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The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos's along-track orbital velocity component of 2.70 +/- 0.10 mm/s, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg/m$^3$, we find that the expected value of the momentum enhancement factor, $\beta$, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg/m$^3$, $\beta$= 3.61 +0.19/-0.25 (1 $\sigma$). These $\beta$ values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos., Comment: accepted by Nature

Project Overview: Interest in Near-Earth Asteroids (NEAs) has rapidly grown in recent decades. The motivation is threefold: first, their proximity allows us to discover and investigate small bodies down to the metre-size, thus enhancing our understanding of the mechanisms underlying planetary formation; second, such information is also critical to mitigate their threat of collision with the Earth; third, their near-future exploitation can exponentially expand the natural resources available to humankind.Ground-based observations of thousands of NEAs have revealed the striking diversity existing within this population in terms of physical properties. So far, only a handful of NEAs have been visited by space missions: each of them provided unexpected discoveries and huge steps forward in our understanding of planetary sciences.Following the Near-Earth Space Trekker (NEST) proposal selected by ESA for the Phase 2 of the 2018 Call for a Fast mission, and the Asteroid Nodal Intersection Multiple Encounters (ANIME) proposal which passed the technical and financial screenings of the 2020 ASI Call for future CubeSat missions, here we propose to develop a flexible and modular concept, making use of smallsats and high-TRL available technology for the space exploration of several NEAs. Potential targets include Earth Trojan and other co-orbital asteroids, which are particularly appealing due to the low energetic cost to reach them. In particular, Earth Trojans represent a major gap in our inventory of near-Earth small bodies. Tracking their population size would put strong constraints on the dynamical and cosmochemical theories for the formation and evolution of the inner solar system.International Context: Deep-space smallsats represent a new frontier for the solar system exploration. After the success of the NASA/JPL Mars Cube One (MarCO) mission in 2018 and the launch of ASI LICIACube in November 2021 (currently hosted as piggyback of the NASA DART spacecraft, which will impact the binary NEA Didymos in September 2022), several further deep-space smallsat missions will take place in the next few years, e.g. in the framework of ESA HERA and NASA ARTEMIS I projects.Reference Scenario: Both CubeSat and larger SmallSat platforms are considered, which perfectly address the modularity and flexibility of the proposed mission concept. Multiple identical smallsats (to maximize mission return while minimizing costs and risks) can be launched profiting of the same or separate mission opportunities, and then reach their respective targets using electric propulsion and optimized interplanetary trajectories. Each smallsat will flyby and/or rendezvous multiple NEAs, with encounters at the nodal points.A preliminary selection of the targets has been performed assuming a 12U platform and mission durations capped at 2-3 years, with total ΔV < 3 km/s. We stress that the existence of a large number of sequences with similar performances outlines the strong implementation flexibility of our concept. Indeed, the definitive choice of target NEAs can be easily updated even at relatively late project phases, also considering the exponential growth of NEA discoveries. This gives us a huge flexibility in terms of mission scenarios, which can be adapted to varying constraints in terms of, e.g., launch date, propulsion specifics, mission architecture and duration.Example reference solutions that have been identified include the possibility to reach the Earth’s L4-L5 Lagrange points, using the smallsat payload for the discovery and characterization of Earth Trojan and co-orbital asteroids (especially those with a long synodic period relative to our planet, which are impossible to detect from Earth-based surveys), and to flyby already discovered Earth Trojan asteroids.Considered scientific payload (whose final selection will depend upon the choice of the platform) includes an optical camera, a near-infrared spectrometer, a mass spectrometer and a neutral particle camera, while the onboard transponder will be used to acquire radio science data.Technology Readiness: Mission architecture will rely on flight-proven (TRL 9) COTS and in-house components and scientific payload, using heritage from a number of ongoing (e.g., BepiColombo, LICIACube, …) or under development (e.g., Hera) space missions.Potentially selected components that have flown in the Earth orbital environment only will be appropriately shielded to ensure radiation tolerance to deep-space environment for the whole mission duration.Science and Technology Ambition: We aim to provide new insights into planetary science by characterizing several NEAs presenting peculiar and yet unexplored dynamical and physical properties. Noteworthy, such information will be also relevant for planetary protection purposes, as well as to assess a potential near-future exploitation of asteroid resources.We also aim to validate critical technologies for the exploitation of smallsats in solar system exploration, benefiting from the deep knowhow already gained by our team in designing and managing space missions to NEAs.Our mission concept relies on significant payload heritage and high-TRL available technology, based on our established consortium. Nevertheless, we will consider possible complementary contributions from further national and/or international partners willingly.

