Search

Thanks to the VIR spectrometer onboard NASA’s Dawn spacecraft, which orbited Vesta in 2011–2012, thousands of hyperspectral images of its surface have been collected. The mission confirmed the HED (Howardite–Eucrite–Diogenite) meteorite composition of Vesta. Moreover, the VIR spectrometer detected the 2.8 µm absorption band, due to the presence of the OH molecule. In this work, we took advantage of the newly calibrated data of the VIR spectrometer by characterizing new spectral features thanks to the improved signal-to-noise (S/N) ratio for these spectra. The main goals of this work are as follows: (1) to characterize Vesta’s surface in the visible range and (2) to confirm, reinforce and characterize the OH distribution on Vesta by studying the 2.8 µm band and looking for OH combination bands around 2.2–2.4 µm. A possible relation between the 1.9 µm absorption band due to the presence of pyroxenes and the one at 0.5 µm was analyzed. Finally, the analysis of hydroxyl absorption bands evidenced an anti-correlation between the abundance of hydroxyl-bearing molecules and the surface reflectance. This confirms that the hydroxyl presence is linked to the dark units on Vesta.

The distribution of water in differentiated Solar System bodies depends on many factors including size, distance from the Sun, and how they incorporated water. Most of this water is likely locked as hydrogen in mantle minerals and could amount to several Earth oceans worth in mass for the largest planets. An essential compound for the development of life, water also has a tremendous influence on planetary evolution and volcanism. Only Earth has an active exchange of water between surface and mantle. Surface water on other differentiated bodies mostly results from degassing by volcanoes whose mantle sources are inherited from magma ocean processes early in their history. Airless bodies also acquire surface water by impacts, spallation, and from the solar wind.

Introduction. Oxia Planum is the selected landing site of the ExoMars mission [1]. A drilling system is installed on the ExoMars rover, able to analyze down two meters in the subsurface of Mars. Among the scientific objectives of the ExoMars mission, the searching of the organics or volatiles species plays an important role. The Ma_Miss spectrometer (Mars Multispectral Imager for Subsurface) [2] will investigate the borehole generated by the drill and it will be able to characterize and map the presence of possible ices. In this work we developed a numerical model to predict the subsurface temperatures after the heat released by the drilling operations. The increase in temperature due to the drilling operations, in fact, could affect the survivor of the volatile species [3]. Here we report the results about subsurface temperature of Oxia Planum. Numerical modeling We developed a numerical modeling to predict the subsurface temperature of Oxia Planum. In the subsurface we solve the classical heat equation [3]: where ρ is the density, c p the specific heat, K the thermal conductivity and T the temperature. Heat transfer occurs only by conduction since convection is negligible due to the small temperature gradients involved as well as the characteristic size of the sample. At the top we imposed a radiation boundary condition. In order to take into account the heat released by the drilling operations we imposed a frictional heating flux on the sides “in contact” with the drill (the lateral sides of the borehole of Fig.1). This flux is defined by the equation [3]: where η is the coefficient of friction, Fn the thrust, ω the rotational velocity, r the radius of the hole and h the height of the domain of integration (in our case 50 cm). The parameters adopted in this work are F n = 300 N, rpm = 30 or 60, η = 0.3 or 0.9, tip density = 3500 kg m-3, tip thermal conductivity = 540 W m-1K-1, tip specific heat = 790 J kg-1K-1 and a drilling window of 90 min, characterized by 30 min in “on mode”, followed by 30 min in "off mode” and finally 30 min in “on mode”. The surface and subsurface of Oxia Planum is characterized by a thermal inertia of 650 TIU, with an initial temperature fixed to 200 K. Some assumptions are made: I) instantaneous drilling(drill excavation is not modeled); 2) constant thrust; 3) constant rotational velocity. Fig.1: Geometry adopted in this work. The borehole of the drilling system is represented by the cylinder embedded in this domain of integration, with a radius of 13 mm (the thickness of the drill tip). In Fig.2 we report an example of 1-D temperature profile at z=50 cm (the maximum depth of the borehole). In the x-axis we report the distance from the hole, where shadowed red rectangle identifies the drill (or equivalently the borehole). Top panel of Fig.2 is characterized by rpm=30 and η=0.3 while the bottom panel by rpm=30 and η = 0.9. From these plots we note a difference, in the maximum value after 90 minutes, of about 40 K in favour of the case with η=0.9. The increase in temperature due to the drilling operations, in case of η=0.9, respect the initial assumed value (200 K) is about 80 K. The initial value of 200 K is chosen since is close to the surface equilibrium temperature value for Mars. As in [4] we can calculate the lifetime of an ice spherical deposit of mass m0, with a radius equal to the radius of the drill tip. The relative loss of ice mass at time (t) after the deposit is raised the temperature T is: where t is the time expressed in seconds. In this equation, Г represent the water rate emission, rp the radius of the tip and рice the density of the ice. By using the maximum sublimation rate, we obtain in case of rpm = 30 and η=0.3 a loss of about 60% of the initial mass, while in case η=0.9 of the loss is complete. In Fig.2 we report an example of temperature internal profile after the heat released by the drilling operations. Both panels refer to rpm=30: top panel is characterized by η=0.3 while bottom panel by η=0.9. Summary and Conclusions. We simulated the heat released by the drilling operations in different case of friction (η) and rotatonal speed (rpm) of the drill. We observed that in case of η=0.3 the maximum temperature increase at a depth of 50 cm is about 55 K (with rpm=30) and about 75 K (with rpm=60), while in case of η=0.9, the maximum temperature increase becomes 90 K (with rpm=30) and 130 K (with rpm=60) [3]. We also calculated the sublimation rate and the lifetime of a hypothetical spherical ice-rich deposit, with a radius equal to the size of the tip of the drill. We obtained that, after 90 minutes from the start of our simulations, in the coldest scenario (η=0.3 and rpm=30) the remaining initial mass is about the 60%, while in the other scenarios we have a complete loss of the mass [3]. Future improvements in the numerical model (e.g. a complete treatment of the diffusion of volatiles) as well as validation with laboratory experiments will be made. Acknowledgments. This work is funded and supported by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2017-48-H.0].References [1] Vago J.L. et al. 2017; [2] De Sanctis M.C. et al 2017; [3] Formisano M. et al. 2021; [4] Andreas E.L. 2007; [5] Coradini A. et al. 2001

Introduction We developed a simple model to simulate Ma_MISS data acquisition and visualization and to support the development of acquisition strategies. The Ma_MISS instrument Ma_MISS (Mars Multispectral Imager for Subsurface Studies) is the miniaturized VNIR spectrometer embedded in the drill system of the ExoMars rover[1]. Ma_MISS will perform spectral reflectance measurements inside holes drilled into the surface of Mars up to a depth of 2 m. It will characterize the mineralogy and stratigraphy of the borehole walls and will allow the in-situ study of the subsurface environment, before any samples are collected and extracted. Taking advantage of the finely controllable drill tool motion, Ma_MISS can map the borehole walls. In addition to single point acquisitions, Ma_MISS can also be programmed to acquire “Ring” and “Column” scans, where the spectrometric acquisitions are interleaved with step rotations or translations of the drill tool. Borehole stratigraphy model To easily simulate Ma_MISS surveys, we first developed a simple model of a borehole. As further described in [2], six different simulant samples were prepared. Reflectance spectra were acquired on each of the samples with DAVIS-MOT, the new Ma_MISS laboratory model[3]. The reflectance spectra of these samples are shown in Figure 1. Six different regions were drawn as polylines on a 2D projection of the cylindrical borehole walls. Out of the six simulants, a different one was assigned to each region. As shown in Figure 2, this model was made to represents a 250 mm deep section of a borehole, exhibiting a varied stratigraphy with 5 different layers and a vertical vein. Figure 1: Reflectance spectra of samples. Figure 2: Borehole stratigraphy model Survey simulation The borehole model can be used to quickly simulate a Ma_MISS survey. Once the acquisition strategy of the survey is defined, the coordinates of the points where spectrometric acquisitions are to be simulated are computed. Small random errors can be added to the coordinates to simulate the accuracy of the drill tool actuators and sensors. For each point of this set, we generate a spectrum that simulates the real acquisition. Each simulated spectrum is generated from the measured spectra of one of the six simulants, based on its region in the stratigraphy model, with the addition of random shifts, slopes, and noise to simulate out-of-focus acquisitions and instrumental noise. Development of acquisition strategies The simulated data can be used to develop acquisition strategies, aimed at maximizing the information gained while limiting the time required to complete a survey of a drilled borehole. The time required to complete the survey depends on both the spectrometer acquisition settings and the drill tool motion. For example, the duration of a drill movement depends on angular and vertical step sizes (hereafter referred to as Δθ and Δz respectively), with vertical translations generally taking longer than rotations. Multiple combination of these parameters can be tried out on the same stratigraphy model to evaluate which strategy can provide the best compromise between spatial resolution and time required. Simulated data examplesFor the 4th RSOWG (Rover Science Operations Working Group) Simulation, held in November 2021, we provided data from a simulated Ma_MISS acquisition survey. The simulated Ma_MISS survey (“survey A”) consisted of: -6 rings of 360 points each, with Δθ=1° and displaced vertically by Δz=50mm; -8 columns made up of 126 points each, taken with Δθ=45° and a vertical step of Δz=2mm.This amounts to a total of 3168 individual spectra. A view of the simulated data is shown in Figure 3 and Figure 5A. This acquisition strategy provides a high angular resolution in the rings with Δθ=1° (which can be useful to identify small vertical features or individual grains) and a good vertical resolution in the column with Δz=2mm (useful to reconstruct the stratigraphy of the subsurface). Another survey (“survey B”) that was simulated with the same model is shown in Figure 4 and Figure 5B-C. In this case the acquisition was made up of 35 rings of 72 points each, with Δθ=5° and Δz=6.25 mm, for a total of 2952 spectra. This strategy offers worse spatial resolution in both the vertical direction and along the circumference but can nonetheless provide a more regular overall view of the borehole stratigraphy. Figure 3: Simulated survey A Figure 4: Simulated survey B Data visualization In Figure 3 and 4, each dot represents a simulated spectrum. In this case the colour of each dot was computed from its spectrum such that it looks somewhat like it would appear to the human eye. The same colours were interpolated across the surface (with a scattered data bicubic interpolation method) to obtain views like those shown in Figure 5A-B. Other useful visualizations of these spectra can be obtained by highlighting other spectral features, e.g., band depths, band ratios or specific IR bands. An example is shown in Figure 5C, where the 1.95 µm band depth is computed on the simulated spectra of survey B and its value is interpolated across the cylindrical surface. Figure 5: Visualization of simulated data on the borehole surface Future work The developed simulation model can be easily extended to other borehole stratigraphy models, with different geometries and spectra. It will also be complemented with tools to estimate the time needed to perform each simulated survey, which will make it a useful tool for the optimization of acquisition strategies. The developed data visualization tools can also be used with real, measured data. We are planning to verify the simulated data on real surveys. In fact, we can perform a complete survey with the Ma_MISS laboratory breadboard on an actual drilled sample. The acquired data will be visualized and used to reconstruct the sample stratigraphy. Acknowledgments This work is supported by the Italian Space Agency (ASI) grant ASI-INAF n. 2017-412-H.0. References[1] De Sanctis M.C. et al. (2017): Astrobiology, 17, 6-7[2] Ferrari M. et al. (2022): LPSC53, Abstract#1339[3] De Angelis S. et al. (2022): LPSC53, Abstract#1796

