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Observations of comet nuclei indicate that the main constituent is a mix of ice and refractory materials characterized by high porosity (70–75%) and low bulk strength (10−4–10−6 MPa); however, the nature and physical properties of these materials remain largely unknown. By combining surface inspection of comet 67P/Churyumov– Gerasimenko and three-dimensional (3D) modeling of the independent concentric sets of layers that make up the structure of its two lobes, we provide clues about the large-scale rheological behavior of the nucleus and the kinematics of the impact that originated it. Large folds in the layered structure indicate that the merging of the two cometesimals involved reciprocal motion with dextral strike–slip kinematics that bent the layers in the contact area without obliterating them. Widespread long cracks and the evidence of relevant mass loss in absence of large density variations within the comet’s body testify that large-scale deformation occurred in a brittle-plastic regime and was accommodated through folding and fracturing. Comparison of refined 3D geologic models of the lobes with triaxial ellipsoids that suitably represent the overall layers arrangement reveals characteristics that are consistent with an impact between two roughly ellipsoidal cometesimals that produced large-scale axial compression and transversal elongation. The observed features imply global transfer of impactrelated shortening into transversal strain. These elements delineate a model for the global rheology of cometesimals that could be possible evoking a prominent bonding action of ice and, to a minor extent, organics. [ABSTRACT FROM AUTHOR]

Geological maps of Earth typically incorporate field observations of rock lithology, structure, composition, and more. In contrast, conventional planetary geological maps are often made using primarily qualitative morphostratigraphic remote sensing observations of planetary surfaces. However, it is possible to define independent quantitative spectral units (SUs) of planetary surfaces, which potentially contain information about surface composition, grain size, and space weathering exposure. Here, we demonstrate a generic method to combine independently derived geomorphic and SUs, using the Rachmaninoff basin, Mercury, as an example to create a new geostratigraphic map. From this geostratigraphic map, we can infer some compositional differences within geomorphic units, which clarifies and elaborates on the geological evolution of the region. Plain Language Summary: Geological maps of rocks on Earth include information about what landforms the rocks exhibit, what they are made from, their orientation, and more. Many such details require ground observations, but these are generally not available for planetary geological maps, which rely on spacecraft data. Spacecraft images can be used to map planetary surface textures (geomorphology), but they can also be used to measure surfaces' responses to light (reflectance or emission spectra), which contain information about what the surface rocks are made from, their physical properties (e.g., grain size, roughness, porosity), and how long they have been exposed at the surface. We have combined earlier, independent geomorphic and spectral maps of the Rachmaninoff impact basin on Mercury to create a new "geostratigraphic" map that is more like a geological map that could be made of Earth. The new map highlights places that in the original geomorphic map would have been mapped all as a single unit, but are divisible based on spectral variations, attributable to differences in what the rocks are made from. This allows us to reconstruct a more detailed geological history of the region. Our method can be applied to other regions on Mercury and to other planetary surfaces. Key Points: We combine independent morphostratigraphic and spectral units of Rachmaninoff basin to create geostratigraphic unitsGeostratigraphic units can distinguish volcanic plains and impact melt in contact with each otherGeostratigraphic units imply a wider distribution of (LRM‐composition) impact melt than previously recognized [ABSTRACT FROM AUTHOR]

We present the first highly detailed morphological analysis of three craters located in Mercury's north pole, characterized by permanently shadowed regions (PSRs). This study, which began with an initial sample of 14 craters, highlighted three morphological classes, based on the craters' features: Complete complex morphology, Flat-floor morphology, and Immature complex morphology, presented here as maps of three representative craters, one for each class. As demonstrated by decades of studies, areas of PSRs within these craters could host water ice deposits, making them among the most interesting targets for future studies by the ESA/JAXA's BepiColombo mission. Our mapping work aims to give a cartographic context to subsequent chronological, thermal, and compositional analyses, as well as to provide a support to the acquisition strategy of the BepiColombo mission upon its arrival on Mercury in late 2025. The mapping highlights landforms which might be related to volcanic, gravitational, and maybe periglacial events. [ABSTRACT FROM AUTHOR]