Introduction: Study of near-Earth objects (NEOs) is crucial to better understand the origin, formation and the evolution of the solar system. In particular, compositional, morphological and orbital characterisation of NEOs sheds light on the delivery of water and organics [1,2,3] to the prebiotic Earth, while ironically, some NEOs could be potential hazards for life on Earth [4]. In this context, we apply the G-mode multivariate statistical clustering method [5,6,7] on the orbital parameters of the currently available NEOs population, to probe potential associations with their spectral classification [8,9,10]. Data and Methods: G-mode method leads to an automatic statistical clustering of a sample containing N objects (NEOs in this case), described by M variables with the only control imposed by the user being the confidence level q1, expressed in terms of σ. The objects that cannot be associated to a cluster are separated and considered as outliers. We apply G-mode multivariate statistical clustering analysis to variables defining NEOs to determine clustering of objects. Our sample consists of 14132 NEOs, filtered based on their orbital uncertainty. Our input parameters to the G-mode method are twofold. First, in approach 1 (A1) we used three variables and their uncertainties as inputs: inclination (i), eccentricity (e) and semi-major axis (a) of the orbit. In approach 2 (A2) we used six inputs by including the argument of perihelion (ω), Tisserand parameter with respect to Jupiter (TJ) and the absolute magnitude (H) and their respective uncertainties in addition to those used in A1. Results: In A1, we obtained only one cluster at q1=3σ (accurate classification probability of 99.7%), which meant that the NEOs in this cluster are homogeneous in terms of the three orbital elements used. As we gradually lowered the value of q1, hence the confidence level, we noticed that more clusters got seeded and populated. We report in Table 1, mean parameter values with the median absolute deviation for 8 clusters obtained at q1=1.78σ. In addition to reporting the statistics of obtained clusters, we have also reported the outlier group of NEOs in the row indexed by 0. Among the reported clusters, cluster 1 (C1) corresponds to the background population of NEOs as their statistics are comparable to those of all hitherto discovered NEOs. C2 represents NEOs with relatively moderate inclination. C3, despite having relatively small number of NEOs, is constrained by well-behaved low-inclined, quasi-circular Earth-like orbits owing to their very low median absolute deviations. The very low mean H implies that these NEOs are relatively smaller with a distribution peak in the range of 5-15 meters of diameter. C5, C6 and C7 are of particular interest, for they could be associated with Jupiter-family cometary nuclei (2 < TJ < 3) as per their mean TJ. As such, the objects in these three clusters could potentially be extinct cometary nuclei. These clusters also have relatively higher eccentricities, akin to cometary orbits. We have checked available taxonomic classifications of NEOs [11,12,13] in the literature to get an insight into the composition of the objects. Although taxonomic classifications are not available for the majority of members in the clusters, we find that (i) C5 contains 3 C-types, 2 D-types and 0 S-types (ii) C6 contains 3 D-types and 4 S-types (iii) C7 contains 2 B-types, 3 C-types, 2 D-types and 1 S-type. Therefore we argue that C5 and C7 can be associated to primitive carbonaceous compositions while C6 can be associated to both carbonaceous and silicate-dominated compositions. To get more insights about the obtained G-mode clusters and further test these results, we applied a dynamic model to find their potential escape regions in the main belt [14]. This dynamical model, the Granvik model hereafter, traces with scrutiny the escape paths of objects from the main-belt to near-Earth space and the model accounts for the Yarkovsky effect [15]. Given the orbital elements and absolute magnitude of an NEO, it resolves a probability distribution function, built up of seven discrete values for seven escape regions. The results obtained with the Granvik model are shown in Fig. 1 for the clusters obtained for the G-mode run at q1=1.78σ in A1. Fig. 1. Probability distributions for the G-mode clusters obtained at 1.78σ for A1 to emanate from any of the seven escape regions. These results imply that most of the clusters have higher probability to emanate via ν6 secular resonance, known to be the most dominant escape path from the main-belt to the near-Earth space [16]. We observe that C5 and C7 have significant probabilities to emanate from outer-belt sources such as 2:1 mean motion resonance of Jupiter and JFCs. Thus, our dynamic modelling reinforces and corroborates existing results, pointing towards a primitive origin for the NEOs in these two clusters. Similiary, we will present the results of A2 and discuss their implications. Acknowledgements: We acknowledge the financial support from Agenzia Spaziale Italiana (ASI, contract No. 2017-37-H.0 CUP F82F17000630005) and funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870403. References: [1] Marty, B., Guillaume, A. et al. 2016, Earth and Planetary Science Letters, Volume 441,Pages 91-102 [2] Altwegg, K, Balsiger, H, Bar-Nun, A. et al. 2015, Science, Vol. 347,6220,1261952 [3] Ehrenfreund, P. & Sephton 2006, Faraday Discuss., The Royal Society of Chemistry,133,277-288 [4]Perna, D., Barucci M.A., Fulchignoni M. 2013, Astronomy and Astrophysics Review,Vol.21,65 [5] Barucci, M.A., Capria, M.T., Coradini, A. et al. 1987,Icarus,72,304 [6] Gavrishin, A.I., et al. 1992, Earth, Moon and Planets,59,141-152 [7] Barucci, M.A., Belskaya, I., Fulchignoni, M. et al. 2005,AJ130,1291 [8] Bus, S.J., & Binzel, R.P. 2002, Icarus,158,146 [9] DeMeo, F.E., Binzel, R. P., Slivan, S.M. & Bus, S. J. 2009,Icarus,202,160-180 [10] DeMeo, F.E., Alexander, C.M.O., Walsh, K.J.et al. 2015, Asteroids IV,13-41 [11] Perna, D., Barucci,M.A. et al. 2018, Planetary and Space Science,157,82-95 [12] Devogèle, M., Moskovitz, N. et al. 2019, The Astronomical Journal, American Astronomical Society,158,196 [13] Ieva, S., Dotto, E. et al. 2020,A&A,644,A23 [14] Granvik, M., Morbidelli, A., Jedicke, R., et al. 2018,Icarus,312,181 [15] Vokrouhlický, D., Bottke, W. F., Chesley, S.R., Scheeres, D.J., & Statler, T.S. 2015, in Asteroids IV,509–531 [16] Bottke, W.F., Morbidelli,A., Jedicke,R., et al. 2002,Icarus,156,399