Introduction: This study is focused on the investigation of the reflected solar light on planetary atmosphere-less bodies, as a function of the viewing geometry (direction of the solar light and direction of the ob-server with respect to the normal to the surface, identifying angles named respectively incidence and emission, and the relative angle between them, named phase). In particular, we focus on the photometric properties of large-scale roughness (hereafter referred to as roughness), which, being not spatially resolved, can be only derived by photometric models. The investigation of the photometric response as a function of roughness is mandatory to disentangle properties of the surface regolith such as albedo, porosity, and thermal inertia (the latter when thermal emission data are avail-able). Moreover, the information on the roughness can be important by itself for interpretation of the geological and physical processes in place, or for engineering use in a case of a landing site selection. Photometric Models: Among the interpretative physically-based models describing the reflection of the light from surfaces, Hapke [1] theory is among the most used in literature, thanks to its completeness in the description of the surface, and the practicality of use, being an analytical model. According to Hapke, a rough surface can be described as a collection of facets, each with a certain slope (θ), in a way that the distribution of slopes is completely identified by a unique parameter (the Mean Slope θ). Random Gaussian and fractal terrains are well-represented by the slope distribution described by Hapke’s theory. This is the case with several minor bodies, targets of recent space missions (e.g., [2]). Hapke developed an analytic formulation to include the effect of the roughness into a general relation describing the reflectance of planetary surfaces, which is a function of several photometric parameters. However, some authors, including Hapke himself, have high-lighted some limitations of this formulation: (i) the parameter that describes roughness is derived in theory only for small angles of the slope of the facets relative to the average surface. This prevents reliable derivation of roughness for more general conditions [1]; (ii) unresolved shadows and self-illumination can affect the overall reflected signal, and if not accurately modeled, can be confused with albedo variation (e.g., [3]). In Hapke’s theory, the dependence of these contributions on observation geometry is treated by means of simpli-fied approximations. An improved approach to the study of rough surfaces has been proposed to overcome the above issues [4]. It consists of a statistical approach in which N unresolved facets, each one having its own viewing geometry, are generated. The integrated resulting signal corresponding to these facets is calculated starting from the response of all facets visible to the observer. This statistical-multi-facets algorithm (SMFA) also takes into account the self-illumination and shadows projected along the observer's line of sight, so that the photometric response is not calculated through analytical ap-proximations, but with the sum of each of the N facets that describe the simulated terrain (see Fig. 1). Roughness retrieval: We investigate the properties of spatially resolved roughness of the dwarf planet Ceres and comet 67P from their shape models, derived by Dawn/NASA and Rosetta/ESA data. From this, we infer the possibility to safely apply the above-mentioned models for retrieval of non-resolved roughness. The latter is performed by the comparison of signals of the surface detected in different viewing geometries. We discuss results coming from both Hapke model and the statistical multi-facets algorithm. Figure 1. An example of the different output between SMFA and Hapke’s models: S = shadowing function, µ0eff = effective incidence angle cosine, µeff = effective emission angle cosine. All these parameters are used by the Hapke formulation, and they are functions of the Mean Slope (θ) parameter. In this example, the incidence, emission, and phase angles are fixed respectively to 30°, 0°, 30° [4]. References: [1] Hapke, Theory of Reflectance and Emittance Spectroscopy, 1993 [2] Davidsson et al., Icarus, 252, 2015 [3] Cuzzi et al., Icarus, 289, 2017 [4] Raponi et al., 14th EPSC 2020, id. EPSC2020-761

Introduction: ExoMars rover Rosalind Franklin will search for traces of past or present life potentially preserved in the designated landing site Oxia Planum [1]. Oxia is located in the western part of Arabia Terra, where geology shows evidence of a past long-lived liquid water body [2]. This clay-bearing plain is overlapped by deltaic system material provided by channels of Coogoon Valles. Spectral detections underlie the possible presence of Fe-rich phyllosilicate (for example vermiculite) and Mg-rich phyllosilicate (for example saponite) mixed with a variable amount of olivine. A mafic coating-resistant unit seems to be present [3,4,5]. Many minerals are expected to be analyzed by the Ma_MISS (Mars Multispectral Imager for Subsurface Studies) instrument at the landing site. The drill is also made up of three extensible 50 cm-long rods. The instrument is a VNIR (0.4–2.3 µm) miniaturized spectrometer in-stalled into the rover drill’s tip. It will acquire borehole spectral images in situ to study the subsurface mineralogy up to 2 m depth with a spatial resolution of 120 µm for looking at organics traces. Ma_MISS is composed of the Optical Head with fibres into the tip and the other fibres in the rods, while the spectrometer and the electronic are outside on the drill box. The sapphire window in the main rod allows the 5W light to illuminate inside the borehole and the reflected signal to be acquired by the spectrometer. The light illuminates a 1 mm diameter spot at ~0.6 mm focal distance. Thanks to drill rotation and vertical movement, Ma_MISS can collect several points to reconstruct a complete borehole image [1]. Laboratory breadboard: Drill for Analogues and Visible-Infrared Spectrometer (DAVIS) is the recent laboratory setup consisting of Laboratory Drill (DAVIS-LD) and Ma_MISS Optical Tool (DAVIS-MOT) (Figure 1). The first one (LD) is the replica of the rover drill except for the spectral acquisition system. The vertical motion is actuated by a hand lever to drill a hole in the rock samples. The motor unit is the same as the flight model but the controller is a commercial EC motor, which control the rotational speed (50 rpm) [6]. The second one (MOT) comprises a 75 cm-long and 25.4 mm-diameter rod, 5W lamp, Sapphire window, Optical Head, and an optical fibre. It is the copy of rover Ma_MISS except for the drilling ability. In this case, rover spectrometer is replaced with two Avantes VIS-NIR spectrometers. The Optical Head fibre is connected with the Avantes fibre through a mini-Avim connector. Being a replica of Ma_MISS, the light spot has 1 mm diameter at ~0.6 mm focal distance and the spatial resolution is 120 µm. It acquire in two different configurations: 1) Slab or powder samples are hosted in a vertical three-axis sample-holder and 2) manual motion of the rod to enter in the sample borehole [7]. Figure 1 – a) Ma_MISS Optical Tool (DAVIS-MOT) and b) Laboratory Drill (DAVIS-LD). Martian Analogue sample: The Martian analogue denominated CAP-1 was collected during a geological survey of the Institute for Space Astrophysics and Planetology (IAPS), in October 2021. It was gathered in 120 cm-depth excavated trench in the area of Capalbio (Tuscany, Italy). It is a Pleistocene metasedimentary rock subjected to hydrothermal alteration/weathering (Figure 2). This brownish siltstone/mudstone is a quite compact rock in dry conditions and brittle in wet conditions. Inside it, there are a few discoidal, sub-angular grains with a diameter higher than 2 mm and different colors (black, reddish, and white), and low sphericity. Grains are not-oriented, except for black Manganese aggregates, which form thin veins with a diameter of about 2-5 mm. Other grains are white rectangular precipitations of Al-bearing clay (kaolinite) and reddish irregular aggregates formed by iron oxide (hematite). The brownish fine-grained (granulometry in the order of silt-clay) matrix has medium porosity, without cement. It lacks stratification and it shows possible alteration due to iron oxidation. CAP-1 is well-sorted, texturally and compositionally mature. The mineral assemblage of the CAP-1 sample is constituted of Mg/Fe smectite, kaolinite, illite, quartz, and minor calcite. It can contain some part of organic material based on analysis of similar soil in the area, but no detectable fossil evidence is found inside. Figure 2 – a) Outcrop where CAP-1 is extracted (sampling depth 30-75 cm); b) Sample Capalbio CAP-1; c) Details of CAP-1 taken under a microscope: Mn aggregates. Discussion and conclusions: Some preliminary acquisitions are taken using the DAVIS-MOT, as we can see in Figure 3. We acquire 3 random points on a planar surface of the sample. After that, raw data of spectra are smoothed and merged between 1075 and 1140 nm (the AVANTES spectrometer has two different detectors and the acquisitions are made for the VIS and IR in two steps). Resampling is done in 364 points between 400 and 2300 nm. Spectra show characteristic absorption bands of water at 1.4 and 1.9 µm, well-shaped absorption bands at 0.95 and 2.2 µm associated with iron transition and Al-OH bond respectively. A deep spectral analysis will be done after the new laboratory acquisition of this sample. Figure 3 – VIS-NIR CAP-1 spectra acquired by DAVIS-MOT. Acknowledgments: This work is supported by the Italian Space Agency (ASI) grant ASI-INAF n. 2017-412-H.0. Ma_MISS is funded by ASI and INAF. References: [1] De Sanctis, M. C. et al. (2017) Astrobiology, 17(6–7), doi: 10.1089/ast.2016.1541; [2] Davis, J. M. et al. (2016) Geology, 44(10), doi: 10.1130/G38247.1; [3] Quantin-Nataf, C. et al. (2021) Astrobiology, 21(3), doi: 10.1089/ast.2019.2191; [4] Mandon, L. et al. (2021) Astrobiology, 21(4), doi: 10.1089/ast.2020.2292; [5] Brossier, J. (2022) Icarus, accepted pending revisions; [6] Rossi, L. et al. (2022) LPSC 53, Abstract #1353, [7] De Angelis, S et al. (2022) LPSC 53, Abstract #1796.

Introduction: Ceres is the largest object of the Solar System main belt with a complex geological and chemical history, which experienced extensive water related processes and geochemical differentiation [1]. Ceres’ surface is characterized by dark materials, phyllosilicates, ammonium-bearing minerals, carbonates, water ice, and salts. In addition to a global presence of carbon-bearing chemistry, local concentration of aliphatic organics has been detected by Dawn mission [2]. The mission, thanks to the data collected by the Italian instrument VIR [3], showed clear evidence of a high amount of aliphatic organic material on the surface of Ceres [4, 5, 6]. This has raised new questions about the origin and preservation of this material, especially when considering its high estimated abundance (Fig 1). We started a series of laboratory studies on physicochemical evolution of organic material interacting with minerals thought to be present on Ceres. The goal is to understand the transformations induced on these samples by processing with ultraviolet radiation. Fig. 1 Ceres spectra of the organic-rich area in Ernutet crater (label “Organics”); of a background organic-poor area from a region southeast of Ernutet (label “Background”); and Occator bright material (label “Carbonate”) [4]. Results: In this study, we mixed organic material with a mixture of minerals considered a spectral analog of the Ceres surface. Specifically, we mixed undecanoic acid and solid material made of serpentine, magnetite, carbonate and ammonium bearing montmorillonite with a ratio of 1:80 (organic:mineral). Diffuse FTIR reflectance spectra were acquired in vacuum. Spectra of simulant are resembling the Ceres surface composition (Fig. 2) organic rich area, even if the proportions between the bands of clays, carbonates and organics are not the same as seen on Ceres. We irradiated the sample in the vacuum chamber at room temperature using an UV lamp to simulate the solar radiation. The photon flux was 2.75x1017 ph. cm-2s-1 in the 200-400 nm spectral range as measured through a single monochromator Spectro 320 spectrometer. The simulant was irradiated at increasing fluence up to irradiation time of about 7 hours and the degradation process was monitored in real time with FTIR spectroscopy by measuring the changes in the spectral features (band areas). In Fig. 4 the reflectance spectra of the simulant as prepared and after UV irradiation at 180, 2280, and 21180 s are showed. The bands area of NH3 at 3 μm and aliphatic CH2/CH3 at 3.4 μm are decreasing as the irradiation fluence increases with time. Fig. 2 Average spectrum of Ceres Ernutet organic-rich ares (black) compared to laboratory simulant (blue). Spectra are normalized at 2.6 μm. Each band area, which is proportional to the number of functional groups, was evaluated at different irradiation time and the degradation rate was obtained by fitting the band areas vs irradiation time using an exponential function. This method permits to determine the degradation cross section of each band, which is the probability that chemical bonds are broken by UV radiation. In particular, for the aliphatic band at 3.4 μm it was possible to obtain the degradation cross section of the whole band, 5.85x10-21 cm2. and of every single band component distinguishing between CH2 and CH3 bonds behavior under irradiation. In presence of mineral simulant, the degradation rate of aliphatic compounds extrapolated to the estimated UV flux at the surface of Ceres gives a half-lifetime of 215 days. This result coupled with resurfacing process time scale of million years could justify the absence of detectable organics on most of the Ceres’ surface. However, this result would not be able to explain the presence of organics in the organic-rich area in Ernutet crater. Furthermore, as can be seen from Fig. 3, UV radiation not only degrades the CH bonds but also affects the NH bonds present in the ammoniated silicates. In this latter case the degradation cross section for the whole band is 2.05x10-21 cm2 which is responsible of a less effective photodegradation process giving a degradation half-lifetime of about 613 days. This result also seems to be in contrast with the ubiquity of the presence of ammoniated silicates on Ceres. We have to recall that the experiments reported in this work have been done at room temperature. It is not excluded that photoprocessing at cryogenic temperature typical of Ceres surface can be less effective further reducing the degradation cross sections of CH and NH bonds. Discussion: As showed by VIR, the ammoniated band is ubiquitous on Ceres, which is in contrast with the fact that we expected the ammoniated band to be completely degraded. However, photodegradation acts on the first molecular layers of the surface exposed to the radiation. Furthermore, the visible and near infrared spectra detected by VIR are diffused by the first millimeters of the surface at a depth that cannot be affected by UV radiation. Therefore, the spectra are a combination of processed superficial material and underlying layers of the Ceres surface, which may retain the primitive characteristics of material rich in organic. However, it should be noted that in addition to UV, the surface is constantly bombarded by solar energetic particles (SEP) and galactic cosmic rays (GCR). This radiation also has the effect of breaking chemical bonds such as UV photons, but penetrating meters into the surface can alter deeper layers. These results suggest that there must be a resurfacing mechanism able to expose organic rich material that acts on a much shorter time scale than the geological one. Fig. 3 Diffuse reflectance spectra of the simulant as prepared (0 s) and after UV irradiation at 180, 2280, and 21180 s. Acknowledgements: This work is supported by INAF Main Stream program, grant “Evolution and alteration of organic material on Ceres”. References: [1] De Sanctis et al., 2016, Nature 536, 54–57 [2] Marchi et al., 2019, Nature Astr. 3, 140-145 [3] De Sanctis et al., 2011, Space Science Reviews 163, 329-369. [4] De Sanctis et al., 2017, Science 355, 719-722 [5] Pieters et al., 2018, Meteoritics and Planetary Science 53 (9), 1983-1998 [6] De Sanctis et al., 2019, MNRAS 482 (2), 2407–2421

