Alessandro Pisello

Understanding how the glass/crystal ratio influences the spectral response of volcanic rocks is crucial for interpreting planetary remote sensing data. Here, four mafic rocks simulating a possible Martian composition were synthesized with identical bulk chemistry but different mineralogical assemblages, from fully amorphous to ∼70 wt.% crystal content, to investigate how crystal content affects Visible and Near‐Infrared (VNIR) reflectance spectra. Bi‐directional VNIR reflectance was collected at room temperature across a range of incidence (0°, 30°, 60°) and emergence (−70° to +70°) angles. The diagnostic absorptions of the two most abundant phases, pyroxene and glass, are not distinguishable in the spectra and can even reproduce the spectral fingerprint of olivine, absent from the samples; only minor iron oxides (magnetite and hematite, ∼1–7 wt.%) produce clearly identifiable absorptions. Instead, spectral slope emerges as the primary proxy for the glass/crystal ratio: NIR/VNIR slope decreases systematically with increasing crystal content, driven jointly by the incorporation of iron oxides and the loss of the positive‐slope contribution of residual glass. Principal Component Analysis and k‐means clustering independently confirm this control, identifying three clusters that map onto the glass/crystal ratio. This decoupling indicates that the crystal content of a mafic terrain cannot be inferred from pyroxene‐ or glass‐related absorptions alone, but rather from spectral slope and iron‐oxide features. These results experimentally support previous hypotheses linking the spectral diversity of Martian mafic terrains to their degree of crystal content and oxidation state and highlight variable glass abundance as an under‐considered contributor to the spectral interpretation of the Martian surface.

The PETRAS (Planetology, Exploration, Terrestrial Analogs, Robotics, Astrobiology, Spectroscopy) Summer School is an annual training program designed to provide early-career researchers with hands-on, multidisciplinary experience in planetary sciences. While primarily aimed at PhD students, the school is open to master's students, postdoctoral researchers, and, thanks to a collaboration with the DLR School Lab, also to high school students. This breadth of participation reflects a core ambition of PETRAS: to bring together all generations of scientists, from those with no research experience yet, to early-career researchers, to established professionals, creating a uniquely cross-generational learning environment.PETRAS is the result of a collaboration between multiple European research institutions and universities, including the University of Perugia, the Italian National Institute for Astrophysics, the Italian Space Agency, the German Aerospace Center, the German Research Center for Artificial Intelligence, the European Astrobiology Institute, and the University of Cologne, among others. This international network reflects the school's commitment to building bridges across national and institutional boundaries in planetary science training.The school takes place on Vulcano Island (Aeolian Islands, Italy), a natural laboratory offering direct access to active volcanic and hydrothermal environments that serve as planetary analogs. This field setting is central to the PETRAS philosophy: learning by doing, in environments that directly mirror the scientific questions being studied.The program combines thematic seminars, field activities, and hands-on workshops across six interconnected domains: volcanology and planetary geology, astrobiology and the study of extreme environments, remote sensing and spectroscopy, robotic exploration, geophysical methods, and drone-based geospatial mapping. Participants engage with topics ranging from Venus and Mars surface geology to the search for biosignatures in hydrothermal systems, from Raman spectroscopy interpretation to autonomous navigation in planetary analog terrains. Field activities include volcanological excursions on La Fossa crater, environmental sampling for astrobiological analysis, in-situ spectroscopic mineral detection, geophysical subsurface imaging, and drone flight demonstrations. Evening sessions extend the learning experience with astrophotography workshops and stargazing.PETRAS is offered free of charge to all selected participants, with accommodation costs kept to a minimum through institutional agreements. This model is specifically designed to lower financial barriers to participation, welcoming students and researchers from institutions with limited funding. The selection process prioritizes scientific motivation and potential over institutional affiliation, drawing participants from across Europe and beyond.Now in its third edition in 2026, PETRAS builds on the legacy of the Vulcano International Summer School, active since 2015 under successive funding frameworks including ROBEX, Europlanet, and ARCHES. The school has been supported over the years by a range of institutions: in 2024 by the European Astrobiology Institute (EAI); in 2025 by the Italian National Institute for Astrophysics (INAF) and the European Space Agency (ESA); and in 2026 by INAF, Europlanet, and the Italian Society of Planetary Sciences (SISP). By combining scientific depth with an accessible, field-based format and a strong international network, PETRAS exemplifies how targeted training initiatives can support capacity building, foster collaboration, and create inclusive pathways into planetary science across all career stages.