Tidal exchange, capillary rise, water condensation-evaporation cycles, and crystallization of salts are the main causes of damage in historic brick buildings in Venice. The present study addressed these issues by proposing a study of twenty-three brick samples collected on the main façade of the Santa Maria dei Servi Church (14th century). The color, mineralogical composition, and texture of these samples were studied using standard methods such as spectrophotometry, X-ray powder diffraction (XRPD), optical microscopy (OM), and field emission scanning electron microscopy (FESEM). The presence of carbonates (calcite and dolomite) and newly formed silicate phases, such as gehlenite and diopside, provided indications of the temperatures reached during firing and suggested the absence of a good standardization in the production process. Meanwhile, XRPD and hyperspectral analysis (HA) detected sulfates (e.g., gypsum and mirabilite) as the main weathering products due to the salt decay process that affects monuments in the Venice lagoon environment. Moreover, secondary phases, such as Mg- and Ca-zeolites, occurred in bricks where the groundmass observed by OM was more vitrificated, and the XRPD patterns displayed the highest amorphous content. On-site mapping of sulfates and chlorophyll by HA was also performed on the main façade of the Church, highlighting the large presence of salts and biodeterioration. [ABSTRACT FROM AUTHOR]

This work highlights the importance of the Geogenic Radon Potential (GRP) component originated by degassing processes in fault zones. This Tectonically Enhanced Radon (TER) can increase radon concentration in soil gas and the inflow of radon in the buildings (Indoor Radon Concentrations, IRC). Although tectonically related radon enhancement is known in areas characterised by active faults, few studies have investigated radon migration processes in non-active fault zones. The Pusteria Valley (Bolzano, north-eastern Italy) represents an ideal geological setting to study the role of a non-seismic fault system in enhancing the geogenic radon. Here, most of the municipalities are characterised by high IRC. We performed soil gas surveys in three of these municipalities located along a wide section of the non-seismic Pusteria fault system characterised by a dense network of faults and fractures. Results highlight the presence of high Rn concentrations (up to 800 kBq·m−3) with anisotropic spatial patterns oriented along the main strike of the fault system. We calculated a Radon Activity Index (RAI) along north–south profiles across the Pusteria fault system and found that TER is linked to high fault geochemical activities. This evidence confirms that TER constitutes a significant component of GRP also along non-seismic faults. [ABSTRACT FROM AUTHOR]

S1094b is the largest (155 m-size) and southernmost known ice-exposing fresh crater discovered so far on Mars, revealing a relatively pure and unstable subsurface ice deposit located at the northern Martian mid-latitudes. In this work, we analyze HiRISE images taken on 27 February 2022 and on 5 December 2022 to perform a multi-temporal analysis of its ice-rich ejecta, combining this analysis with geologic mapping, the boulder size frequency distribution (SFD) and thermal modeling. The objective is to provide a multidisciplinary characterization of both the impact and subsequent exposed ice sublimation processes. The boulder SFD of both February and December cases show a power-law best fit with indices −4.68 ± 0.15 and − 3.47 ± 0.10, respectively. In the same timeframe, the density of boulders per km2 ≥ 1.5 m changes from 3908, to 596. This flattening is mainly due to the sublimation and consequent loss of the smaller-size icy boulders. This is confirmed by the ice volume computation performed on the area, which changed from ∼20,274 ± 3997 m3 to ∼7951 ± 1117 m3, i.e. a decrease of ∼60% in 274 Sols. The thermal models showed that the ice in this region is always unstable, leading to a total of 6504.71 sublimation hours from which we estimated a sublimation rate of ∼0.15 ± 0.04 mm/h (i.e. ∼3.60 ± 0.96 mm/Sol). The presence of this amount of accessible ice at such low latitudes could be a valuable resource for potential future human missions. • Conduction of multitemporal, multidisciplinary analyses on Martian crater S1094b. • Preparation of a geological mapping 5 geologic units and 4 landforms. • Observation of sublimation focusing on the smallest icy boulders loss. • Detection of the 60% water ice sublimation over 281 days. • Average sublimation rate detected at ∼1.96 m3/h or ∼ 0.15 ± 0.04 mm/h. [ABSTRACT FROM AUTHOR]