In this work, we apply a method previously discussed in [1] to assess the presence of water ice in Mercury’s Polar Shadowed Regions (PSR) mixed to S-rich volatile species like SO2, H2S, and volatile organics, intending to verify their detectability from Bepi Colombo’s orbit and to optimize SIMBIO-SYS/VIHI observations. PSR icy deposits located within the floor of the Kandinsky crater are simulated in terms of I/F spectra corresponding to mixtures of H2O-H2S and H2O-SO2 with grain sizes of 10, 100, and 1000 µm as resulting from indirect illumination by the scattered solar light coming from the crater’s rim. The spectral simulations, performed following the method described in [2], and including the ice-regolith mixing (areal or intimate) as modeled in [3], allow for exploring different volatile species abundances and grain size distribution.The resulting ice detection threshold are evaluated by means of the computation of VIHI’s instrumental signal-to-noise ratio as given by the instrumental radiometric model [4]. In this way, a synergistic use of illumination models, spectral simulations and resulting SNR calculations will help us to optimize the VIHI’s observation strategy across Mercury’s polar regions with the aim to detect, identify and map volatile species. This task is one of the primary scientific goals of the 0.4-2.0 µm Visible and Infrared Hyperspectral Imager (VIHI) [5], one of the three optical channels of the SIMBIO-SYS experiment [6] on ESA’s BepiColombo mission.Due to orbital characteristics and proximity to the Sun, Mercury’s polar regions undergo large variations in illumination conditions during the hermean year [1]. At poles, Permanent Shadowed Regions (PSRs) occur on deep craters and rough morphology terrains that are not directly illuminated by the Sun during the hermean day. Nevertheless, some of these areas could experience partial illumination caused by multiple scattered light coming from nearby illuminated areas. Despite the orbital vicinity to the Sun, Mercury’s PSRs can maintain cryogenic temperatures across geological timescales resulting in the condensation and accumulation of volatile species [7]. While water ice is the more certain species in Mercury’s PSR, it is not precluded the occurrence of other secondary species rich in sulfur or even organic matter.In fact, the total surface area of PSRs between latitudes 80−90° south is not negligible, being estimated at about 25.000 km2 [8], about two times larger than the same geographic area on the North Pole [9]. References: [1] Filacchione G. et al., MNRAS, 498, 1308-1318, 2020. [2] Raponi A. et al., Sci. Adv., 4, eaao3757, 2018. [3] Ciarniello. M. et al., Icarus, 214, 541, 2011. [4] Filacchione G. et al., Rev. Sci. Instrum., 88, 094502, 2017. [5] Capaccioni F. et al., IEEE Trans. Geosci. Remote Sens., 48, 3932, 2010. [6] Cremonese G. et al., Space Sci. Rev., 216, 75, 2020. [7] Paige D. A. et al., Science, 339, 300, 2013. [8] Chabot N. L. et al., J. Geophys. Res., 123, 666, 2018. [9] Deutsch A. N. et al., Icarus, 280, 158, 2016. Acknowledgments: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017- 47-H.0.

Introduction: Various minerals have been detected on Ceres and their abundance and spatial distribution has been mapped in the near infrared spectral domain [i.e. 1, 2]. In this work we study the 1 µm absorption to map Ceres mineralogy at a global scale. It is based on the determination of the whole 1 µm absorption from VIR spectra. VIR is the imaging spectrometer on board the NASA mission Dawn in orbit around Ceres and still operating. VIR is composed of two channels: the VIS channel working in the visible wavelengths between 0.26-1.07 μm and the NIR channel operating in the near infrared between 1.02-5.1 µm. The 1 µm absorption is, indeed, in between the instrument channels. Method: To study the 1 micron spectral range, an automatic method to co-register the VIR and NIR channels, where they overlap, has been implemented, thus allowing the study of this band. After the spatial co-registration, a residual difference in the I/F at 1 µm between the two channels can still remain due to the difference in the PSF’s. To avoid this problem, each VIS spectrum is rescaled to the value of the I/F at ~1 µm of the corresponding NIR spectrum. The exact wavelength at which the two VIR channels are matched, inside the overlapping range between 0.92–1.8 µm, is selected for each spectrum on the basis of the best match. The difference between the VIS and NIR reflectance at ~1 µm (ΔR) is usually 1-2% and only about 1% of data show a ΔR>10%. The spectra with the largest mismatch between the two channels are located along the walls of the craters and valleys where the influence of PSF differences is expected to be larger. In this study the data with ΔR>10% are discarded. The maps have global longitudinal coverage, latitudinal coverage from 66°S to 66°N, and a spatial resolution of ~1.86 km/pixel at the equator. Each spectrum of the surface is the result of areal or intimate mixing of different minerals, and the resulting spectral reflectance properties are a complex combination of the spectra of each mineral end-member. Several studies have shown that it is possible to explore Ceres mineralogical diversity utilizing specific spectral parameters [1,2]. In order to extract compositional information from the spectra, we have introduced some spectral indices and studied the correlations between them all over the VIR data set. Global maps of the 1 µm signature on Ceres have been derived from various spectral indices, such as band centers, depths, integrated areas, etc. Results: A better understanding of the spatial distribution and the content of the different mineral phases can thus be obtained by investigating the spectral characteristics of the 1 µm band. In general, the VIR spectrum of Ceres is dominated by a broad absorption at about 1.2 µm. It is mostly uniform across the surface, but some differences can be seen in the map of the band parametres, like the band depth. Variation in the band depth could be due to various factors, such as relative abundance and grain size of the present minerals. However, the spectral properties of the 1 µm band have been related to other spectral parameters in the NIR domain where mineralogy is known. For example, the attribution of the 3.1 µm band to ammonia-bearing species [1] show that this mineral phase dominant where we see for low values of 1 micron band. Infact, the spatial variability in the 1.0 µm band intensity is anticorrelated respect to the 3.1 µm band. Some terrains show a different behavior of the 1 micron band respect to 3.1 band. This suggests the presence of a distinctive mineralogy. This work, together with the results of other authors [1,2], completes the global mapping of the Ceres mineralogy. Acknowledgments: We thank the Italian Space Agency (ASI). The Visible and Infrared Mapping Spectrometer (VIR) was funded and coordinated by the Italian Space Agency, with the scientific leadership of the Institute for Space Astrophysics and Planetology, Italian National Institute for Astrophysics, Italy. References: [1] E. Ammannito et al. (2016) Science, 353, issue 6303. [2] Carrozzo et al. (2018), Science Advances, vol. 4, 3, e1701645.

Introduction: The comprehension and interpretation of VIS-IR spectra from space missions to Solar System rocky bodies is generally based on the qualitative/quantitative comparison with standard laboratory datasets [1,2,3,4], i.e. spectra often acquired in laboratory at room pressure/temperature, so dominated by water bands [5]. We developed the new laboratory setup CAPSULA (Chamber for Analogues of Planetary Surfaces Laboratory), consisting of an environmental chamber equipped with a FTIR spectrometer to acquire spectra of planetary analogues in various conditions. The chamber allows to obtain (i) high vacuum (-6 mb); (ii) high (>1000K) and cryogenic T (Setup description: The CAPSULA setup is hosted at INAF-IAPS C-Lab laboratory (fig.1). It is constituted by (i) a Bruker Fourier Transform Infrared (FTIR) spectrometer, equipped with an MCT and DLaTGS detectors and (ii) a large high vacuum chamber 50x60 cm, in which the samples to be analyzed are placed. The chamber and the spectrometer are coupled by means of optical fiber bundles, each composed by seven 200/260-mm core/cladding fibers. Although the FTIR detectors are sensitive up to 20 µm, currently the fibers, in Indium Fluoride Glass, allow the signal to be transmitted in the 0.35-5.5 µm range. The illumination spot on the sample (at angle of 30°) and the collection spot (at 0°) are 3N4 heaters, placed just below copper sampleholders cups, allows to heat samples up to 1073K in high vacuum. A liquid He compressor connected to a cold head within the chamber permits to cool down the samples at cryogenic temperatures below 80K.Preliminary tests and measurements: As preliminary activity the optical fibers have been extensively characterized in the laboratory in terms of spectral transmission, in the 0.35-5.5-µm range, resulting in an average transmission of at least 80% for each fiber.With the aim of starting to test the setup, preliminary spectral measurements have been performed on a powder sample of ammoniated montmorillonite (NH4-SCa3) [6,7] (fig.2). The sample, in the form of 1 µm) and NIR source spectrum cut-off (3 mbar), then at 5, 4, 3 mbar and down to 10-6 mbar. Each spectrum (both reference and sample) is acquired by doing 512 scans with the FTIR interferometer, which takes about 2’. During this time the pressure changed very slowly, i.e. by less than 5%. It can be seen how dehydration proceeds during the pumping, as seen by the decrease of H2O bands at 1.5, 2 and 3 µm. Correspondingly absorption features due to NH4+ become clearly visible (1.55, 2.1-2.2, 3.1 and 3.25 µm) (fig.3). Future work:We are currently testing the different subsystems of the setup (cooling/heating system) and working on several upgrades of the experimental system, including the extension of the spectral range in the mid-IR (above 5 µm) through the use of mirrors. We are in parallel starting to carry out scientific measurements on analogues of different planetary rocky objects (Mars, Ceres) with the current setup.References: [1] De Sanctis M.C. et al. (2015), Nature Letter 528, 241-244. [2] Elkins-Tanton L.T., et al.: (2016) XLVII LPSC, abstract #1631. [3] Hamilton V.E., et al. (2019) Nature Astronomy. [4] Kitazato K., et al. (2019), Science, 364, 272-275. [5] Beck P., et al. (2018) Icarus 313, 124–138. [6] Ferrari M., et al. (2019) Icarus. [7] De Angelis S., et al. (2021), JGR:Planets, V.126, Is.5, e2020JE006696.Acknowledgements: The CAPSULA project has been funded in the framework of ASI-INAF Announcement of Opportunity in 2018 for Solar System studies, with a two years grant. We acknowledge financial contribution from the Agreement ASI-INAF n.2018-16-HH.0.