Introduction: The most common type of rock present ont he surface of terrestrial planets in the Solar System are volcanic-magmatic rocks, which are constituted by lava flows and fragmented pyroclasts whose texture presents both glassy and crystalline silicate phases.Planet Mars is, besides the Earth, the most diverse terrestrial planet in the Solar System, presenting magmatic rocks with compositions ranging from ultramafic/basaltic to alkaline/trachy-andesitic [1].Understanding the influence that chemical composition and different phases (both crystalline and amorphous) have on the spectral response of volcanic rocks is pivotal to interpret remotely sensed spectra that are commonly used to interpret the geology of terrestrial planets. Thus, we synthesized Martian simulants with two putative Martian compositions, on which we performed cooling experiments together with a rheological, mineralogical and spectral characterization in order to provide reference to interpret the geological processes that have occurred on Mars.Methods:Samples were created by mixing powdered oxides to mimic the composition (Table 1) of volcanic products from Gusev and Gale craters, as they were hypothesized from data belonging to different missions [1].Table 1: Composition of the starting materials accounted GusevGaleSiO247.3352.04TiO20.570.66Al2O311.1915.83FeO19.1210.89MnO0.420.18MgO10.294.44CaO8.176.76Na2O2.767.06K2O0.142.14 The powders were molten at 1450°C to form a silicate melt, which were then quickly cooled to produce glasses. Then, for each of the produced glasses three cooling experiments were conducted in a Gero HTRV 70-250/18, equipped with Anton Paar rheometer [see 2 for reference]. Powdered glass was brought to superliqidus temperature and, after having reached the equilibrium, it was cooled down at a 100°C/h rate to crystallize. Crystallization was monitored through the measurement of viscosity during cooling, so that thre phases were individuated and samples: the point at which crystals start nucleating, the point at which crystal were grown and a final point of advanced crystallization where viscosity was not measurable anymore due to extreme rigidity of the samples (see arrows in Fig. 1).Figure 1: Example of Viscosity path duting cooling for Gale simulant. Arrows indicate stages at which experiments were stopped.The synthesized samples were analyzed using X-ray powder diffraction (XRPD), and quantitative phase analysis (QPA) was performed using the Rietveld profile fitting method with internal standards to determine amorphous content.Spectral analyses: Reflectance spectra were collected at the Cold Surface Spectroscopy (CSS) facility (https://cold-spectro.sshade.eu) located at the Institut de Pla-nétologie et d'Astrophysique (IPAG), Grenoble, France. The instrument used was the SHINE Spec-tro-Gonio Radiometer. The instrument is equipped with a cryogenic simulation chamber, CarboN-IR, to control the temperature of the samples. Spectra were collected in the 1-4.2 μm spectral range at different low temperatures between 105 and 290 K. The sample is cooled to a given temperature and then held for about 5–10 min to wait for thermal equilibrium and then during the measurement time, about 65–80 min depending on some acquisition parameters. We kept each sample for 70–90 min at a given temperature before starting our measurements.Future perspectives:Spectral characterization at low temperature is currently ungoing and will shed light on the influence of temperature on the detection of silicate phases. Preliminary spectral investigations suggest us that for samples with identical bulk chemical composition but different mineralogical assemblage, the spectral response within Visible and Near InfraRed (VNIR) and mid-infrared (MIR) is deeply different. VNIR spectra are influenced by the nucleation of iron-related phases whereas MIR spectra are dependant on Si-bearing phases. The mechanism influencing the shape of spectra results in fact from a complex interaction of the spectral response of different mineral/amorphous phases. In this way, the shape is easily misinterpreted as the features of the different phases which are often no longer recognizable. A thorough analysis helped us to understand which are the features that can be accounted for the interpretation of this kind of igneous materials, but a more comprehensive study on different compositions is needed for a complete assessment of this approach.References:[1] McSween Jr, H. Y. (2015). Petrology on mars. American Mineralogist, 100(11-12), 2380-2395.[2] Vetere, F., Petrelli, M., Perugini, D., Haselbach, S., Morgavi, D., Pisello, A., ... & Holtz, F. (2021). Rheological evolution of eruptible Basaltic-Andesite Magmas under dynamic conditions: The importance of plagioclase growth rates. Journal of Volcanology and Geothermal Research, 420, 107411.Additional Information: This work was carried on thanks to ASI-UniPG agreement 2019-2-HH.0 and in the framework of Trans-National Access research project selected and funded by Europlanet-2024 RI (European Union’s Horizon 2020 RI under grant agreement No. 871149). We also acknowledge the support from MUR in the framework of SUPER-C, ‘Dipartimento di Eccellenza 2023-2027’.