Context. At present, near-Earth objects (NEOs) are being discovered at an ever-increasing rate. However, their physical characterisation is still significantly lagging behind. In particular, the taxonomic classification of newly discovered NEOs is of great importance with regard to improving our understanding of the population of NEOs. Aims. In this context, our goal is to probe potential links between orbital properties of NEOs and their composition. We investigate whether we can make a reasonable guess about the taxonomic class of an NEO upon its discovery with a decent orbital accuracy. Methods. We used a G-mode multivariate statistical clustering method to find homogeneous clusters in a dataset composed of orbital elements of NEOs. We adopted two approaches, using two sets of variables as inputs to the G-mode method. In each approach, we analysed the available taxonomic distribution of resulting clusters to find potential correlations with several unique parameters that distinctively characterise NEOs. We then applied a dynamical model on the same clusters to trace their escape regions. Results. Approach 1 (A1) led us to obtain NEO clusters that can be linked to a primitive composition. This result was further strengthened by the dynamical model, which mapped outer-belt sources as escape regions for these clusters. We remark on the finding of a cluster akin to S-type NEOs in highly eccentric orbits during the same approach (A1). Two clusters, one with small NEOs in terrestriallike orbits and one with relatively high inclinations, were found to be common to both approaches. Approach 2 (A2) revealed three clusters that are only separable by their arguments of perihelion. Taken altogether, they make up the majority of known Atira asteroids. Conclusions. For an NEO whose orbit is relatively well determined, we propose a model to determine whether the taxonomy of an NEO is siliceous or primitive if the orbital elements of the NEO fall within the presented combinations of inclination, eccentricity, and semi-major axis ranges.

Light Italian Cubesat for Imaging of Asteroids (LICIACube) is an Italian mission managed by the Italian Space Agency (ASI) and part of the NASA Double Asteroid Redirection Test (DART) planetary defense mission. Its main goals are to document the effects of the DART impact on Dimorphos, the secondary member of the (65803) Didymos binary asteroid system, characterizing the shape of the target body and performing dedicated scientific investigations on it. Within this framework, the mission Science Operations Center will be managed by the Space Science Data Center (ASI-SSDC), which will have the responsibility of processing, archiving, and disseminating the data acquired by the two LICIACube onboard cameras. In order to better accomplish this task, SSDC also plans to use and modify its scientific webtool Multi-purpose Advanced Tool for Instruments for the solar system Exploration (MATISSE), making it the primary tool for the LICIACube data analysis, thanks to its advanced capabilities for searching and visualizing data, particularly useful for the irregular shapes common to several small bodies.

The Light Italian Cubesat for Imaging of Asteroids (LICIACube) is part of the NASA Double Asteroid Redirection Test (DART), the first mission aiming to demonstrate the applicability of the kinetic impactor method for planetary defense. The mission was launched on 2021 November 24 to perform the impact experiment on Dimorphos, the small secondary of the binary asteroid (65803) Didymos. The 6U LICIACube, stored as a piggyback of the DART spacecraft, is the first Italian mission operating in deep space managed by the Italian Space Agency that will witness the effects of the DART impact on Dimorphos. On board LICIACube, there is a suite of cameras that will perform imaging of Didymos and Dimorphos to investigate the DART impact effects and study the binary system. Among them, the LICIACube Unit Key Explorer (LUKE), a wide-angle camera coupled to an RGB Bayer pattern filter, will be pivotal to constrain the surface composition and heterogeneity of the binary system due to differences in surface properties linked with possible space weathering effects and/or the presence of exogenous material. Multiband photometric analysis of LUKE data and laboratory experiments in support of data interpretation will provide new insights on the binary asteroid nature and evolution. Moreover, photometric phase curve analysis will reveal the scattering properties of the granular surface medium providing important constraints for the microphysical properties of the Didymos–Dimorphos system. In this work, we will present the state of the art of the LUKE scientific activities with an overview of the instrument setup, science operations, and expected results.