The ExoMars rover mission will be looking for biosignatures (i.e. signs of past and present life) in Oxia Planum, Mars [1]. The landing site is located between 16° and 19° N and 334° to 337° E where the ancient cratered terrains transition into the low-lying plains of Chryse Planitia. The area of interest is situated between Ares Vallis and Marwth Vallis in a wide basin at the outlet of Cogoon Vallis. The fractures, extensively spread over the terrains of the landing site, range from meters to decameters in spacing and length and have been preliminary interpreted as desiccation cracks or the result of burial and unloading of sediments [2,3]. We mapped these fractured terrains and we tested an automatic method for alignment tracing which contributes to our study in an effort to evaluate the directional aspects of fracturing and their spatial distribution within the study area. The data we used come from VNIR pushbroom imager camera HiRISE, which produces the highest resolution images of the martian surface (25 to 60 cm/pixel) [4]. 31 greyscale HiRISE RED products (25 cm/pixels) and three HiRISE colour product (60 cm/pixel) covering the landing ellipse were selected and downloaded from the Planetary Data System (PDS) [5], and imported into QGIS (version 3.24.1 Tisler) [6]. To map these fractures over a submeter resolution basemap within the ≥1000 km2 landing ellipse area, we opted to use a 1:5000 scale. We mapped the boundaries of the fractured area as lines, generating category areas from the boundaries of the mapped area through the Mappy QGIS plugin [7]. We classified the fractures by their association with sand, dunes, TARs and ridges. Using the resulting map of the fractured terrains, we placed a 200 m2 Scan Area on a place where fracturing was more evident: we extracted HiRISE data that was input into the Slope Intersect Discrete Analysis (SID) software version 3.04-10 for automatic tracing of the fractures. The results of automatic tracing, whose algorithm is based on a modified Hugh transform [8], was further processed in to GRASS GIS [9]: the GRASS Toolset v.clean was used to snap vertices of SID output. To compare the manual and automatic methods, the Scan Area input by SID has been used to manually trace fractures at 1:1000 scale, whose orientation in the space was obtained using Daisy software version 3-5.51-3. The map of the fractured terrains was then used to place multiple Scan Areas where fracturing is more evident (Fig.2). The automatic fracture tracing method will be applied on other areas of interest in future studies. We classified fractured terrains into three categories where we placed 28 Scan Areas (Fig.1) : we placed nine of them in terrains characterized mainly by fractures (MF, lower portion of the map), 10 in terrains associated with the presence of linear topographic rises (ridges) (RF, central portion of the map) and nine in fractured terrains with an abundance of sand and dunes (SF, upper portion of the map). 507 fractures were traced manually ranging 1.14-68.4 m in length (Fig.2, b). In the automatic method, SID mapped 1712 elements between 2 and 21 m in length (Fig.2, a). Regarding the directional Azimuth-Frequency analysis carried out by Daisy, the average orientation is very similar: fractures traced manually indicate a value of 92.26° (sd: 12.5°) and fractures traced via SID correspond to a value of 93.06° (sd: 15.97°) (Fig.2, a, b below). The spatial distribution of fractures traced manually is homogeneous, including both the longest and the shortest fractures. The few areas where the absence of fractures is observed are those where there is a strong cover of sand. The longer fractures do not create intersections, if not with the shorter ones, which cross each other, forming small networks. The homogeneous distribution of manually traced fractures is the same as those traced unsupervised via SID. The differences instead occur mainly in the number and in the length of lines traced in the two methods: SID’s sensitivity to low variations of DN result in a greater number of identified fractures through segments with a defined minimum and maximum length. However, not all manually traced fractures have been identified by SID. No matter how efficient the GRASS GIS toolset is, fractures traced by SID too far apart from eachother were not considered a single element, which the human interpretation would have done. As far as orientation is concerned, the two methods show very similar values. This study shows how, although the clear differences between manually and automatic method, the latter may prove to be efficient, even considering their limitations. SID’s fracture tracing in fact guarantees a strong effectiveness for the calculation of their orientations. Further analysis in the Scan Areas placed on the fractured terrains of the landing ellipse will verify whether or not there are anisotropies in the orientation of the fractures, which will help improve our knowledge about the formation and evolution of Oxia Planum. References [1] Vago et al.(2017), Astrobiology, Vol. 17, No. 6-7. [2] Quantin-Nataf et al. (2021) Astrobiology 21, 345. [3] Bowen et al. (2022) Planetary and Space Science Volume 2014. [4] McEwen et al. (2007) Journal of Geophysical Research: Planets Volume 112, [5] McMahon (1995) Planetary and Space Science Volume 44 [6] Casagrande et al., (2014) Dario Flaccovio Editore p. 220 [7] Penasa et al. (2020) European Planetary Science Congress, Volume 14 [8] Hough (1959) HEACC, Proceedings of the 2nd International Conference on High-Energy Accelerators and Instrumentation [9] Neteler and Mitasova (2013) The Springer International Series in Engineering and Computer Science Figure 1 – Fractured terrains mapping and Scan Area locations within the ExoMars landing ellipse. Geospatial data is in simple cylindrical projection, considering Mars Sphere (IAU2018:49910). Figure 2 - Comparison between automatic (a) and manual tracing (b). The tables show results of the directional analysis effectuated by Daisy.

Linear features are very common on asteroid surfaces. They are generally formed after impact and provide information about asteroid evolution. This work focuses on a mineralogical and spectral analysis of the main linear features on the 1/Ceres surface, having both tectonic (Samhain Catena’s pit chains) and geomorphic origins, i.e., generated by ejecta material (Occator ejecta, Dantu’s secondary radial chains, secondary radial chains generated from the Urvara impact). The analysis is based on spectral parameters defined by the Dawn’s VIR imaging spectrometer data, as albedo and depths of the bands centered at approximately 2.7, 3.1, 3.4 and 3.9 mm. The geomorphic linear features show spectral variations with respect to the surroundings, i.e., ammoniated phyllosilicates band depth shallowing is caused by the presence of material originating in a different region or dehydration caused by impact. The Samhain Catena does not show any mineralogical variation, due to its tectonic origin. The spectral behavior of Ceres’ linear features is similar to that observed on other asteroids (Vesta, Eros) and can be diagnostic in discerning the origin of linear features. Then, we searched spectral signatures of organics in the Samhain Catena region, since they are expected to form at depth due to internal processes: the absence of such signatures indicates that either they form at a larger depth or that their subsurface distribution is uneven.

Introduction. ExoMars rover mission is planned to deliver the ‘Rosalind Franklin’ rover to explore Oxia Planum, a region that straddles between Arabia Terra and Chryse Planitia (335.5E, 18.2N). Oxia Planum bears several evidences of aqueous activity [1-4], where infrared data reveal extensive outcrops of recently exhumed clay-rich rocks. These outcrops are perfect “windows” to search for signs of past or present life on Mars, as biosignatures might be preserved therein [5]. Clays detected at Oxia Planum are among those found all over circum-Chryse Planitia [6], a flat lowland region and bottom end of many outflow channels. Here, we focus on possible clay-bearing outcrops detected in northern Xanthe Terra (313E, 13N) (Figure 1), a region that has already been suggested for several rover missions. Like in Oxia Planum, several morphological features advocate for a fluvio-deltaic and lacustrine history in the region [7-9], with fluvial channels and fan deltas (e.g., Sabrina and Hypanis valley systems). Despite a possible detection of Fe,Mg-rich clays at the Sabrina delta [10,11], no detailed spectral survey have been done in the entire area. A detailed analysis of these outcrops is crucial to better determine possible mineral phase(s) and search for changes in clay mineralogies associated with differences in formation and weathering conditions. We examine infrared data, particularly the absorptions centered in the 1.0–2.6 μm spectral range, in order to better constrain the nature and composition of the clays. Figure 1 – Locations of Oxia Planum (OP) and northern Xanthe Terra (XT) at the margins of circum-Chryse Planitia. Data & Methods. Spectral signatures of the clay outcrops are obtained from data gathered by the CRISM instrument, with spatial resolutions of 20–40 m.px-1 and a spectral resolution of 6.6 nm [12]. For this study we use several CRISM cubes acquired in the near-infrared spectral range (1–4 µm), targeting the northern Xanthe Terra. They are first pre-processed through CAT ENVI for atmospheric and photometric corrections. Corrected cubes are then denoised (column-by-column ratio) to reduce noise and residual atmospheric contributions, and to finally emphasize mineralogical absorptions in the ratioed spectrum. Once the cubes are corrected and denoised, we define our regions of interest (ROIs) to outline clays. We calculate band depths at 1.9 and 2.3 µm [13] to select pixels with strong absorptions and map the ROIs for each cube (Figure 2). Figure 2 – Two sites of interest exposing clay-bearing outcrops: near the Sabrina fan delta at the Magong crater (313.4E, 12.1N) and an isolated outcrop in eastern Xanthe Terra (317.5E, 10N). We also include the possible clay outcrops identified at the delta [10,11]. Results. For each cube, we retrieve the band centers for all pixel of the ROIs within the three spectral ranges of interest: 1.4 µm (1.37–1.45), 1.9 µm (1.88–1.96), and 2.3 µm (2.26–2.34) (after continuum removal to emphasize the absorptions). The band centers do not strongly vary for the three narrow absorptions, with average values being 1.408 ± 0.009 µm, 1.923 ± 0.008 µm, and 2.305 ± 0.009 µm. FRT0A605 is the only cube displaying a clear overtone near 2.4 µm and a shallow absorption near 2.5 µm. We therefore retrieve the band centers near 2.4 µm (2.36–2.44) and 2.5 µm (2.49–2.57), where the cube shows average values of 2.397 ± 0.009 µm, and 2.530 ± 0.010 µm. Overall, these values are identical to those recently obtained at Oxia Planum [4] (Figure 3). Figure 3 – (left) Spectra of CRISM denoised reflectance (normalized and offset for clarity) obtained in northern Xanthe Terra. (top right) We also include three spectra from Oxia Planum [4]. (bottom right) Lab spectra of main candidate Fe,Mg-rich clays (RELAB). Discussion. CRISM cubes reveal several absorptions in the 1.1–2.6 µm range. Absorptions near 1.4 and 1.9 µm are common to hydrated minerals (OH/H2O stretching), while an absorption near 2.3 µm indicates a (Fe,Mg)-OH vibration. Xanthe’s clays are consistent with Fe,Mg-rich clays, combining absorptions at 1.41, 1.92, 2.30–2.31 µm and weaker overtones near 2.39–2.40 µm. Martian Fe,Mg-rich clays generally show spectral variability in the three windows. Xanthe’s clays intermediate band centers are consistent with either vermiculites and Fe-rich saponite (Figure 3), like in Oxia [4]. Band centers within these windows vary very little throughout the region. Exact positions therein depend on the relative abundance of iron and magnesium in the clay structure, and also oxidation state of iron. Conclusions. We provide in-depth information on the clay-bearing outcrops found in northern Xanthe Terra, to compare with recent results obtained in Oxia Planum [2,4]: (1) report exact positions of the 1.4, 1.9, 2.3, 2.4 and 2.5 µm absorption bands, and (2) map the “purest” clays in the targeted areas, in context with the morphology and topography. This allows for further investigations in context with the ExoMars rover mission or other future rover missions. Acknowledgments. This work is fully funded and supported by the Italian Space Agency (ASI) [Grant ASI-INAF n. 2017-48-H.0]. We are greatly thankful to the CRISM team for the CAT tool, and European Space Agency (ESA) and Russian Space Agency ROSCOSMOS for the ExoMars project. References. [1] Carter et al. (2016) 47th LPSC Abstracts, 2064. [2] Mandon et al. (2021) Astrobiology 21, 464–480. [3] Quantin-Nataf et al. (2021) Astrobiology 21, 345–366. [4] Brossier et al. (under review) Icarus. [5] Vago et al. (2017) Astrobiology 17, 471–510. [6] Carter et al. (2013) JGR 118, 831–858. [7] Fawdon et al. (2018) EPSL 500, 225–241. [8] Adler et al. (2019) Icarus 319, 885–908. [9] Adler et al. (2022) JGR 127, e2021JE006994. [10] Platz et al. (2014) 9th EPSC Abstracts, 811. [11] Knade et al. (2017) 11th EPSC Abstracts, 692-1. [12] Murchie et al. (2007) JGR 112, E05S03; Murchie et al. (2009) JGR 114, E00D07. [13] Viviano-Beck et al. (2014) JGR 119, 1403–1431. [14] Ehlmann et al. (2008) Science 322, 1828–1832.