The Bressanone (Brixen) pluton, cropping out at the culmination of the Southalpine indenter between the North Giudicarie and the Pustertal-Gailtal faults, is mainly composed of Permian granodiorite to granite, with minor gabbros and diorites in its southern part. New U–Pb SHRIMP zircon ages reveal two distinct crystallization episodes at 289.7 ± 3.2 and 280 ± 2.2 Ma, respectively. The pluton is affected by a hydrothermal potassic to sodic + Cu metasomatic alteration, which has long been ascribed to a late phase of the Permian magmatism. In contrast with this hypothesis, we report new 39Ar–40Ar data for different generations of metasomatic K-feldspar, which indicate formation ages between 35.3 ± 0.3 and 27.8 ± 0.5 Ma. This interval overlaps with the ages of the widespread 'Periadriatic' calc-alkaline magmatism, which extends from the Western to the Eastern Alps straddling the Periadriatic Fault System. The observed hydrothermalism has geochemical characteristics compatible with those of the coeval calc-alkaline Periadriatic magmatism. These data altogether suggest the release of fluids from a hidden intrusion during the main stage of the Alpine orogenic magmatism. Our results provide the first evidence of Oligocene magmatic activity in the Southern Alps east of the Giudicarie Line, bridging the gap between the western-central and eastern Alpine magmatic plutons. A fairly continuous Oligocene magmatic belt straddling the Periadriatic Fault System is consistent with a triggering of the magmatism by slab steepening or slab break-off, either of which are considered to be an essential driver for the Miocene lithospheric rearrangement in the Eastern Alps. Our finding is particularly relevant given that the outcropping area of the Bressanone pluton is centred above the imaged subducting lithosphere gap that separates the Western-Central and the Eastern Alps, hence at a location where mantle upwelling should have been easier although no relevant magmatism was found to date. [ABSTRACT FROM AUTHOR]

• Quantification of the relation between grain-size and recession in carbonate rocks. • Improved understanding of the complexity of recession rate in carbonate rocks. • Definition of correction coefficients to be applied to known recession equations. • New methodological approach to estimating future stone deterioration in cultural heritage. In this study, the recession rate of eleven carbonate stones widely used in the cultural heritage of northeastern Italy and differing in their textural features and mineralogical composition was investigated. Samples of stones known as Vicenza (Nanto and Costozza varieties), Carrara marble, Verona (Red and Brown varieties), Asiago, Istria (Orsera variety), Aurisina, Chiampo (Ondagata and Paglierino varieties), and Botticino were subjected to accelerated ageing tests in an environmental test chamber for simulating the effect of rainfall, using two different water compositions corresponding to rainwater chemistry in the cities of Bologna (pH ∼ 7) and Stresa (pH ∼ 6) in Italy. Bulk stone recession was evaluated considering sample weight loss as a function of the number of wetting cycles. Moreover, direct measurements of recession were performed by confocal microscopy, which allowed 3D surface reconstruction of the stone surface and evaluation of differential recession as a function of calcite grain size. The results also allowed the definition of correction coefficients for calculating more precisely the recession rate of carbonate rocks using known recession equations from the literature. This pilot study illustrates a rapid and efficient methodological approach that can be used for providing reliable estimates of future stone deterioration in cultural heritage, related to specific environmental conditions and expected climate scenarios, which can be exploited for evaluating risk-based protection measures of a variety of historical artifacts and structures. [ABSTRACT FROM AUTHOR]

As a semi-enclosed crater basin on the northwest rim of Imbrium basin, Sinus Iridum is a key site to investigate the geological characteristics at the intersection of two basins. For this reason, we focused on model age determination in Sinus Iridum basin using Chang'E−2 high-resolution images coupled with compositional maps from the Clementine data sets, as well as with digital elevation models (DEMs) from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter (LRO). With these datasets we identified different geologic units onto which we performed model age determinations based on crater counting. This systematic analysis of the Sinus Iridum basin shows that the age of the oldest exposed basaltic unit is 3.37 ​Ga (Imbrian age), while the youngest, a mare basalt unit that enters the basin from Imbrium basin, is 1.24 ​Ga (late Eratosthenian). In general, the ages of the geologic units inside the Sinus Iridum basin gradually decrease from the northeast to the southwest, with the only exception of the young units being located in the north-eastern area. We conclude that the crater size-frequency distributions (CSFD) reflect a multi-layer sequence, suggesting multiple resurfacing events inside Sinus Iridum. The model age determinations identify several infilling events of basalts ranging from 3.37 ​Ga to 1.24 ​Ga, which are all derived mare basalt flows from the Imbrium basin. • Based on Chang'E-2 and Clementine data, a new geological map is produced for the Sinus Iridum basin. • The oldest geologic unit is 3.37 Ga, likely the age of the first common infillings of Sinus Iridum and Imbrium basins. • The youngest geologic unit is 1.24 Ga, and this layer's thickness (34.9m) is consistent with Yutu rover's result (35m). • The Sinus Iridum basin was deeply affected by the lava flows infilled from neighboring Imbrium basin in different periods. [ABSTRACT FROM AUTHOR]