The physical behaviour of silicate magmas and their eruptive style are strongly controlled by melt structure, volatile content, and cooling conditions, reflected in spectral properties. Magma rheology and eruptive style are primarily controlled by volatile-driven modifications of melt structure (especially due to H₂O), which govern fragmentation during magma–water interactions, producing fine, lithic-rich tephra. Spectroscopic techniques provide a powerful means to investigate melt structure and pre-eruptive volatile contents, offering insights into eruption dynamics.We analysed tephra samples from two phreatomagmatic successions on Vulcano Island (Aeolian Arc, Italy), a natural laboratory to investigate relationships among magma composition, volatile content, and eruption style (Keller, 1980; De Astis et al., 1997). Eleven ash-rich layers were sampled. Field measurements included VNIR reflectance spectra acquired with an ASD FieldSpec spectroradiometer and portable Raman spectroscopy. Diffuse reflectance FTIR spectra were collected using a Bruker Invenio X spectrometer on natural and oven-dried samples (105 °C, 48 h) to evaluate adsorbed water. Quantitative spectral parameters were extracted, including band center, full width at half maximum, and area under the curve in the 300–25000 nm domain. We investigate whether VNIR reflectance spectroscopy and laboratory FTIR measurements can identify spectral criteria diagnostic of eruption style in surge-dominated pyroclastic deposits. Preliminary analyses reveal systematic spectral variations related to volatile content and silicate melt structure. The spectra display absorption features attributed to Fe³⁺, molecular H₂O, OH⁻, Al–OH, and Fe–OH vibrations, enabling extraction of band parameters sensitive to hydration state and polymerization degree. Thermal treatment experiments show reduced band areas and spectral slope associated with H₂O and OH⁻ absorptions after heating, indicating that most water in natural samples is weakly bound or adsorbed. However, water loss varies among stratigraphic levels, reflecting differences in glass content, porosity, and hydration history. Variations in Si–O and Al–O band positions and widths indicate differences in silicate network polymerization, with narrower bands and shifts toward higher wavenumbers consistent with evolved compositions. Overall, the spectral signatures are consistent with highly explosive eruptions involving water-rich, evolved magmas and record internal heterogeneity within the eruptive column, marked by progressive degassing during the eruptive event.This study contributes to the development of spectral reference datasets of terrestrial volcanic materials, essential for interpreting remote sensing data. By linking spectral features to the physical and chemical characteristics of volcanic deposits and their eruptive context, we constrain the nature of volcanic activity on other planetary bodies.De Astis, G.F. et al., 1997. Volcanological and petrological evolution of the Vulcano Is land Aeolian arc, southern Tyrrhenian Sea. J. Geophys. Res. 102, 8021–8050.Keller, J., The island of Vulcano, Rend. Soc. Ital. Mineral. Petrogr., 36, 369–414, 198

Magmatism and volcanism are key processes that shaped the surface of rocky planets in the Solar System, and understanding how magmatism occurred on these planets is essential to reconstruct their geological histories. It is very likely that volcanic terrains on planetary surfaces are covered by products that have a porphyric, aphanitic or hyalocrystalline texture, in which crystalline phases represent only a fraction of the rocks that are mainly composed by amorphous materials such as glasses.Remote investigation of planetary surfaces combines geomorphological analysis with spectral data. Regarding the latter, the interpretation of spectral information from planetary terrains needs to be based on the comparison with reference material.Up to now, libraries and repositories are mostly report information about so-called planetary analogues consisting of crystalline materials rather than amorphous products. This happens because of the lack of spectral features of amorphous products. However, a the presence of amorphous material together with crystalline phases deeply influence the spectral response of the latter [1].For