The Dawn mission found that the dominant colour variation on the surface of dwarf planet Ceres is a change of the visible spectral slope, where fresh impact craters are surrounded by blue (negative spectral-sloped) ejecta. The origin of this colour variation is still a mystery. Here we investigate a scenario in which an impact mixes the phyllosilicates present on the surface of Ceres with the water ice just below. In our experiment, Ceres analogue material is suspended in liquid water to create intimately mixed ice particles, which are sublimated under conditions approximating those on Ceres. The sublimation residue has a highly porous, foam-like structure made of phyllosilicates that scattered light in similar blue fashion as the Ceres surface. Our experiment provides a mechanism for the blue colour of fresh craters that can naturally emerge from the Ceres environment., The origin of blue ejecta around the fresh craters of dwarf planet Ceres is unknown. Here, the authors show that the blue color results from high porosity of the surface, induced by sublimation of ice-phyllosilicate mixture produced by impacts.

International audience; Ceres, the most water-rich body in the inner solar system after Earth, has recently been recognized to have astrobiological importance. Chemical and physical measurements obtained by the Dawn mission enabled the quantification of key parameters, which helped to constrain the habitability of the inner solar system's only dwarf planet. The surface chemistry and internal structure of Ceres testify to a protracted history of reactions between liquid water, rock, and likely organic compounds. We review the clues on chemical composition, temperature, and prospects for long-term occurrence of liquid and chemical gradients. Comparisons with giant planet satellites indicate similarities both from a chemical evolution standpoint and in the physical mechanisms driving Ceres' internal evolution.

Comets evolve due to sublimation of ices embedded inside porous dust, triggering dust emission (that is, erosion) followed by mass loss, mass redistribution and surface modifications. Surface changes were revealed by the Deep Impact and Stardust NExT missions for comet 9P/Tempel 1 (ref. 1), and a full inventory of the processes modifying cometary nuclei was provided by Rosetta while it escorted comet 67P/Churyumov–Gerasimenko for approximately two years2–4. Such observations also showed puzzling water-ice-rich spots that stood out as patches optically brighter and spectrally bluer than the average cometary surface5–9. These are up to tens of metres large and indicate macroscopic compositional dishomogeneities apparently in contrast with the structural homogeneity above centimetre scales of pebble-made nuclei10. Here we show that the occurrence of blue patches determines the seasonal variability of the nucleus colour4,11,12 and gives insight into the internal structure of comets. We define a new model that links the centimetre-sized pebbles composing the nucleus10 and driving cometary activity13,14 to metre-sized water-ice-enriched blocks embedded in a drier matrix. The emergence of blue patches is due to the matrix erosion driven by CO2-ice sublimation that exposes the water-ice-enriched blocks, which in turn are eroded by water-ice sublimation when exposed to sunlight. Our model explains the observed seasonal evolution of the nucleus and reconciles the available data at micro (sub-centimetre) and macro (metre) scales.

Up to now, only (4) Vesta has been identified as the source of differentiated material, which has been discovered all around the Main Belt region. Most of the basaltic asteroids, identified through spectroscopic measurements, are located in the inner main belt region (2.15-2.5AU) and constitute the Vesta family. These asteroids are indeed dynamically linked to Vesta and share similar spectroscopic properties, showing the absorption bands at 0.92-0.94 micron and 2.0 micron, which are indicative of a basaltic composition. From a dynamical point of view, these objects have proper semimajor axis ap, eccentricity ep and inclination ip in the ranges 2.26 < ap < 2.48, 0.075 < ep p < 7.9°, respectively (Nesvorny et al. 2015). In addition, a faint absorption band at 0.506 micron, due to a spin forbidden transition of Fe2+, was recently detected also in some V-type asteroids, both members and non-members of the Vesta family (Migliorini et al. 2021). Ground-based observations have shown that few asteroids distributed beyond the 3:1 MMR (Mean Motion Resonance) at 2.5 AU have a basaltic composition (Lazzaro et al. 2000; Hardersen et al. 2004, 2018; Roig et al. 2008; De Sanctis et al. 2011; Solontoi et al. 2012; Ieva et al. 2018; Leith et al. 2017; Migliorini et al. 2018, 2021; Medeiros et al. 2019), although with some differences with respect to Vesta and its family members (Jasmim et al. 2013). Thus, their origin seems to be likely linked to the break-up of large, differentiated objects other than Vesta. Dynamical studies allowed the identification of possible asteroid families, like (221) Eos, (1272) Gefion and (1040) Klumpkea families, which could be the result of the disruption of a differentiated or partly-differentiated parent body. These asteroid families include members with very different spectral types, including basaltic asteroids. Among the asteroids we observed in a previous ground-based campaign, some confirmed V-type asteroids were found to be members of these identified asteroid families, while others lay close to these asteroid families (Migliorini et al. 2021). In the figure below, confirmed basaltic asteroids located beyond 2.5 AU are shown in the proper a- proper I plane and indicated with a circle. Asteroid families are also marked with different colors. Some objects classified as M- (crosses) and A- type (triangles) are also included. We started a new observing campaign to spectrally characterize asteroids selected among the above listed asteroid families, aiming to identify other members with a basaltic composition. In this work we revise the spectral and dynamical properties of basaltic asteroids in the middle and outer main belt, not related to Vesta, and recent observations of asteroids members of the (221) Eos, (1272) Gefion and (1040) Klumpkea families. Figure 1. a-i plane of proper semimajor axis and inclination of the middle (left) and outer (right) main belt. Basaltic asteroids from Migliorini et al. (2021) are shown with circles. Some are identified as members of the asteroids families shaped with different colors, while some are locate close to these families. Some M- type and A- type asteroids, located in the same region, are also reported with crosses and triangles, respectively, for comparison. References De Sanctis M.C. et al. 2011, A&A, 533, A77. Hardersen P.S. et al. 2004, Icarus, 159, 178. Hardersen P.S. et al. 2018, AJ, 156, 11. Ieva S. et al. 2018, MNRAS, 479, 2607. Jasmim F.L. et al. 2013, A&A, 552, A85. Lazzaro D. et al. 2000, Science, 288, 2033. Leith T.B. et al. 2017, Icarus, 205, 61. Medeiros H. et al. 2019, MNRAS, 488, 3866. Migliorini A. et al. 2018, MNRAS, 475, 353. Migliorini A. et al. 2021, MNRAS, 504, 2019. Nesvorny D. et al. 2015, Asteroids IV, p. 895. Roig F. et al. 2008, Icarus, 194, 125. Solontoi M. et al. 2012, Icarus, 218, 571.

Introduction: The 4 Vesta asteroid is a differentiated asteroid, i.e. it has experienced melting and its structure is distinct layered: crust, mantle, nucleus. Hence, study of materials from different depths of Vesta would be helpful to understand its evolutionary history. Moreover, Vesta preserves information on the composition of primordial smaller asteroids that impacted on its surface. Vesta bright surface shows indeed dark units [1], that are supposed to be linked to exogenous material, and are therefore useful to understand the initial stages of the Solar System. The VIR spectrometer on board the NASA’s Dawn spacecraft [2], that orbited Vesta for approximately one year, collected thousands of hyperspectral images of its surface. Vesta spectra show the 2.7-2.8 μm absorption band, due to the presence of the OH molecule, whose distribution is inversely correlated with the reflectance of its surface [3]. In fact, it is included in carbonaceous chondrites, that are the darkening agents of the Vesta’s dark units [4]. Scientific Objectives: In this work we took advantage of the newly calibrated data of the VIR spectrometer, which are characterized by a better signal to noise (S/N) ratio, giving us the opportunity to search for spectral features that were never seen before, due to noise. Basing on this, the goals of this work were to: 1) confirm, reinforce and characterize the OH distribution on Vesta by studying the 2.7-2.8 µm band and by looking for OH combination bands that occur around 2.2-2.4 µm; 2) search for and characterize possible carbonates, that are supposed to be included in carbonaceous chondrites, i.e., the darkening agents of Vesta; 3) characterize the Vesta surface in the visible range. OH absorption band: The analysis on absorption bands related to the hydroxyl evidenced an anticorrelation between the abundance of hydroxyl and the reflectance of the surface (Figure 1). This confirms that the OH molecule is linked to the presence of the dark units on Vesta [3]. This is also a definitive proof that dark hydrated impactors (likely carbonaceous chondrites) are the darkening agents on Vesta, ruling out other interpretations suggested in literature (regolith grain size, impact shock and presence of opaque-rich eucrites and metals) [1]. Figure 1: Anti-correlation between the 2.8 µm band depth and the reflectance of the surface. We searched for the presence of possible combination bands centered around 2.2-2.4 µm. Weak features at 2.4 µm were found but no correlation with the 2.8 µm absorption band has been proved, so we can say that this feature is not related to the OH molecule and is likely a spectral artifact (Figure 2). Figure 2: This scatterplot shows that the 2.4 µm feature is not correlated to the 2.8 µm absorption band. Search for carbonates: We were not able to identify the 3.9 µm and the 3.4 µm absorption bands related to the presence of carbonates. This does not necessarily mean that carbonates are absent, but their abundance is not sufficient to observe an absorption band emerging from spectral noise. We compared VIR spectra with synthetic spectra of Vesta analogous mixtures (developed by applying a radiative transfer model) to calculate the upper limit of the abundance of carbonates on Vesta. The results show that carbonaceous chondrites that impacted on Vesta, contain no more than 0.5-2% of carbonates, in agreement with petrochemical analyses of typical Carbonaceous chondrites [5]. Caracterization in the visible range: The visible spectra showed an absorption band around 0.5 µm in addition to the strongest well known pyroxenes absorption band centered at 0.9 µm. We made a scatterplot between the 0.5 µm band depth and the 1.9 µm band depth related to the pyroxenes (Figure 3). In the scatterplot a linear dependance between the two features is evident. This proves that the 0.5 µm absorption band is due to the presence of the pyroxenes. Other features found in the visible range were instead associated to spectral artifacts. This emphasizes the results found by [6]. Figure 3: Correlation between the absorption band at 0.5 µm and the absorption band of the pyroxenes at 1.9 µm. References: [1] Palomba E. et al. (2014) Icarus, 240, 58–72. [2] De Sanctis M. C. et al. (2011) SSR, 163, 329. [3] De Sanctis M. C. et al. (2012) The astrophysical Journal Letters., 758.2, p. L36. [4] McCord T. B. et al. (2012) Nature, 491.7422 , 83-86. [5] de Leuw S., Rubin A. E., Wasson, J. T. (2010) Meteoritics & Planetary Science, 45.4, 513-530. [6] Rousseau B. e al. (2021) Astronomy and Astrophysics, 653.