Sinuous collapse chains and skylights in lunar and Martian volcanic regions have often been interpreted as collapsed lava tubes (also known as pyroducts). This hypothesis has fostered a forty years debate among planetary geologists trying to define if analogue volcano-speleogenetic processes acting on Earth could have created similar subsurface linear voids in extra-terrestrial volcanoes. On Earth lava tubes are well known thanks to speleological exploration and mapping in several shield volcanoes, with examples showing different genetic processes (inflation and overcrusting) and morphometric characters. On the Moon subsurface cavities have been inferred from several skylights in Maria smooth plains and corroborated using gravimetry and radar sounder, while on Mars several deep skylights have been identified on lava flows with striking similarities with terrestrial cases. Nonetheless, the literature on this topic is scattered and often presents inaccuracies in terminology and interpretation. A clear understanding of the potential morphologies and dimensions of Martian and lunar lava tubes remains elusive. Although it is still impossible to gather direct information on the interior of Martian and lunar lava tube candidates, scientists have the possibility to investigate their surface expression through the analysis of collapses and skylight morphology, morphometry and their arrangement, and compare these findings with terrestrial analogues. In this review the state of the art on terrestrial lava tubes is outlined in order to perform a morphological and morphometric comparison with lava tube candidate collapse chains on Mars and the Moon. By comparing literature and speleological data from terrestrial analogues and measuring lunar and Martian collapse chains on satellite images and digital terrain models (DTMs), this review sheds light on tube size, depth from surface, eccentricity and several other morphometric parameters among the three different planetary bodies. The dataset here presented indicates that Martian and lunar tubes are 1 to 3 orders of magnitude more voluminous than on Earth, and suggests that the same processes of inflation and overcrusting were active on Mars, while deep inflation and thermal entrenchment was the predominant mechanism of emplacement on the Moon. Even with these outstanding dimensions (with total volumes exceeding 1 billion of m3), lunar tubes remain well within the roof stability threshold. The analysis shows that aside of collapses triggered by impacts/tectonics, most of the lunar tubes could be intact, making the Moon an extraordinary target for subsurface exploration and potential settlement in the wide protected and stable environments of lava tubes. [ABSTRACT FROM AUTHOR]

The Curiosity rover's campaign in the Gale crater on Mars provides a large set of close-up images of sedimentary formations outcrops displaying a variety of diagenetic features such as light-toned veins, nodules and raised ridges. Through 2D and 3D analyses of Mastcam images we herein reconstruct the vein network of a sample area and estimated the stress field. Assessment of the spatial distribution of light-toned veins shows that the basin infillings, after burial and consolidation, experienced a sub-vertical compression and lateral extension coupled with fluid overpressure and cracking. Overall, rock failure and light-toned veins formations could have been generated by an overload produced by infilling material within the basin. [ABSTRACT FROM AUTHOR]

Radar observations from the Earth and multi-instrument measurements by MESSENGER mission have indicated the presence of large quantities of ices within the permanent shadowed regions (PSRs) located at Mercury poles. The detection and mapping of the distribution of volatile species on PSRs are among the primary scientific goals of the Spectrometer and IMagers for MPO Bepicolombo Integrated Observatory SYStem (SIMBIO-SYS) suite aboard ESA's BepiColombo mission. We report about a three-steps preparatory study mainly focusing on SIMBIO-SYS/Visible and near Infrared Hyperspectral Imager (VIHI) 0.4–2.0  μ m imaging spectrometer aiming (1) to render the solar illumination temporal evolution occurring on polar regions and in particular on Prokofiev and Kandinsky craters by studying the effects of shadows and penumbras caused by the finite apparent solar disc; (2) to simulate the spectral reflectance of various mixtures of average Mercury terrain and water ice in the spectral range of the VIHI imaging spectrometer channel in direct illumination, penumbra and shadowed illumination conditions; and (3) to verify the resulting VIHI signal-to-noise ratio during the different phases of the BepiColombo mission. [ABSTRACT FROM AUTHOR]

Complex patterns of normal faults with multiple orientations and/or highly curved shapes have been traditionally explained by successive tectonic phases of 2-dimensional deformation. Alternatively, multiple fault sets have been proposed to develop simultaneously and in orthorhombic symmetry during a single phase of 3-dimensional deformation. We use analogue models of normal faults to demonstrate that, without the influence of pre-existing structures, 3D extension is preferentially accommodated by the alternate, rather than simultaneous, development of faults with different trends. By means of stress-driven interactions, 3D deformation can be partitioned into coupled systems of normal faults, which display geometries commonly observed in tectonic settings affected by interacting plate boundaries. Under radial extension, deformation is accommodated by major curvilinear grabens coupled with minor perpendicular faults, resulting in the triple junctions of grabens observed in Afar. On the other hand, the alternate development of perpendicular faults accommodates synchronous bi-directional and mutually perpendicular extension, giving the same fault pattern observed in the Barents Sea rift-shear margin. [ABSTRACT FROM AUTHOR]