this reason, the Petro-Volcanology Research Group at the University of Perugia started to build up a spectral database of volcanic rocks, both natural and synthetic, to understand how and how much are crystalline and amorphous products influencing each other in determining the spectral response of a rock/terrain. In this work we report the spectral characterization of various products within two ranges: Visible and Near Infrared (VNIR) and Mid-Infrared (MIR).The accounted products consist of:- Synthetic silicate glasses with wide range of chemical composition [2,3]- Synthetic planetary analogues consisting of rocky materials containing both amorphous and crystalline products [4]- Natural volcanic rocksThe overall analysis of the spectral response shows that, within the MIR, it is relatively easy to link the wavelength position of well-known spectral features (Christiansen feature, Reststrahlen Bands, Transparency features) to the silica content of the product itself, no matter which crystalline phases are present within the rock. This finding is of pivotal importance since the determination of silica content is fundamental for a characterization of volcanic products.On the other hand, investigations and analyses on VNIR spectra show that the interpretation within such is more complicated. Indeed, a small presence of Iron-bearing crystals can deeply influence the VNIR spectrum. However, some constrains can be build using empirical parameters and machine-learning approaches.All the spectra produced and published by our research group is or will be made available to everyone, open-source, within the platform hosted by ASI-SSDC (www.ssdc.asi.it/rockspectra/), making it possible for scientist from all-over the world to integrate such data in other researches or to directly compare planetary spectra to laboratory data [4].[1] Horgan, B. H., Cloutis, E. A., Mann, P., & Bell III, J. F. (2014). Near-infrared spectra of ferrous mineral mixtures and methods for their identification in planetary surface spectra. Icarus, 234, 132-154.[2] Pisello, A., Ferrari, M., De Angelis, S., Vetere, F. P., Porreca, M., Stefani, S., & Perugini, D. (2022). Reflectance of silicate glasses in the mid-infrared region (MIR): Implications for planetary research. Icarus, 388, 115222.[3] Pisello, A., De Angelis, S., Ferrari, M., Porreca, M., Vetere, F. P., Behrens, H., ... & Perugini, D. (2022). Visible and near-InfraRed (VNIR) reflectance of silicate glasses: Characterization of a featureless spectrum and implications for planetary geology. Icarus, 374, 114801.[4] Pisello, A., Zinzi, A., Bisolfati, M., Porreca, M., & Perugini, D. (2022). A new spectral database for silicate glasses: a fundamental resource to interpret characteristics of volcanic terrains on planetary bodies (No. EPSC2022-539). Copernicus Meetings.

Introduction: Volcanic and magmatic processes shaped the surfaces and contributed to the mineral diversity of Mercury. Beyond the ubiquitous presence of effusive products (smooth plains) explosive volcanism is suggested by the presence of depressions surrounded by high-reflectance halos, interpreted as eruptive centers, as well as calderas and vents linked to impact structures or faults [1]. BepiColombo hosts SIMBIO-SYS and MERTIS, two instruments that will characterize the surface of Mercury with different methodologies:SIMBIO-SYS (Spectrometer and Imagers for MPO BepiColombo Integrated Observatory System) is a system for imaging and spectroscopic analysis. Its goals are to study surface geology, volcanism, tectonics, age, composition, and geophysics. One of the systems of SIMBIO-SYS is the Visible Infrared Hyperspectral Imager Channel (VIHI), which performs hyperspectral imaging to map the planet's mineralogical composition in the Visible and Near Infrared (VNIR) range [2].MERTIS (MErcury Radiometer and Thermal Infrared Spectrometer) aims to provide detailed mineralogical information about Mercury’s surface by globally mapping spectral emittance with high spectral resolution. Operating in the 7-14 µm wavelength range with high spectral resolution, MERTIS can detect key surface features like the Christiansen feature (CF), Reststrahlen bands (RB), and Transparency features (TF) [3].The interpretation of spectral data from these instruments needs to be based on the spectral response