Introduction The study of near-Earth objects (NEOs) is crucial to better understand the origin, formation and the evolution of the solar system. In particular, compositional, morphological and orbital characterisation of NEOs sheds light on the delivery of water and organics [1,2,3] to the prebiotic Earth, while ironically, some NEOs could be potential hazards for life on Earth [4], as it has been witnessed in the past during impacts. Furthermore, these objects are also of interest for the future of humankind, for they could be useful as vital resources during interplanetary travel. Given this context, we apply the G-mode multivariate statistical clustering method [5,6,7] on the orbital parameters of the currently available NEOs population, to probe potential associations with their spectral classification [8,9,10]. Data and methods We apply the G-Mode multivariate statistical clustering analysis to selected orbital elements of NEOs to determine any dynamical clustering of objects. Once the clusters of objects are found, we proceed to investigate whether they have any correlations with spectral classes. The G-mode method leads to an automatic statistical clustering of a sample containing N objects (NEOs in this case), described by M variables (orbital elements) with the only control imposed by the user being the confidence level q1, expressed in terms of σ. Our sample consists of 10669 NEOs belonging to the dynamical groups Atiras, Atens, Apollos and Amors, available from the Minor Planet Center, filtered based on their orbital uncertainty (excluding those with an uncertainty parameter > 4). Our input parameters to the G-mode method are twofold. First, we use three variables: inclination (i), eccentricity (e) and semi-major axis (a) of the orbit as these are the main three parameters that define an orbit around the Sun. Secondly, we include three pseudo-parameters: mean orbital intersection distance with respect to the Earth (eMOID), perihelion distance (q) and aphelion distance (Q) of the orbit, in addition to the aforementioned three parameters, thus using six variables. Preliminary results Using i, e and a of the NEOs in our sample as inputs for G-mode, we obtain three clusters of NEOs at q1=1.9σ (with an accurate classification probability of 94.26%). The mean parameter values of each cluster with the median absolute deviation are given in Table 1. We have also reported some other parameters of interest, which include, Tisserand parameter with respect to Jupiter (TJ) and the absolute magnitude H. At this criterion, the vast majority of objects are clustered in the cluster #1. The cluster #2 with only 20 objects, appears interesting, as it is constrained by low-inclined, quasi-circular Earth-like orbits. The objects of the final cluster #3 are constrained by their relatively larger inclinations. We next used six variables: i, e, a, eMOID, q and Q as inputs for G-mode, while still holding q1 fixed at 1.9σ, in which case six clusters are found as reported in Table 2. Among the reported clusters, clusters #3,4 and 6 are of particular interest, for they could be associated with Jupiter-family cometary nuclei (2 < TJ < 3) as per their Tisserand parameter with respect to Jupiter. As such, the objects in these three clusters could potentially be extinct cometary nuclei. Interestingly, these clusters also have relatively higher eccentricities. We have checked available taxonomic classifications of NEOs [11,12,13] in the literature to get an insight into the composition of the objects found in our G-Mode clusters. Although taxonomic classifications are not available for the majority of members in the clusters, we find that (i) cluster #3 contains 4 C-type objects, (ii) cluster #4 contains 1 C-type, 2 D-type, 1 L-type, 5 S-type and 1 X-type objects, (iii) cluster #5 contains 1 B-type, 1 C-type, 1 T-type and 1 X-type objects. Apart from the S-type objects, the others usually have dark and red spectra indicative of primitive origin, which does not reject a cometary composition. We will augment this on-going study with more data and final results will be presented and discussed. Acknowledgements We acknowledge the financial support from Agenzia Spaziale Italiana (ASI, contract No. 2017-37-H.0 CUP F82F17000630005). We also acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870403. References [1] Marty, B., Guillaume, A. et al. 2016, Earth and Planetary Science Letters, Volume 441, Pages 91-102 [2] Altwegg, K, Balsiger, H, Bar-Nun, A. et al. 2015, Science, Vol. 347, Issue 6220, 1261952 [3] Ehrenfreund, P. & Sephton 2006, Faraday Discuss., The Royal Society of Chemistry, 133, 277-288 [4]Perna, D., Barucci M. A., Fulchignoni M. 2013, Astronomy and Astrophysics Review, Vol. 21,65 [5] Barucci, M.A., Capria, M.T., Coradini, A. et al. 1987, Icarus 72, 304 [6] Gavrishin, A. I., et al. 1992, Earth, Moon and Planets, 59, 141-152 [7] Barucci, M.A., Belskaya, I., Fulchignoni, M. et al. 2005, AJ 130, 1291 [8] Bus, S. J., & Binzel, R.P. 2002, Icarus 158, 146 [9] DeMeo, F. E., Binzel, R. P., Slivan, S. M. & Bus, S. J. 2009, Icarus, 202, 160-180 [10] DeMeo, F. E., Alexander, C. M. O., Walsh, K. J.et al. 2015, Asteroids IV, 13-41 [11] Perna, D., Barucci, M.A. et al. 2018, Planetary and Space Science, 157, 82-95 [12]Devogèle, M., Moskovitz, N. et al. 2019, The Astronomical Journal, American Astronomical Society, 158, 196 [13] Ieva, S., Dotto, E. et al. 2020, A&A, 644, A23