Abstract The investigation of the Martian surface through remote sensing allowed the identification of mound-like topographically positive features that, based on geomorphological observations, have been ascribed to different phenomena. New observations will be performed in the forthcoming future to look for possible methane sources, hence discriminating morphologically similar features is a key objective to efficiently investigate and target the Martian surface. Here, we performed fractal analysis on five Martian fields of mound-like features that have been interpreted respectively as mud volcanoes, pingos, tumuli, rootless cones and monogenetic volcanic vents successfully validating the major interpretations of these features and in turn, the applicability of the fractal clustering method for discriminating among such features. Indeed, this technique is able to assess if the analyzed features are directly related to underlying systems of connected percolating fracture networks and estimates their extension in the subsurface. Accordingly, volcanic vents and mud volcanoes appeared to be connected to percolating systems involving several kilometers of crust, pingos and tumuli resulted to be unequivocally unrelated to active percolating fractures while rootless cones outputted weak relationship with shallow active fracture systems. Highlights Through the development of this work we aim to provide the scientific community with an innovative tool for the planetary surfaces investigation. The successful outcomes herein presented can be summarized as follows: • The analysis of mounds' spatial distribution allows to spot percolating fracture networks • The method allows to locate the depth of the fluid source where present Such goals make possible: • The discrimination of morphologically convergent features on the surface • Tracing the fluid circulation in the subsurface [ABSTRACT FROM AUTHOR]

In this work, we analyze the ∼ 103 km-diameter Melkart impact crater on the surface of Ganymede, which is a ∼ 103 km impact crater located at the boundary between the two main geological units of the satellite, the light and dark terrains. Such crater is covered both by Galileo SSI and NIMS datasets allowing inference of any possible correlation between its geology and composition, as well as to investigate the evolution of the substrate units. We provide a geomorphological characterization of the crater by creating a high-resolution geological map, investigating the DTM and performing a strain analysis to infer its deformation. We find that the Melkart dome underwent strike-slip deformation with right-lateral kinematics. Moreover, this crater is a low strain end member with subtle deformation, which has been formed in an area of gradual transition between light and dark terrains. The results obtained through band depth and crystallinity maps of the study area do not reflect the evolutionary history of the crater, instead, they are representative of the different geological terrains affecting the subsurface of Melkart. Such result implies that the possible compositional differences between the crater's units might have been obliterated through time. Our analysis supports the interpretation that the material constituting the substrate of the crater might be heterogeneous suggesting that: (i) the transition between the two geological units might be gradual or ii) the dark material located over the study area only represents a thin layer draping the icy crust. • Analysis of a crater located at the boundary of Ganymede light and dark terrains. • High resolution geological map of Melkart impact crater on the surface of Ganymede. • Melkart is a low strain end member with subtle deformation from strain analysis. • The crater substrate material is heterogeneous from spectral analysis. [ABSTRACT FROM AUTHOR]

The Euganean Hills of North East Italy have long been recognised as an area characterized by a higher than average natural radiation background. This is due to two main reasons: a) primary lithogenic radiation due to rhyolitic and trachytic outcrops, which are "acidic alkaline" magmatic rocks potentially enriched in uranium and thorium; b) secondary sources related to a geothermal field e widely exploited for spa tourism in the area since the Roman age e producing surface release of radon-enriched fluids. Though radioactivity levels in the Euganean district have been often investigated in the past e including recent works aimed at assessing the radiation doses from radon and/or total gamma radiation e no effort has been put so far into producing a thorough assessment linking radiation protection data to geological-structural features (lithology, faults, water, organic matter content, etc.). This work represents the first part of the interdisciplinary project "Geological and geochemical control on Radon occurrence and natural radioactivity in the Euganean Hills district (North-Eastern Italy)", aimed at producing detailed results of the actual radiation levels in connection mainly with lithological parameters. A detailed sampling strategy, based on lithostratigraphy, petrology and mineralogy, has been adopted. The 151 rock samples collected were analyzed by high resolution g-ray spectrometry with ex situ HPGe detectors. Statistical and geostatistical analyses were performed, and outlier values of U and Th e possibly associated with anomalies in the geological formation e were identified. U, Th and K concentration maps were developed using both the entire database and then again after expunging the outliers; the two were then compared. In all maps the highest values can be associated to trachyte and rhyolite lithologies, and the lowest ones to sedimentary formations. The external dose due to natural radionuclides in the soil e the so called terrestrial gamma dose rate e has been calculated using the U, Th and K distribution measured in the bedrock samples. [ABSTRACT FROM AUTHOR]