Introduction The selected landing site of the ExoMars mission (Oxia Planum) [1] shows mineralogical and morphological evidence that it was characterized by a hydrothermal history and by a long duration of aqueous superficial activity [2; 3]. These factors are consistent with conditions favourable to life development. In this framework, we planned a field campaign in the Rio Tinto [4] area (Europlanet TA1 facility 2) where to perform a set of VIS-NIR measurements using our portable spectrometer. In addition, for each analyzed mineral/rock on-field, we collect a representative sample to be measured with the Ma_MISS instrument laboratory model. Fig.1: TA1.2 Rio Tinto, south-west Spain a very acidic 100 km river with intense red dark colour (credits F. Gomez). The Ma_MISS instrument Ma_MISS is the Visible and Near-Infrared miniaturized spectrometer hosted in the drill system of the ExoMars rover that will characterize the mineralogy and stratigraphy of the excavated borehole wall at different depths (2O and hydrated phases; (3) characterize important optical and physical properties of the materials (e.g., grain size); (4) produce a stratigraphic column that will provide information on the subsurface geology. Ma_MISS will operate periodically during pauses in drilling activity and will produce hyperspectral images of the drill’s borehole. Field activity During the field campaign, we perform a set of VIS-NIR (0.35 – 2.5 μm) measurements using our ASD FieldSpec4 portable spectrometer on biosignatures-bearing rocks and acidic alteration products. For each selected lithotype we collect several reflectance spectra using solar light as the light source and a 99% Spectralon target as a reference in the VIS-NIR range, with particular attention to those that hypothetically host organic matter in the form of bacterial communities. In addition, for each measured mineral/rock we collect a representative sample to be used for the laboratory measurements with the Ma_MISS laboratory model. With this setup, it is possible to perform measurements with samples in different configurations (powders, slabs, or holed rock blocks); hence, we collect samples with different specific dimensions. In the case of incoherent sediments/salts, we sample a minimum amount of 20-30 g. On the contrary, in the case of coherent samples, we collect blocks with a maximum size of 10x10x10 cm, which are the optimal dimensions useful for performing the drilling operations and in-hole measurements with the DAVIS setup [6,7]. For each collected sample, we record the following data at the time of collection: imagery of the context and the sampling site with a reference scale, the three-dimensional orientation of the sample, and the geographic coordinates at the collection point using a GNSS dual-frequency GPS. Every sample is sealed in a specific container to avoid any contamination [8]. The samples’ metadata are registered in the System for Earth Samples Registration (SESAR) for long-term archival of the physical samples which can be retrieved from a unique ISGN code (isgn.org) for referencing in this and future projects. Laboratory activity The collected samples were measured with the DAVIS (Drill for Analogues and Visible-Infrared Spectrometer) setup at the INAF-IAPS laboratories. This laboratory facility is constituted by a drilling tool that reproduces the ExoMars Drill functionality (Laboratory Drill, LD [6]) and by a measurement tool, reproducing Ma_MISS optical characteristics (Ma_MISS Optical Tool, MOT [7]). Consisting of spare elements of the flight instrument, the DAVIS setup can be considered an instrument completely comparable to the one that will investigate the Martian subsurface. For this reason, the measurements on the collected samples become very important for instrument characterization and future data interpretation. The collected sample blocks are drilled to obtain a hole with the same characteristics as those that the ExoMars drill will do on Mars. Finally, we perform a series of in-hole spectral scans to characterize the chemical-physical properties of the collected samples. The data collected on-field and in the laboratory are analyzed and compared to reconstruct the composition of the analyzed samples. We will focus our efforts on any spectral signature related to the presence of biomarkers in the collected data since we know that the Ma_MISS tool can aid in detecting organics [9] in the Martian subsoil, which is one of the main scientific objectives of the ExoMars mission. Conclusions In this work, we describe the procedures followed during our geological field analysis campaign in the Rio Tinto area. This geologically/biologically well-documented site with its rock/water/biology interaction represents an ideal open-air laboratory where to collect spectral data and samples useful for testing the ExoMars/Ma_MISS spectrometer. The scientific results obtained by this and previous works made with other drilling equipment [10] and with other scientific instruments [11] confirm that this type of activity in the Rio Tinto area site is important for enriching the scientific community's grasp on the Martian environment and for obtaining key information on the mineralogical and geochemical evolution of the Martian surface/subsurface. In addition, this work provides crucial preparation for the exploitation and interpretation of the scientific data that the Ma_MISS instrument will supply during the active phase of the mission. This activity is also useful for defining the priorities of the astrobiological objectives on the ground. Acknowledgements This work is supported by the Italian Space Agency grant ASI-INAF n. 2017-412-H.0. Ma_MISS is funded by ASI and INAF. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 871149. References [1]Vago, J.L. et al. (2017) Astrobiology; [2]Mandon, L. et al. (2021) Astrobiology; [3]Quantin-Nataf, C. et al. (2021) Astrobiology; [4]Amils, R. et al. (2014) Life; [5]De Sanctis, M.C. et al. (2017) Astrobiology; [6]Rossi, L. et al. (2022) 53rd LPSC #1353; [7]De Angelis, S. et al. 53rd LPSC (2022) #1796; [8]Cockell, C.S., et al. (2019) Space Sci Rev. [9]Ferrari, M. et al. (2020), EPSC2020-348; [10]Bonaccorsi, R. et al (2008) Astrobiology; [11]Gomez, F. et al., (2011) Int. J. Astrobiology.

Remote sensing data of comets 9P/Tempel 1 and 67P/Churyumov-Gerasimenko (67P hereafter) indicate the occurrence of water-ice-rich spots on the surface of cometary nuclei [1-5]. These spots are up to tens of metres in size and appear brighter and bluer than the average surface at visible wavelengths. In addition, the extensive observation campaign performed by the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS, [6]) and the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, [7]) during the Rosetta escort phase at 67P revealed a seasonal cycle of the nucleus colour. This is characterised by blueing of the surface while approaching perihelion followed by progressive reddening and restoral of the original colour along the outbound orbit. The temporal evolution of the colour has been interpreted in previous studies as the result of increasing exposure of water ice at smaller heliocentric distances [8, 9], however, an explanation of such seasonal cycle in the context of a quantitative cometary activity model was not yet been provided. Recently, in [10] we showed that the seasonal colour cycle observed on comet 67P is determined by the occurrence of the above-mentioned water-ice-rich spots (referred to as Blue Patches – BPs –, given their colour). This can be explained in the context of activity models [11, 12] of pebble-made cometary nuclei [13], i.e. in terms of nucleus surface erosion induced by H2O and CO2 ices sublimation, driving the cometary activity. According to the scenario proposed in [10] (Fig. 1), the presence of the BPs is due to the exposure of subsurface sub-metre-sized Water-ice-Enriched Blocks (WEBs) thanks to surface erosion triggered by CO2 sublimation ejecting decimetre-sized chunks [12]. The WEBs are composed of ice-rich pebbles (dust-to-ice mass ratio δ=2, [14]), embedded in a matrix of drier pebbles (δ>>5) forming most of the nucleus. Once exposed to illumination as BPs, the WEBs are eroded by water-ice sublimation ejecting sub-cm dust [11]. By means of dedicated spectral and thermophysical modelling, we match the nucleus colour temporal evolution measured by the VIRTIS Mapping channel in the 0.55-0.8 µm spectral range. In doing this, we take into account the competing effects of CO2- and H2O-driven erosion that expose and remove the BPs, respectively, and are seasonally modulated by the insolation conditions, primarily depending on the heliocentric distance. The new nucleus model proposed in [10], implying an uneven distribution of water ice in cometary nuclei, reconciles the compositional dishomogeneities observed on comets (the BPs) at macroscopic (up to tens of metres) scale, with a structurally homogeneous pebble-made nucleus at small (centimetre) scale, and with the processes determining the cometary activity at microscopic (sub-pebble) scales. Figure 1. 67P surface gets bluer approaching perihelion as a consequence of the progressive exposure to sunlight of subsurface WEBs (from Figure 4 in Ciarniello et al., 2022, Nature Astronomy, https://doi.org/10.1038/s41550-022-01625-y). The comet nucleus is made of two types of pebbles, both including refractories and CO2 ice, with different water ice content: pebbles with high content of H2O ice form the WEBs, while H2O-ice-poor pebbles represent the rest of the nucleus. CO2 ice is stable beneath the CO2 sublimation front at depths >0.1 m [12]. Approaching perihelion, the CO2 ice sublimation rate increases, eroding the surface by chunk ejection and exposing the WEBs. Once exposed, WEBs lose CO2 and are observable as BPs. Water-ice sublimation erodes the BPs ejecting sub-cm dust from their surface and preventing the formation of a dry crust [11]. The BPs survive until their water-ice fraction is sublimated, producing the observed surface blueing. Please refer to ref. [10] for complete details. References [1] Sunshine, J. M. et al. (2006) Science 311, 1453–1455. [2] Filacchione, G. et al. (2016) Nature 529, 368–372. [3] Raponi, A. et al. (2016) Mon. Not. R. Astron. Soc. 462, S476-S490. [4] Barucci, M. A. et al. (2016) Astron. Astrophys. 595, A102. [5] Oklay, N. et al. (2017) Mon. Not. R. Astron. Soc. 469, S582–S597. [6] Coradini, A. et al. (2007) Space Sci. Rev. 128, 529–559. [7] Keller, H. U. et al. (2007) Space Sci. Rev. 128, 433–506. [8] Fornasier, S. et al. (2016) Science 354, 1566–1570. [9] Filacchione, G. et al. (2020) Nature 578, 49-52. [10] Ciarniello, M. et al. (2022) Nat. Astron. doi:10.1038/s41550-022-01625-y. [11] Fulle, M. et al. (2020) Mon. Not. R. Astron. Soc. 493, 4039–4044. [12] Gundlach, B. et al (2020). Mon. Not. R. Astron. Soc. 493, 3690–3715. [13] Blum, J. et al. (2017) Mon. Not. R. Astron. Soc. 469, S755–S77. [14] O’Rourke, L. et al. (2020) Nature 586, 697–701. Acknowledgements We thank the Italian Space Agency (ASI, Italy; ASI-INAF agreements I/032/05/0 and I/024/12/0), Centre National d’Etudes Spatiales (CNES, France), and Deutsches Zentrum für Luft-und Raumfahrt (DLR, Germany) for supporting this work. VIRTIS was built by a consortium from Italy, France and Germany, under the scientific responsibility of IAPS, Istituto di Astrofisica e Planetologia Spaziali of INAF, Rome, which also led the scientific operations. The VIRTIS instrument development for ESA has been funded and managed by ASI (Italy), with contributions from Observatoire de Meudon (France) financed by CNES and from DLR (Germany). The VIRTIS instrument industrial prime contractor was former Officine Galileo, now Leonardo Company, in Campi Bisenzio, Florence, Italy. Part of this research was supported by the ESA Express Procurement (EXPRO) RFP for IPL-PSS/JD/190.2016. D.K. acknowledges DFG-grant KA 3757/2-1. This work was supported by the International Space Science Institute (ISSI) through the ISSI International Team "Characterization of cometary activity of 67P/Churyumov-Gerasimenko comet". This research has made use of NASA’s Astrophysics Data System.

The current generation of rovers exploring Mars for traces of life feature tools for subsurface sampling capabilities. This addition to the sampling capabilities of the martian rovers is crucial for the search for life. In fact, in the subsurface life is more likely to be protected from the harsh radiation environment present on the surface. The sampling of subsurface materials started with the analysis of the first millimeters of unweathered rocks being pulverized or abraded (NASA/MSL), evolved with the extraction of small cores from the first 10 centimeters (NASA/Mars2020), and will continue with the exploratory drilling of ESA's ExoMars 2022 which is capable of reaching 2 meters of depth. The proper planning and interpretation of measurements below the topographic surface require a model of the subsurface. Geological models are digital representations of subsurface structures generated by the sequence in time of processes putting in place different rocks and terrains. Geologic cross-sections are an example of bi-dimensional modeling that extends observations taken at the surface. Modern geologic models are commonly developed in three dimensions and used for terrestrial resource exploration, seismic analyses, and hydrologic simulations. The key to a good geologic model is the integration of measurements taken by different instruments. For ExoMars 2022, observations at the surface will be extended at depth by the spectrometer Ma_MISS which will read the mineralogical composition down to two meters, and the radar WISDOM which will collect geophysical images of the terrain down to ten meters or more. In this work, we explore different methods to generate geological models of the subsurface of areas at Oxia Planum and a selection of analog outcrops at different scales.