1. Introduction The JAXA Hayabusa2 mission probed the surface of the C-type asteroid (162173) Ryugu both with two touchdown operations to collect samples and return them to Earth, and with remote sensing instruments to characterize it at global scale. Among the payload of the spacecraft, the Near InfraRed Spectrometer (NIRS3) [1] is a point-spectrometer which acquired spectra in the 1.8-3.2 µm range of the asteroid surface to analyse its composition and detect possible heterogeneities. The surface of Ryugu has been shown to be uniformly dark (reflectance factor of 0.017 at 2.0 µm), slightly red-sloped and hydrated due to the presence of a weak, narrow absorption band at 2.72 µm attributed to Mg-phyllosilicates [2]. However, recent studies [3,4] using independent methods of analyses identified minor heterogeneities in the composition on Ryugu. 2. Data and methods Here we continue and expand such studies by selecting NIRS3 datasets that complement the investigated regions of the surface of Ryugu and/or improve the used spatial resolution. The dates corresponding to the datasets retained are the following (sorted by chronological order): July 19th 2018, October 30th 2018, February 28th 2019, July 25th 2019, July 26th 2019, July 27th 2019, October 8th 2019 and October 24th 2019. The coverage of each dataset on Ryugu is displayed in Figure 1. The data used for the analyses have been thermally corrected [2] and photometrically corrected [5]. The selected datasets are analysed using the G-mode multivariate statistical approach, using the same technique as in [3]. From a sample of N objects, each expressed by M variables, the code classifies each object in an homogeneous group with no other intervention from the user than the choice of the confidence level (labeled q and expressed in term of σ). The errors on each variable are taken into account in the classification. Further details on the method are available in [3,6]. 3. Preliminary results Preliminary results are shown from the analysis of the October 24th 2019 dataset only, which has the highest spatial resolution among the datasets we selected (7.66-9.67 m/footprint) and which covers the majority (~10°-~80°N) of the Northern hemisphere of Ryugu. Applying the G-mode with a confidence level of 2σ, and only on twenty-four selected wavelengths representative of the asteroid spectral properties, as in [3], we obtain four spectral groups. The mean spectra of each cluster are shown in Figure 2. The distribution of the four groups at the surface of Ryugu is presented in Figure 3. Group #1 contains almost 85% of the spectra, thus corresponding to the average spectral properties of Ryugu. Groups #2 to #4 can be attributed to the compositional heterogeneities. The mean spectra (Figure 2) are mainly separated according to their spectral slope between 2.05 and 2.61 µm. Groups #2 and #4 are the reddest (highest spectral slope), while group #3 is bluer (lower slope) than group #1. We also noted a slight variation for the 2.72 µm absorption band by computing its depth, groups #2 and #4 having the strongest band and group #3 the weakest. The distribution of the four groups on Ryugu (Figure 3) highlights interesting trends. Groups #2 and #4 seem to be concentrated around large craters (e.g. Cendrillon) and large depressions, such as the one located between 230° and 300° in longitude. On the contrary, group #3 appears inside this depression and in the region gathering large boulders between 200° and 230° in longitude. 4. Conclusion and perspectives We continue and expand previous clustering analyses of NIRS3 data by applying the G-mode algorithm to new datasets, which improve the spatial resolution and/or surface coverage of Ryugu. The preliminary results obtained for the Northern hemisphere of Ryugu are in overall good agreement with the previous findings for the equatorial region [3], confirming the presence of small heterogeneities on the surface. Moreover, they suggest that the material surrounding craters and depressions could present a redder spectral behaviour and a deeper band at 2.7 µm. The G-mode will be applied to all of the selected datasets (Figure 1). Selected regions of interest will also be investigated, notably the second Hayabusa2 touch-down region on which was dropped the Small Carry-on Impactor (SCI) to collect fresh material under the weathered surface [7], by analysing and comparing