of the reference material. This is complicated by factors such as mineral composition, elemental abundance, temperature, surface roughness, and particle size, which all contribute to spectral response. This study aims to explore the VNIR and MIR spectral response with the goal of building a comprehensive database of Mercury-like silicate glasses to support future spectral interpretations of Mercury's surface, where volcaniclastic materials are thought to be abundant. NVP NVP_Na NVP_Mg SiO2 58.09 55.89 53.85 TiO2 0.98 0.90 0.90 Al2O3 15.54 15.11 12.44 FeO 2.93 3.36 3.34 MgO 16.82 13.80 22.76 CaO 5.04 4.36 6.35 Na2O 0.30 6.35 0.16 K2O 0.32 0.22 0.19 Table 1: The compositions of three starting materials prepared for this study, taken from [4].Methods:Material preparation: Three compositions resembling that of the Northern Volcanic Plains (NVP) on Mercury were chosen: an iron-poor potassium-rich composition resembling the composition of NVP [4] the same one with an addition of Na (NVP_Na), and another with an addition of Mg (NVP_Mg) (Table 1). From these compositions, glasses were reproduced following the procedure illustrated in [6]. Glasses were ground and sieved into grain size fractions: 0–25 µm, 25–38 µm, 38–63 µm, 63–106 µm, 106–150 µm. From these, also Gaussian-like distributions of powders were produced, characterized by mean values of 30, 80, and 120 µm, and standard deviations of 20 and 40 µm.Spectral Analyses: Spectroscopic analysis was performed using a FT-IR apparatus consists of a Bruker Invenio-X spectrometer coupled with Harrick Praying Mantis™ for Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). Samples were measured in atmosphere and corrected to a background measured with a mirror. To focus on SIMBIO-SYS and MERTIS spectral range, we present the spectra in the wavelength ranges 0.4-2µm and 7 to 14 µm.Results and perspectives:VNIR: the spectral shape of all samples is characterized by a generally positive slope and a prominent absorption at ca 1.1 µm, and a second, very weak, absorption at ca. 1.9 µm. These features are the usual ones observed for silicate glasses [5] and are linked to the presence of Fe-O bonds, which are not detectable in iron-free samples.MIR: shape of spectra in this spectral range is influenced by both chemical and granulometric characteristics. First, it is linked to the connectivity rate of the silicate structure consisting of tetrahedral units T, primarily Si, Al, and Ti, namely by the amount of bridging oxygens (BO). Moreover, the vibrations in T-O bonds occur at different wavelengths depending on the number of BO between two Si-tetrahedra (BO) and therefore on the amount of Si, Al and Ti present in the structure [6]. In our set of spectra, local maxima at 10 µm detectable for all spectra can be correlated to T-O bonds and can be assigned to RB feature. All spectra show a local negative peak at ∼8 μm that can be recognized as the CF, a local minimum which appears on both amorphous and crystalline materials, and that is often used as a diagnostic feature for igneous products. Moreover, the presence of fine material produces the presence of TF at ca. 12 μm, occurring when a large surface/volume ratio determines a larger ratio of scattered/absorbed light. Only the spectra related to the finest products show such a feature, reasonably, in our set of spectra.All these spectra will be made available on the SSDC-ASI portal of the PVRG group [7, https://www.ssdc.asi.it/rockspectra/], and the use of these spectra as reference material will be pivotal for the interpretation with data acquired by the instrument onboard the BepiColombo mission such as SIMBIO-SYS and MERTIS. Ongoing parametrization and analyses on these data will also provide models for the identification of putatively unknown igneous materials on Mercury.References:[1] https://doi.org/10.1002/jgre.20075[2] https://doi.org/10.1007/s11214-020-00704-8[3] https://doi.org/10.1007/s11214-020-00732-4[4] https://doi.org/10.1002/2015JE004792[5] https://doi.org/10.1016/j.icarus.2021.114801[6] https://doi.org/10.1016/j.icarus.2022.115222[7] https://doi.org/10.5194/epsc2022-539Additional Information: We acknowledge ASI-UniPG agreement 2019-2-HH.0. Part of this work was supported by the Ministero dell’Istruzione dell’Università e della Ricerca (MUR) through the...