Summary Ceres is the largest object in the Solar System main belt. Clearly, Ceres experienced extensive water-related processes and geochemical differentiation and nowadays it is a body with a complex geological and chemical history [1]. Its surface is characterized by dark materials, phyllosilicates, ammonium-bearing minerals, carbonates, water ice, and salts. In addition to a global presence of carbon bearing chemistry, local concentration of aliphatic organics has been detected by Dawn [2]. In this context, we have started a series of laboratory spectroscopy measurements targeted to study the physicochemical interactions between organic material and minerals possibly present on Ceres. The goal is to understand the transformations induced on these samples by ultraviolet radiation, neutral atoms, and fast ions, under experimental conditions that simulate the environment of Ceres. The spectroscopic data obtained in laboratory experiments allow, through the comparison with the observations of the VIR spectrometer aboard the Dawn mission, to clarify the nature and origin of organic material identified on Ceres. Introduction Organic material in the minor bodies of the Solar System is an important component to understand planetary evolution and, eventually, the origin of life. Nevertheless, our knowledge on the subject is still limited. Recently the Dawn mission, thanks to the data collected by the Italian instrument VIR [3], showed clear evidence of a high amount of aliphatic organic material on the surface of Ceres [4, 5, 6] (Fig 1). This evidence has raised new questions about the origin and preservation of this material, especially when considering its high estimated abundance and the mineralogical context. Fig 1 Ceres spectra of the organic-rich area in Ernutet crater (label “Organics”); of a background organic-poor area from a region southeast of Ernutet (label “Background”); and of Occator bright material (label “Carbonate”) [4]. In order to understand the organic chemical species and in particular their abundance on Ceres, laboratory studies were performed [7]. The importance of having a direct comparison between laboratory and remote sensing data can provide a further investigation clues to shed light on the origin and evolution of Ceres. Through this project, we intend to study, through dedicated experiments, the interaction between minerals, water, and organic concerning the environmental conditions of Ceres. Making a synergistic use of complementary and indispensable skills present within INAF (Italian National Institute of Astrophysics) laboratories we investigated a complex issue such as that concerning the origin and preservation of organic molecules on planetary surfaces. Within INAF, complementary and unique realities coexist which, thanks to joint and coordinated work, can give a new interpretation of the physical-chemical processes active on Ceres. Project development and results In this study, we prepare mixtures of materials resembling the Ceres surface composition [8, 9] adding organic molecules in order to: (i) understand how organic molecules behave and eventually degrade on Ceres, in particular, how aliphatic molecules degrade by energetic processing with fast ions (keV-MeV) and UV photons [10, 11]. Moreover, the physico-chemical properties of the materials exposed to a flux of neutral atoms are investigated [12, 13]. (ii) evaluate the interaction between ammoniated minerals and simple organic molecules that may lead to the synthesis of complex compounds. In the presence of ultraviolet (UV) radiation, these minerals present on the surface of Ceres can show photocatalytic effects accelerating the photo-reactions, which generally destroy the original organic molecule and in the synthesis of new complex organic molecules [14]. (iii) evaluate the role of minerals in the protection or degradation of organic compounds. Some studies indicated a fundamental role of clays in the catalysis and preservation of organic materials [15]. Ceres is rich in clays and other hydrated minerals, making the interactions with the observed organics of particular interest. The project is carried out by several INAF institutes and laboratories. In detail: INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali prepared the analog mineral mixtures taking into account the compositional information gained by VIR observations. INAF - Osservatorio Astrofisico di Arcetri subsequently doped the mixture with several organic investigating UV photostability in Ceres analog conditions and the influence of temperature. INAF -Osservatorio Astronomico di Capodimonte studied irradiation with atoms and temperature effect while INAF - Osservatorio Astrofisico di Catania performed irradiation with fast ions. Finally, results of laboratory measurements were compared with data obtained by VIR instrument onboard Dawn mission. AcknowledgementsThis work is support by INAF Main Stream programme, grant 1.05.01.86.08 Evoluzione ed alterazione del materiale organico su Cerere (ref. Maria Cristina De Sanctis). References [1] De Sanctis et al., 2016, Nature 536, 54–57 [2] Marchi et al., Nature Astr., 2019 [3] De Sanctis et al., 2011, Space Science Reviews 163, 329-369. [4] De Sanctis et al., science 2017 355, 719 [5] Pieters et al., 2018, Meteoritics and Planetary Science 53 (9), 1983-1998 [6] De Sanctis et al., 2019, 482 (2), 2407–2421 [7] Vinogradoff et al., 2021 [8] Ferrari et al., 2019, Icarus 321, 522-530 [9]De Angelis et al., 2021 JGR Planets doi: 10.1029/2020JE006696 [10] Baratta et al. 2002, A&A, 384, 343-349 [11] Brucato et al. 2006, A&A, 455, 395-399 [12] Mennella et al. 2003, ApJ, 587, 727-738 [13] Palumbo et al 2004, Ad. Sp. Res., 33, 49-56 [14] Fornaro et al. 2013, Icarus, 226(1), 1068–1085 [15] Fornaro et al 2018, Astrobiology, 18, 989-1007

Introduction: The Dawn NASA mission investigated Ceres with its payload, including the Visual (0.25–1 μm) and InfraRed (1–5 μm) mapping spectrometer (VIR) [1]. The first findings from the VIR-IR channel confirmed some previous results from ground-based observations [2]: composition of surface includes a dark component (carbon and/or magnetite) and Mg-carbonates. The detection of a strong absorption at 2.7 μm was assigned to Mg-phyllosilicates; while the 3.06-μm absorption was attributed to NH4-phyllosilicates [3]. The elemental data from the GRaND instrument [4] provided additional constraints on the abundance of C, H, K, and Fe, [5,6], establishing that the dark material that makes up most of Ceres’ surface should be like carbonaceous chondrite [7,8]. The recent improvement in the VIR-VIS channel calibration [9,10] allows taking advantage of the full VIS spectral range. Following [9] and [10], IR channel calibration was also refined [9,10,11,12]. Data were photometrically corrected to standard viewing geometry using Hapke modeling [13] according to [14]. Thermal emission was removed [11]. The resulting spectrum is shown in Fig. 1. The VIR data have shown a clear absorption at 1 μm confirming previous ground observations [2]. The interpretation of such feature, in the context of the average spectrum of Ceres, provides new constraints on Ceres mineralogy. The 1μm feature: The 1-micron band that characterizes the average spectrum of ceres is also common in the spectra of several types of carbonaceous chondrites, (e.g., Ivuna CI, MAC87300 C2-ung, and DAV92300 CK4) (Fig. 2). Previous work [15,16,17] has suggested that these meteorites are characterized by the presence of mafic silicates and magnetite, which are often the main constituents of their fine-grained matrix in addition to low-crystallinity components. In the VIS-NIR range, the main bands of mafic silicates are between 0.9 and 1.1 μm. These absorption features are induced by Fe2+, whose coordination in the crystal structure determines the position of the bands. Ferrous oxides, such as magnetite, show very shallow absorption in the VIS-NIR range. Iron-containing carbonates also have a broad band near 1 μm, but they also show several other vibrational bands between 1.7 and 2.6 μm, allowing them to be distinguished from silicates and oxides. The near-1 μm band associated with the presence of iron is also evident in the spectra of low-crystallinity Fe-containing materials, such as tektites and volcanic glasses. In this case, the depth of the 1μm band varies depending on the amount of iron in octahedral coordination [18]. Mineralogical implications: The possible presence of magnetite on the surface of Ceres as one of the agents responsible for the low albedo of the dwarf planet may be supported by the mineral assemblage as detected by the VIR. Thus, the simultaneous presence of Mg-serpentine could suggest that most of the magnetite could have formed during the serpentinization process because of a serpentinization reaction [21]. The contemporaneous presence of magnetite and serpentine could disguise the spectral contribution of olivine, which may be present as a partially serpentinized primary crust. The occurrence of olivine has also been identified in laboratory heated serpentine and in heated carbonaceous chondrites [22,23]. These laboratory data show that the incipient crystallization of metamorphic olivine changes spectral properties by introducing a bump near 0.8 μm and a broad band near 1 μm, which resembles that observed in the average Ceres spectrum. This does not prove that Ceres experienced a high-temperature metamorphic process because the metamorphic olivine nucleation involves high temperatures that are inconsistent with the stability of ammonium hosted in clay minerals [24,25]. In this case, the presence of olivine could be an indication of a partial serpentinization process that affected the surface of Ceres. During the serpentinization process, the dissolution of olivine is also related to the formation of poorly crystalline phases [26] that represent metastable precursors of crystalline serpentine. Amorphous and nanocrystalline material has also been found in the matrix of several carbonaceous chondrites [27]. Spectral data obtained on mixtures of crystalline olivine and ferrous glass indicate that by increasing the content of the amorphous component, the band at 1 μm becomes shallower [28]. An additional complication in the interpretation of the 1 μm band in the average Ceres spectrum can be introduced by the presence of a fine-grained coating of iron-containing material that can introduce a spectral slope [29] consistent with the VIR data. Conclusions: Remnants of primary olivine, magnetite, and/or low-crystallinity iron phases may be responsible for the 1-μm band in Ceres' average spectrum. Further spectral modeling and laboratory activities will allow a better comprehension of this absorption feature giving important hints on the geological evolution of the dwarf planet. Acknowledgments: VIR data are available through the Planetary Data System (PDS) online data archive at:https://sbn.psi.edu/pds/resource/dawn/dwncvirL1.html. The VIR is funded by ASI and was developed under the leadership of INAF-IAPS. Selex-Galileo, Italy, built the instrument. The authors acknowledge the support of the Dawn Science, Instrument, and Operations Teams. This work was supported by ASIINAF n. I/004/12/0 and NASA. References: [1]De Sanctis MC et al SpaceSciRev (2011) [2]Rivkin AS et al SpaceSciRev (2011) [3]De Sanctis MC et al Nature (2015) [4]Prettyman TH et al SpaceSciRev (2011) [5]Prettyman TH Science (2017) [6]Prettyman TH et al 49th LPSC (2018) [7]Marchi S et al Nat Astron (2019) [8]Kurokawa H et al J Geophys Res Planets (2020) [9]Rousseau B et al Rev Sci Instrum (2019) [10]Rousseau B et al Astron Astrophys (2020) [11]Raponi et al Life (2021) [12]Carrozzo FG et al Rev Sci Instrum (2016) [13]Hapke B Theory of Reflectance and Emittance Spectroscopy Cambridge UK (1993) [14]Ciarniello M et al Astron Astrophys (2017) [15]King AJ et al Earth Planets and Space (2015) [16]Kallemeyn G W Meteoritics (1992) [17]Marlow R et al Antarct Met Newslett (1993) [18]Bell PM et al Proc 7th Lunar Sci Conf (1976) [19]Castillo‐Rogez J et al Meteorit Planet Sci (2018) [20]McSween HY et al Meteorit Planet Sci (2018) [21]Evans BW Geology (2010) [22]Hiroi T et al Antarct Met Res (1999) [23]Cloutis EA et al Icarus 221 (2012) [24]De Angelis et al JGR Planets (2021) [25]Bishop et al Planet Space Sci (2002) [26]King HE et al Environ Sci Tech (2010) [27]Abreu NM et al Microsc Microanal Suppl2 (2019) [28]Horgan BHN et al Icarus (2014) [29]Fisher EM Pieters CM Icarus (1993)

We describe the AMBITION project, a mission to return the first-ever cryogenically-stored sample of a cometary nucleus, that has been proposed for the ESA Science Programme Voyage 2050. Comets are the leftover building blocks of giant planet cores and other planetary bodies, and fingerprints of Solar System’s formation processes. We summarise some of the most important questions still open in cometary science and Solar System formation after the successful Rosetta mission. We show that many of these scientific questions require sample analysis using techniques that are only possible in laboratories on Earth. We summarize measurements, instrumentation and mission scenarios that can address these questions. We emphasize the need for returning a sample collected at depth or, still more challenging, at cryogenic temperatures while preserving the stratigraphy of the comet nucleus surface layers. We provide requirements for the next generation of landers, for cryogenic sample acquisition and storage during the return to Earth. Rendezvous missions to the main belt comets and Centaurs, expanding our knowledge by exploring new classes of comets, are also discussed. The AMBITION project is discussed in the international context of comet and asteroid space exploration.

