing degrees of limestone/dolostone assimilation and deformation regimes impact the rheology of a leucite-bearing phonotephrite magma from Somma-Vesuvius (Italy). Using starting materials doped with 0, 10, or 20 wt.% of CaO and CaO+MgO, mimicking the effects of limestone/dolostone assimilation, we conducted two sets of crystallization experiments at 1180°C under static and dynamic conditions (shear strain rate of 1 and 5 s-1). We observe distinct rheological behaviours among melts as a function of composition and applied shear rate, displaying significant differences in terms of crystallizing mineral phases (±clinopyroxene±melilite±leucite±nepheline in the CaO-doped samples and ±clinopyroxene±melilite±olivine±leucite±nepheline, in the CaO+MgO-doped ones) and final crystal contents. Increased alkaline earth content (both Ca and Ca+Mg) alongside higher shear rates foster crystallization, leading to heightened crystal fractions (up to 51%) and larger crystals. Consequently, in heavily doped samples and under high shear rates, viscosity increased of up to 1.5 Log Pa s due to crystallization, causing the rheological transition from coherent flow to shear localization, culminating in physical separation (i.e., viscous rupture). This study underscores the significant influence of deformation on magma, affecting both mineralogical assemblages and crystallization efficiency. These effects compound the pivotal role played by changing magma composition due to carbonate assimilation, governing magma’s crystallization capability, transport properties, and flow behaviour during its ascent from depth to surface.

Purpose. This paper aims to present a unique perspective that emphasizes the intricate interplay between energy, dietary proteins, and amino acid composition, underscoring their mutual dependence for health-related considerations. Energy and protein synthesis are fundamental to biological processes, crucial for the sustenance of life and the growth of organisms. Methods and Results. We explore the intricate relationship between energy metabolism, protein synthesis, regulatory mechanisms, protein sources, amino acid availability, and autophagy in order to elucidate how these elements collectively maintain cellular homeostasis. We underscore the vital role this dynamic interplay has in preserving cell life. Conclusions. A deeper understanding of the link between energy and protein synthesis is essential to comprehend fundamental cellular processes. This insight could have a wide-ranging impact in several medical fields, such as nutrition, metabolism, and disease management.

Cancer cells require substantial amounts of energy and substrates for their metabolic hyperactivity, enabling the synthesis of new cells at the expense of healthy ones. Preliminary in vitro data suggest that a mix of free essential amino acids (EAA-mix) can promote cancer cell apoptosis by enhancing autophagy. This study aimed to confirm, both in vitro and in vivo, whether EAA intake could influence the development of colon cancer in mice. We investigated changes in cancer proliferation in CT26 cells treated with EAA-mix and in mice fed with EAA-rich modified diets (EAARD) as compared to those on a standard laboratory diet (StD). CT26 cells were injected subcutaneously (s.c.) or intraperitoneally (i.p.). After 21 days, tumors were removed and measured. In vitro data corroborated that EAA-mix impairs cancer growth by inducing apoptosis. In vivo data revealed that mice on StD developed significantly larger (s.c.) and more numerous (i.p.) cancers than those on EAARD. EAA administration appears to influence cancer cell survival with notable antiproliferative properties.

Most of the solidification history of magmas beneath active volcanoes takes place in chemically and physically perturbed plumbing systems where the growth of crystals is collectively governed by a range of kinetic processes related to the dynamics of crustal reservoirs and eruptive conduits. In this context, we have experimentally investigated the partitioning of major, minor, and trace cations between plagioclase and trachybasaltic melt under conventional static (no physical perturbation) and dynamic (melt stirring) crystallization regimes. Slow interface reaction kinetics are established between the advancing crystal surface and the adjacent melt, as the result of the combined control of a small degree of effective undercooling, prolonged diffusive relaxation, and convective homogenization. The kinetic aspects of plagioclase growth influence the partitioning of trace cations during transport of structural units across the crystal-melt interface, with consequent departure from macroscopic equilibrium in the system. The type and number of charge-balanced and -imbalanced configurations produced by the accommodation of trace cations into the coordination polyhedron can be thermodynamically rationalized in terms of lattice strain and electrostatic partitioning energetics. However, the overall solution energy accompanying trace cation kinetic substitutions cannot be entirely deconvoluted from major component activities in both melt and plagioclase phases. The emerging view that slow interface kinetic processes may lead to strong compositional dependence for the partition coefficient in dynamic subvolcanic environments contrasts markedly with the conventional idea that the energetics of cation partitioning are dominantly controlled by the effect of isothermal changes in the bulk system.