spectra of the area before and after the impact. Acknowledgements We thank the Haybusa2 JAXA team for their efforts in making the mission successful. Hayabusa2 was developed and built under the leadership of JAXA, with contributions from the DLR and the CNES, and in collaboration with NASA, Nagoya University, University of Tokyo, National Astronomical Observatory of Japan, Aizu University, Kobe University, and other universities, institutes, and companies in Japan. We would also wish to thank all the engineers who contributed to the success of the Hayabusa2 mission, especially T. Masuda, S. Yasuda, K. Matsushima, and T. Ohshima. We acknowledge financial support from ASI contract No. 2018-27-HH.0 “Partecipazione alla fase E della Missione Hayabusa2”. We also acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 870403. ED and JDPD thanks the financial support of the Agenzia Spaziale Italiana (ASI, contract No. 2017-37-H.0 CUP F82F17000630005). MA Barucci and M Fulchignoni acknowledge financial support by CNES. References [1] Iwata, T, et al.: NIRS3: The Near Infrared Spectrometer on Hayabusa2, Space Sci. Rev., 208, 317-337, 2017.[2] Kitazato, K, et al.: The surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy, Science, 364, 272-275, 2019.[3] Barucci, M. A., et al.: Multivariable statistical analysis of spectrophotometry and spectra of (162173) Ryugu as observed by JAXA Hayabusa2 mission, A&A, 629, 2019.[4] Matsuoka, M, et al.: Clustering analysis of NIRS3 infrared spectral data of Ryugu, 51st LPSC, LPI Contribution No. 2326, 2020.[5] Matsuoka, M, et al. (in preparation)[6] Gavrishin, A. I., et al.: Multivariate classification methods in planetary sciences, Earth, Moon and Planets, 59, 141-152, 1992.[7] Arakawa, M, et al.: An artificial impact on the asteroid (162173) Ryugu formed a crater in the gravity-dominated regime, Science, 368, 67-71, 2020.

Introduction Recent high-resolution ALMA observations of protoplanetary disks have raised interest in the study of solid bodies in disks at different scales, from sub-micrometric grains up to solid bodies hundreds of meters in size, for which dynamic evolution is governed by the interaction between the gas and the dust in the disk. We propose a novel research in the field of dust evolution and dynamics in protoplanetary disks. One of the main goals of this research is to address the dust dynamics evolution, the dynamical interaction between proto-planetary bodies, preparing the path for the SKA Key Programmes. We aim at contributing to this field twofold: (i) modeling of non-spherical dust dynamics in rarefied gas field present in the disk gaps and (ii) to interpret and reconstruct protoplanetary disk observations through numerical simulations, extending the PHANTOM code [1] to non-spherical dust setup, i. e. a particular focus is how the dynamics is influenced by dust dimension and shape. One of the main objectives is to reproduce the image of ALMA data and understand how different disk initial dust parameters and dust characteristics may influence the disk evolution and face-on or edge-on appearance. Using the state-of-the-art non-spherical dust dynamical model [2], developed for analysis of the ESA comet mission ROSETTA data, we determine the region in the gaps where the settling could occur as a function of the grain non-sphericity (shape, elongation), size, density etc. We investigate the terminal velocities and rotational frequencies of the non-spherical particles using different physical particle parameters, to show that the dust accommodation in the ring structures can be at distances different than what predicted by spherical dust models. The second focus of this work is to study the vertical settling with the SPH approach taking into account the dusty-gas interaction through the whole disk including possible planet-formation gaps. Dust dynamics models We use two models to simulate dust dynamics in protoplanetary disks: 1) a non-spherical dust dynamical model to simulate dust settling in Epstein regime and 2) the-state-of-the-art SPH code PHANTOM to simulate dust motion in both the Epstein and Stokes regimes. The first code is a 3D+t non-spherical dust model that solves the Euler dynamical and kinetic equations. Considering free-collisional dust regime we study the effects on the particle dynamics provided with different particle shapes, initial orientation and velocities, as well as torque. Torque is computed from the law of variation of the angular momentum by using the Euler dynamic equations. The particles are assumed to be homogeneous, isothermal convex bodies. The dust motion is governed by the gas drag and gravity of the host star and/or a planet in the gaps. The second model is a modified version of the PHANTOM code. We introduced non-spherical ellipsoidal particles and averaged drag coefficients for those non-spherical shapes. The code is a 3D+t SPH and MHD code and includes