The prominent bright deposit Cerealia Facula, Ceres, coincides with the central depression (or central pit) of the recently formed 92 km-wide complex crater Occator. The central pit is 9–10 km wide and up to 1 km deep and is partially filled with a 700 m-high 2 km-wide dome. The upper surface of the central dome is densely fractured but the flanks are not, indicating that uplift of the dome surface occurred after the bright deposit was emplaced, and primarily through uplift of the surface from below by laccolithic intrusion or volume expansion. The pit is rimless except for two prominent massifs that flank it to the east and west. This pit-dome morphology bears a strong resemblance in morphology, topography, and dimensions to central pit craters observed on Ganymede and Callisto, but is essentially absent on the similar sized ice-rich moons of Uranus, Saturn, and Pluto. The lack of pit craters on midsize icy moons and the possible lack of central pit craters at the cold poles of Ceres suggest that temperature is a significant controlling factor in central pit formation, beyond the canonical inverse-gravity scaling of complex crater transitions. While renewed modeling will benefit from these new constraints, the mapping of central pits on Ceres, including Occator, suggests that either the rheologically layered target model or more likely the melted central uplift model may be the most probable explanation for central pit formation on Ceres (lack of similar high-resolution imaging on the Galilean icy satellites precludes definitive evaluation of models there). Large volumes of lobate floor-fill material at least 600 m thick in some places cover large areas of the southern and eastern floor of Occator, and small outcrops of this unit are found perched high on closed topographic depressions on the Occator terrace zone and other higher areas of the crater floor. The swirling and knobby surface textures of these lobate deposits are essentially indistinguishable from those on impact melt sheets on large lunar craters such as Tycho. These observations indicate that this unit is most likely an impact melt sheet formed from melted water ice admixed with unmelted particulate or dissolved phyllosilicates, salts and/or carbonates, and large quantities of fragmented debris. Melt of ice phases within Ceres crust is also supported by independent numerical models of impact at Occator and would provide a ready source of fluids to promote hydrothermal deposition of the observed bright Na-carbonates on the surface of the central pit at Occator, if the deposit formed within a million years or so of impact. The central dome finds analogs in salt domes on Earth and pingos (frost-mounds) on Earth and Mars, which form by water and solute migration and freeze expansion. Later freezing of a central reservoir of volatiles beneath the central pit at Occator or mobilization of ice or other phases during the cooling and refreezing process could explain the uplift of the central dome. Finally, no changes were detected in the Cerealia and Vinalia Facula bright deposits during the course of the prime Dawn mapping mission, placing additional constraints on their formation time and limits on ongoing activity.

We studied the surface composition of Ceres within the limits of the Ezinu quadrangle in the ranges 180–270°E and 21–66°N by analyzing data from Dawn's visible and near-infrared data from the Visible and InfraRed mapping spectrometer and from multispectral images from the Framing Camera. Our analysis includes the distribution of hydroxylated minerals, ammoniated phyllosilicates, carbonates, the search for organic materials and the characterization of physical properties of the regolith. The surface of this quadrangle is largely homogenous, except for small, high-albedo carbonate-rich areas, and one zone on dark, lobate materials on the floor of Occator, which constitute the main topics of investigation. (1) Carbonate-rich surface compositions are associated with H2O ice rich crust. Weaker absorption bands of hydroxylated and ammoniated minerals over the carbonate-rich areas can be explained by higher abundances of carbonates at the topmost surface. (2) Dark, smooth lobate materials at the foot of Occator's northeastern wall possibly reveal fresh slumping of phyllosilicate-rich materials with fine grain size, or local enrichment in carbon-rich materials such as tholins. (3) The deeper absorption band depth of OH and NH4, on the rim of several impact craters, is one observation that is consistent with a stratification of the phyllosilicate abundance that has been inferred previously from global investigations.

We present an investigation of the emission intensity of CO2and H2O and their distribution in the coma of 67P/ Churyumov–Gerasimenko obtained by the VIRTIS-M imaging spectrometer on the Rosetta mission. We analyze 4 data cubes from Feb. 28, and 7 data cubes from April 27, 2015. For both data sets the spacecraft was at a sufficiently large distance from the comet to allow images of the whole nucleus and the surrounding coma. We find that unlike water which has a reasonably predictable behavior and correlates well with the solar illumination, CO2outgasses mostly in local regions or spots. Furthermore for the data on April 27, the CO2evolves almost exclusively from the southern hemisphere, a region of the comet that has not received solar illumination since the comet's last perihelion passage. Because CO2and H2O have such disparate origins, deriving mixing ratios from local column density measurements cannot provide a meaningful measurement of the CO2/H2O ratio in the coma of the comet. We obtain total production rates of H2O and CO2by integrating the band intensity in an annulus surrounding the nucleus and obtain pro-forma production rate CO2/H2O mixing ratios of ∼5.0% and ∼2.5% for Feb. 28 and April 27, respectively. Because of the highly variable nature of the CO2evolution from the surface we do not believe that these numbers are diagnostic of the comet's bulk CO2/H2O composition. We believe that our investigation provides an explanation for the large observed variations reported in the literature for the CO2/H2O production rate ratios. Our mixing ratio maps indicate that, besides the difference in vapor pressure of the two gases, this ratio depends on the comet's rotational orientation combined with its complex geometric shape which can result in quite variable rates of erosion for different surface areas such as the northern and southern hemisphere. Our annulus measurement for the total water production for Feb. 28 at 2.21AU from the Sun is 2.5×1026molecules/s while for April 27 at 1.76 AU it is 4.65×1026. We find that about 83% of the H2O resides in the illuminated portion of our annulus and about 17% on the night side. We also make an attempt to obtain the fraction of the H2O production coming from the highly active neck of the comet versus the rest of the illuminated surface from the pole-on view of Feb. 28 and estimate that about 60% of the H2O derives from the neck area. A rough estimate of the water surface evaporation rate of the illuminated nucleus for April 27 yields about 5×1019molecules/s/m2. Spatial radial profiles of H2O on April 27 on the illuminated side of the comet, extending from 1.78 to 6.47km from the nucleus center, show that water follows model predictions quite well, with the gas accelerating as it expands into the coma. Our dayside radial profile allows us to make an empirical determination of the expansion velocity of water. On the night side the spatial profile of water follows 1/ρ. The CO2profiles do not exhibit any acceleration into the coma but are closely matched by a 1/ρprofile.

Basaltic asteroids, known as V-types, are distributed throughout the main belt region. The greatest group of these objects is located in the inner main belt, constituting the Vesta family. However, in the last 20 years, many objects showing a basaltic composition have been identified also beyond 2.5 AU. These seem not to be related to (4) Vesta and require further investigation to better constrain their nature. We present the spectroscopic and dynamical investigation of 23 asteroids, 15 of which located in the middle and outer main belt regions. Results show that asteroids in these regions, confirmed as basaltic based on their spectra in the visible and near infrared, are more likely related to other asteroidal families, possibly differentiated. Introduction Basaltic material is reckoned as the result of an extensive geochemical differentiation, resulting in a body with a dense metallic core, a mantle of lighter olivine-rich material and an even lighter basaltic surface. This process should occur only on large-size objects, like (4) Vesta for instance, due to the heat needed to melt the chondritic material. The spectrum of (4) Vesta presents two deep absorption bands, at 0.92-0.94 μm and at 2.0μm, which are representative of pyroxenes. It also shows a very peculiar absorption band at 506 nm due to a forbidden transition of Fe2+. Most of the basaltic asteroids, identified through photometric measurements and then spectroscopically confirmed, are located in the inner main belt region (2.15-2.5AU) and mostly constitute the so-called Vesta family. This family counts more than 4500 members, only a small percentage of which have been spectrally characterised so far. These asteroids are indeed dynamically linked to Vesta (Milani et al. 2014) and share similar spectroscopic properties (Duffard et al. 2006; Moskovitz et al. 2010; De Sanctis et al. 2011; Migliorini et al. 2017). However, recent measurements allowed the identification of basaltic asteroids located beyond 2.5 AU (Lazzaro et al. 2000; Hardersen et al. 2004, 2018; Roig et al. 2008; De Sanctis et al. 2011; Solontoi et al. 2012; Ieva et al. 2018, Leith et al. 2017; Medeiros et al. 2019; Migliorini et al. 2017, 2021), which are unlikely related to Vesta, based on dynamical considerations. In addition, their surface composition shows some differences with respect to the V-types in the Vesta family region (see Jasmim et al. 2013). In the present work, we summarise the properties of basaltic asteroids, especially located beyond 2.5 AU, that were observed at Telescopio Nazionale Galileo (TNG) and ESO facilities during several observing runs. We also discuss their dynamical evolution, in relation to asteroid families that seem to be differentiated. Spectral analysis We have obtained vis and nir spectra of 23 asteroids, 15 of which located in the middle and outer main belt, selected as putative V-types according to vis and nir photometric surveys (Roig and Gil-Hutton 2006; Carvano et al. 2010; Licandro et al. 2017). Eight more asteroids in the inner main belt, non-belonging to the Vesta family, were observed for comparison reasons. Figure 1 shows the distribution of the observed asteroids in the proper semimajor axis-proper inclination plane. Sixteen asteroids show the pyroxene bands at 1 and 2 μm, confirming their basaltic nature. In addition, these all show the faint band at 506 nm, strengthening the composition of the so-called V-type asteroids. Of the asteroids in the middle and outer belt, 9 are confirmed as basaltic asteroids, while 3 are more compatible with Q- or S- complex. Fig. 1. Distribution of the observed asteroids in the inner, middle and outer main belt region. Observed asteroids are marked with black dots (in the inner main belt region), yellow diamonds (in the middle) and white squares (in the outer). Dynamical results The presence of basaltic asteroids far from the Vesta family region raises the question whether the V-type asteroids, observed all around the main belt, are indeed basaltic, like Vesta, or from some other bodies. In our work, the dynamics of a total of 14 asteroids in the middle main belt and 14 in the outer main belt (following Michtchenko et al. 2016), all confirmed as V-types was investigated. Among these objects, 7 were finally identified as either members or located nearby some families (Migliorini et al. 2021), whose parent body was probably differentiated or partially differentiated. This finding is in agreement with the hypothesis that V-types in the middle and outer regions have not been originated from (4) Vesta. In addition, this suggests that the number of differentiated objects in the middle and outer main belt must be much larger than previously assumed. Our work has contributed to enlarge the number of asteroids in the middle and outer main belt region, confirmed as basaltic, and successfully identified asteroidal families, which might contain basaltic asteroids. Acknowledgements Based on observations made with the VLT/X-shooter of the European Southern Observatory. This work is based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fondazione Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. This research was partly supported by the Italian Space Agency (grant DAWN-VIR n. I/004/12/0). References [1] Carvano J.M., et al., 2010, A&A, 510, A43. [2] De Sanctis M.C., et al., 2011, MNRAS, 412, 2318. 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