Abstract Explosive volcanic eruptions, resulting from magma fragmentation, pose significant threats to inhabited regions. The challenge of achieving fragmentation conditions in less evolved compositions, such as andesites and basalts, stems from their low viscosities. Recent research highlights the role of Fe-Ti-oxide nanocrystals (nanolites) in increasing melt viscosity, yet the mechanisms behind the impact of nanocrystallization remain a subject of ongoing debate. To assess their effect on melt viscosity, we introduce innovative viscosity models exclusively utilizing nanolite-free viscosity data. Our study unveils the first in-situ imaging of nanolite formation in andesitic melt resulting in a heterogeneous distribution of elements, generating a relatively SiO2-enriched matrix and Al-enriched shells around nanolites. This phenomenon results in a substantial, up to 30-fold increase in magma viscosity at eruptive temperatures. By incorporating nanoscale observations of fragmented magma from the literature, we deduce that elemental heterogeneities might play a critical role in driving magmas towards failure conditions.

Interaction between magma and carbonate plays a pivotal role in volcanic systems, yet its impact on magma transport properties remains inadequately explored. This study presents novel viscosity data on a leucite-bearing phonotephritic melt from the 472 CE Pollena eruption (Vesuvius, Italy), doped with varying amounts of CaO and CaO + MgO. The compositions match the chemistry of melt inclusions and interstitial glasses from skarns at Vesuvius, which have been interpreted as related to mixing of magma with different amounts of CaO and MgO derived from the host carbonates (limestone and dolostone). Viscosity measurements were conducted at both high (1150-1400 degrees C) and low temperatures (640-760 degrees C) by concentric cylinder viscometry, differential scanning calorimetry, and micropenetration methods. Through an integrated approach which combines Brillouin and Raman spectroscopy with the aforementioned techniques, we accurately predict the viscosity changes induced by magma-carbonate interaction and identify the formation of nanoheterogeneities during low-temperature viscosity measurements. Notably, viscosity models from the literature fail to accurately reproduce our experimental data set at both high and low temperature. In the high-temperature regime, the addition of CaO induces a remarkable viscosity decrease, surpassing that produced by CaO + MgO addition. Furthermore, our findings reveal a significant viscosity/temperature crossover resulting from the addition of CaO and CaO + MgO to the melt phase. Undoped melt exhibits a higher viscosity compared to doped melts above 750 degrees C, with an inverse trend observed below this temperature threshold. Such rheological constraints may affect the mobility and mixing capability of melts exposed to different levels of carbonate assimilation.

Anthropogenic CO 2 from aerospace cabin, or CO 2 from outdoor atmosphere, such as the Martian atmosphere, may be converted into methane and water by the Sabatier reaction. Ru-based materials are suitable catalysts for methanation due to their high activity and selectivity. A previous study of a Ru/CeO 2 catalyst prepared by one-pot hydrothermal synthesis from metal nitrate solutions, showed good activity for CO 2 methanation with very high selectivity towards CH4 against CO (98 % at 350 °C), and high stability over time-on-stream, appearing as a promising and reliable Sabatier catalyst for in-situ resource utilization of CO 2 . In this study, four Ru/CeO 2 catalysts were synthesized by one-pot hydrothermal method starting from different metal ions precursors, such as ruthenium(III) chlorine or nitrosyl nitrate salts, and cerium(III) nitrate or ammonium cerium(IV) nitrate salts. The catalytic tests showed that the nature of the metal precursor strongly affects the catalytic performances of the Ru/CeO 2 system. The two catalysts prepared starting from RuCl 3 showed higher activity than those prepared from the most used Ru(NO)(NO 3 ) 3 precursor, whereas one formulation produced an inactive material. The time-on-stream test (TOS), carried out for 40 hours in the range of 300–500 °C, revealed no activity nor selectivity loss. To understand the effect of the precursor nature on the material, a deep physical-chemical characterization of samples is needed. Some preliminary results on the surface morphology and Ru reducibility and dispersion obtained by XRD, BET-BJH, H 2 -TPR and H 2 -TPD, RAMAN and XPS are reported.