modules for self-gravity, dust-gas mixtures, viscosity, photo-evaporation, etc. A description of the parameters set used in these simulations with the results of simulations of dust settling are reported in Fig. 2. The plot is an example of dust settling in dusty disks, each of them having only one of three selected types of particles that are of the same mass and density, but of different shape. Dust settling with non-spherical particles Here we discuss two example cases produced by the two codes. Fig.1 shows rotational frequency (number of rotation per second) of two spheroids of different aspect ratio calculated with our non-spherical dust model in the Epstein regime. We simulate the dynamical properties and evolution of μm to mm sized particles in the case study with a planet in a disk gap at 60 AU, as observed in the HD163296 data [3, 4]. We assess the structure of the hypothesized vertically-extended dust layer. We investigated the influence of different dust sizes and initial dust speeds. Different spheroids of the same mass lead to different dynamics (e.g. velocity, angular velocity, etc) in the vertical settling phenomena. In the second group of simulations our non-spherical dust setup of the PHANTOM code has been used. By utilizing the pre-calculated averaged drag coefficients of spheroid particles in Epstein regime we simulated dust vertical settling in a disk using the SPH approach. The non-spherical dust particles in Epstein regime settle down slower than their spherical equivalent particles (see Fig 2). Moreover, the settling of larger non-spherical dust particles in Stokes regime shows a stratified structure: a denser sub-disk near the mid-plane for dust in Stokes regime and suspended particles in Epstein regime. Conclusions and future work We used two different models to simulate non-spherical dust settling in protoplanetary disks. The first one computes dusty-gas motion in Epstein regime using free molecular expression for rarefied field [1]. The second one uses a newly implemented feature of the state-of-the-art PHANTOM code, namely non-spherical dust shapes. Both models reveal that the interpretation of the ALMA observations can be biased by the spherical particle approximation. In our future work we will describe what we found applying the two dust models with non-spherical particles to study the dust evolution of edge-on disks. Usually the mm-sized particles settling in protoplanetary disks are aggregates of fractals formed from the dusty-gas interactions during the protostellar nebula phase. Such aggregates could be approximated with compact porous particles if dynamical (e.g. drag coefficients) and physical (e.g. porosity, density, fractal dimension) parameters are taken into account. Acknowledgments This research was supported by the National Institute for Astrophysics, Italy (INAF) within the Mainstream project “Non-spherical dust dynamics in protoplanetary disks - how realistic dust particle shapes change the dust evolution timescales”. References [1] Price D. J. et al. (2018), PASA 35, E031 [2] Ivanovski S. et al. (2017), Icarus 282, p. 333 - 350. [3] Isella et al. 2016, PRL, 117; [4] ALMA Partnership et al. 2015, ApJ Lett. 808:L3,10pp

著者人数: 66名 (所属. 宇宙航空研究開発機構宇宙科学研究所 (JAXA)(ISAS): 岩田, 隆浩; 安部, 正真; 大竹, 真紀子; 仲内, 悠佑; 松岡, 萌; L. Riu; 中藤, 亜衣子; 横田, 康弘; 坂谷, 尚哉; 山本, 幸生; 岡田, 達明; 澤田, 弘崇, 早川, 雅彦; 白井, 慶; 嶌生, 有理; 尾川, 順子; 照井, 冬人; 竹井, 洋; 佐伯, 孝尚; 中澤, 暁; 田中, 智; 吉川, 真; 渡邊, 誠一郎; 津田, 雄一), Accepted: 2019-03-07, 資料番号: SA1180385000

Analyses of meteorites and theoretical models indicate that some carbonaceous near-Earth asteroids may have been thermally altered due to radiative heating during close approaches to the Sun1–3. However, the lack of direct measurements on the subsurface doesn’t allow us to distinguish thermal alteration due to radiative heating from parent-body processes. In April 2019, the Hayabusa2 mission successfully completed an artificial impact experiment on the carbonaceous near-Earth asteroid (162173) Ryugu4,5, which provided an opportunity to investigate exposed subsurface material and test potential effects of radiative heating. Here we report observations of Ryugu’s subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. The strength and shape of the OH feature suggests that the subsurface material experienced heating above 300 °C, similar to the surface. In contrast, thermophysical modelling indicates that radiative heating cannot increase the temperature above 200 °C at the estimated excavation depth of 1 m, even at the smallest heliocentric distance possible for Ryugu. This supports the hypothesis that primary thermal alteration occurred on Ryugu’s parent body. Hayabusa2 created an artificial crater on Ryugu to analyse the subsurficial material of the asteroid. Results show that the subsurface is more hydrated than the surface. It experienced alteration processes that can be traced back to Ryugu’s parent body.