Remotely sensed hyperspectral data provide essential information on the composition of rocks on planetary surfaces. On Mars, these data types are provided by the CRISM instrument (Compact Reconnaissance Imaging Spectrometer for Mars) [1], a hyperspectral camera that operated onboard the MRO (Mars Reconnaissance Orbiter) probe that collected more than 10 Tb of data. CRISM covers a spectral range going from ca. 400 to ca. 4000 nm, with a spectral resolution of 6.55 nm/channel and a spatial resolution of up to 18.4 m/px. The most advanced CRISM data products are the MTRDRs (Map-Projected Target Reduced Data Records) [2]. These data are re-projected onto the Martian surface and are cleaned from the so-called ”bad bands” (noisy stripes).The two main CRISM MTRDR subproducts are the hyperspectral datacube and the spectral parameter datacube. The first contains the detected reflectance spectra, while the second is composed of 60 different spectral parameters, as defined in [3], usually to produce RGB maps emphasizing specific minerals within the scene. Usually, the creation of the RGB maps and the spectral analysis are conducted using commercial software like ENVI©, which are usually not specifically meant for these dataset, inherently implies some costs for the user, and does not always meet some of the fundamentals principles of Open Science [4].Here we present a free open-source tool completely written in Python called pyFRESCO (Flexible RGB Extraction and Spectra Comparison for Observations), which allows the use of CRISM MTRDR data. The software can create RGB maps and select Regions Of Interest (ROI) from which the user can extract and further analyze the spectral data available from the chosen CRISM scene.The possible types of analysis that pyFRESCO supports range from simple descriptive statistics (to obtain, for example, mean spectra of a ROI), and spectra-related pre-processing methods like continuum removal and/or smoothing, to analysis through more complex techniques. One of those techniques being a direct spectral comparison tool that, given a guess taken from the minerals that are present in the MICA files [5], infer the nearest absorption features to the tabulated ones. Another technique, applicable only to mafic minerals, is the calculation of band parameters given in [6] for mafic mineral discrimination (e.g. between pyroxenes and silicate glasses). The last one involves a machine learning driven Modified Gaussian Model [7] for spectral unmixing with either skewed or non-skewed normal distributions.Moreover, with pyFRESCO it is possible to georeference the RGB maps to export them to ArcGIS©/QGIS software.In support of the effectiveness of pyFRESCO, we present a case study conducted on the CRISM target FRT00009B5A that covers the northern portion of Kai crater, located in Meridiani Planum. The choice of this particular case study is motivated by the morphological and compositional complexity shown by this specific target [8], demonstrating that pyFRESCO can be useful especially in complex scenarios that require a detailed analysis of the geological context, evolution, and processes. Bibliography:[1] Murchie, S. 2007. doi:10.1029/2006JE002682.[2] Seelos, F.P. 2016. URL: https://api.semanticscholar.org/CorpusID:217998642[3] Viviano-Beck, C.E. 2014. doi:10.1002/2014JE004627.[4] Barker, M. 2022. doi:10.1038/s41597-022-01710-x.[5] Viviano-Beck, C. E., 2015. URL: https://crismtypespectra.rsl.wustl.edu/.[6] Horgan, B.H. 2014. doi:https://doi.org/10.1016/j.icarus.2014.02.031.[7] Sunshine, J.M. 1990. URL: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JB095iB05p06955[8] Baschetti, B. 2025. doi: https://doi.org/10.1029/2024JE008564

Volcanic and magmatic processes have played a significant role in shaping Mercury’s surface and contributing to its mineral diversity. Areas such as smooth plains, which cover 27% of the planet, are thought to have formed from effusive volcanic events. Explosive volcanism is also suggested by the presence of depressions surrounded by high-reflectance halos, calderas, and vents linked to impact structures or faults. The BepiColombo mission, a collaboration between ESA and JAXA, was launched in 2018 to explore Mercury. It consists of two orbiters, MIO (JAXA) and MPO (ESA), with a focus on studying the planet's interior, surface, exosphere, and magnetosphere. The MPO carries instruments such as SIMBIO-SYS and MERTIS, which are designed to acquire spectral data.Interpreting planetary surface data often requires understanding complex factors like mineral composition, elemental abundance, temperature, and particle size. This study investigates the mid-infrared (MIR) spectral response of silicate glasses with a range of grain sizes and chemical compositions, aiming to build a database to support future spectral analyses of Mercury’s surface, where volcaniclastic materials are expected to be abundant.Three compositions resembling the Northern Volcanic Plains (NVP) on Mercury were prepared: NVP, NVP_Na, and NVP_Mg, each with varying amounts of Na and Mg. These compositions were created by melting pure oxides at 1400°C, then crushing the resulting glass into powder and re-melting it to ensure homogeneity. The glass was sieved into various grain size fractions, with some samples mixed to create new samples with Gaussian-like distributions to explore how fine-grained fractions affect spectral responses, particularly in relation to volcanic ash.Spectroscopic analysis was performed using a Bruker Invenio-X FT-IR spectrometer. The VNIR spectra (400-2000 nm) showed typical features of silicate glasses, with an absorption peak at around 1100 nm and a weaker one at 1900 nm, related to Fe-O bonds. The slope of the spectra did not vary much with increasing grain size in NVP samples, but there was a noticeable increase in the NIR slope (1200-1800 nm) for NVP_Na and NVP_Mg.In the MIR region (7-14 µm), the spectra revealed a correlation between the shape of the spectra and the chemical and granulometric characteristics of the samples. A local maximum at 10000 nm was observed for all spectra, associated with tetrahedral silicate units, and the NVP_Mg spectra showed distinct features due to the network-modifying role of Mg. The spectra also exhibited the Christiansen Feature at around 8 µm, a diagnostic feature for igneous products, and a transparency feature around 12 µm, which appeared in spectra of finer-grained samples.These spectra will be made available on the SSDC-ASI portal and will be crucial for interpreting data from the BepiColombo mission, particularly from SIMBIO-SYS and MERTIS. This research will help in identifying potential unknown igneous materials on Mercury’s surface.

Silicates are the main constituent of volcanic terrains on terrestrial planets in the Solar system. On Earth, we know that volcanic terrains are constituted by lava flows and fragmented pyroclasts whose texture presents both glassy and crystalline phases. Understanding the influence of glass/crystal ratio on the spectral response of volcanic rocks is therefore focal to interpret remotely sensed spectra that are commonly used to interpret the geology of terrestrial planets. Thus, we performed spectral characterization of lab-made mafic volcanic products which were synthesized in the PVRG labs with the aim to present different degrees of crystallinity.Samples were synthesized by mixing and melting oxides to resemble the composition of a Nakhlite meteorite. First we produced a homogeneous silicate glass (Nglass) which was then used to prepare three more samples by melting at 1500°C and then cooling down slowly (52-56 °C per hour) towards subliquidus temperatures of ca. 1200°C (N12), 1100°C (N11), and 1000°C (N10), respectively. Each sample stayed for 48 hours at the target temperature and was finally quenched in air.SEM and XRPD analyses and Rietveld method quantitative phase analyses were performed to assess type and degree of crystallinity, showing how N11 and N10 present a similar mineralogical assemblage with ca. 30% of glass and crystal species including augite, magnetite, cristobalite and other minor phases similar to the mineralogical composition of a natural Nakhlite. Sample N12 presents less diverse mineralogy (augite and magnetite) and ca. 70% of glass. Bi-directional reflectance spectra was collected at room temperature in the 1-4.2 µm range considering a set of 3 incidence angles (i = 0°; 30°; 60°) and emergence (e) angles between -70° and 70° using the custom-made bidirectional reflectance spectro-goniometers SHINE at the Cold Surface Spectroscopy facility (CSS) of the IPAG laboratory in the frame of the Trans-National Access program, project number 21-EPN-FT1-025, of Europlanet 2024.Spectral analyses show how, in the Visible and Near-Infrared, increasing crystallinity causes slopes of spectra to gradually shifts from positive for glasses towards flat-negative for crystalline material. The spectral features of the single mineral phases are barely distinguishable for N10 and N11, where spectra are flattened probably because of the presence of magnetite, whereas the spectral signature of Fe in augite is distinguishable for N12 located at ~0.9 and ~1.15 µm.Changing observation geometry, reflectance values and spectral slope show important variations while the bands position remains unchanged. We observe important dependence of band and slope in correspondence of low phase (< 30°) angle and high phase angle (> 100°).To identify distinctive features we used principal component analysis (PCA) obtaining four clusters in the PC space which are relatable to the four samples. K-means clustering was used to verify our clustering obtaining a very low level of misclassification, especially regarding Nglass.These results provide further information on the spectral response of synthesized rock samples, especially for what concerns glass-bearing materials, that can be used for modeling of spectral information coming from volcanic rocky bodies in the Solar system.