IntroductionAsteroid (65803) Didymos is an S-type [1] Apollo binary system characterized by a 780±30 m size primary, called Didymos, and a 164±18 m size secondary, called Dimorphos, orbiting at a distance of ~1.19 km [2]. The primary rotation period is 2.26 h [2], close to the 2.2 h disruption spin barrier [3], while the period of revolution of Dimorphos around the primary is 11.9217+0.0002 h [4]. This asteroid has been selected as the target of the Double Asteroid Redirection Test (DART, [5]), whose main goal is to impact Dimorphos at a speed of 6.6 km/s on September 30, 2022, thereby demonstrating the kinetic impactor technique and evaluating the resulting impulsive deflection.The scientific camera onboard DART is called DRACO, i.e. the Didymos Reconnaissance and Asteroid Camera for Op-nav [6]: its main goals are to image Didymos for optical navigation, to resolve the two bodies and support the spacecraft autonomous navigation to the target, and to locate the impact site precisely and characterize its local surface features. To complement such observations, the Light Italian Cubesat for Imaging of Asteroids (LICIACube, [7]) will be released from DART ten days before the impact, and autonomously guided through a flyby with closest approach distance of ~55 km from the target. LICIACube cameras LEIA (LICIACube Explorer Imaging for Asteroid - narrow angle camera) and LUKE (LICIACube Unit Key Explorer – wide angle camera) will then safely witness the redirection test in-situ, while its crater, as well as the ejecta and plume are being formed.Boulders SFD on Didymos systemBoulders/large blocks on asteroids are mainly interpreted as produced by target fragmentation and excavation due to high-velocity impact processes. They are the largest fragments excavated during an impact and are typically found within the crater or in its proximity, because they have not reached the escape velocity [8]. Instead, on rubble-pile asteroids boulders (typically the largest ones) are products of the reaccumulation process that formed the minor body itself, and may not be correlated to the observed craters [9]. For both cases, these blocks provide information on impact cratering processes occurring on low gravity bodies or on their parent body disruption event: their size-frequency distribution (SFD) fitting indices are therefore pivotal to provide hints on the fragment/boulder formation and/or degradation processes.Deriving boulder SFD and the corresponding power/exponential-law indices has been an important scientific topic addressed in several fly-by and orbital missions to minor bodies [e.g. 10-12]: it will be accomplished on the Didymos system as well.Four minutes before the impact the last image that contains all of Didymos will be taken by DRACO, with an expected spatial scale of 7 m/pixel. 120 seconds before impact, the last DRACO image containing any part of Dydimos will be taken, with a maximum resolution of 3.5 m [13]. DRACO will image all of Dimorphos ~50 cm/pixel ~17 seconds before impact and plans to return at least one higher-resolution image before impact. These final image(s) will have pixel scales At closest approach (CA), LICIACube/LEIA will image the surface of Dimorphos at 1.4 m/px [7]. If the DART crater will be observed through LEIA (it may be close to the limb during CA, hence the challenging imaging condition), we will be able to identify all boulders larger than 4.0-7.0 m located on the impacted side of Dimorphos, discerning those that have been generated/fragmented/moved after the DART impact from the ones previously imaged through DRACO. In addition, LEIA will image the non-impacted side of Dimorphos (not observed by DRACO) with resolutions ranging from 1.5 to 5 m: this will enable the characterization of the boulders SFD of the secondary down to 4.5 m.By comparing both the pre-, post- and non-impacted surface areas we will have the unique opportunity to witness how the boulders SFDs and densities/m2 will change as a result of a well characterized, hypervelocity impact. We will therefore test if the generation of a crater results in a different power-law distribution of boulders than the one observed on other S-type asteroids, such as (433) Eros and (25143) Itokawa [8,9], as well as recently observed carbonaceous asteroids, (101955) Bennu [12] and (162173) Ryugu [15].Acknowledgments: This research was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0).References: [1] de León, J. et al. (2010) Astron. Astrophys, 517, A23. [2] Naidu, S.P. et al. (2020) Icarus, 348, 113777. [3] Pravec P. and Harris A.W. (2000) Icarus, 148, 12-20. [4] Pravec, P. et al. (2006) Icarus, 181, 63. [5] Cheng A. F. et al. (2016) Planet. Space Sci., 121, 27-35. [6] Fletcher, Z.J. et al. (2016) 3rd Inst. Planetary Missions, 4043. [7] Dotto, E. et al., (submitted), Planet. Space Sci. [8] Thomas, P.C., et al. (2001) Nature 413, 394. [9] Michikami, T. et al. (2008), Earth Planets Space, 60, 13-20. [10] Lee, S.W., et al. (1986) Icarus 68, 77. [10] Geissler, P., et al. (1996) Icarus 120, 140. [11] Pajola, M. et al. (2015), Astron. Astrophys. 583, A37. [12] DellaGiustina, D. et al. (2019), Nat.Astron. 3, 341-351. [13] Cheng, A. F. et al. (2018) Planet. Space Sci., 157, 104-115. [14] Barnouin, O. et al. (2019). LPSC 50 abst. 2448. [15] Watanabe, S. et al. (2019), Science, 364, 6437, 268-272.

The research about Near Earth Objects (NEOs) is a major topic in planetary science. One reason is the potential hazard some of them pose to human beings and, more in general, to life on our planet. Moreover, the physical characterization of NEOs allows us to put constraints on the material accreted in the protoplanetary nebula at different solar distances and can give us insights into the early processes that governed the formation and the evolution of planets - including the delivery of water and organics to Earth -, and into further evolutionary processes that acted on asteroid since their formation - such as collisions and non-gravitational effects. The “NEOROCKS - The NEO Rapid Observation, Characterization and Key Simulations” Collaborative Research Project has been recently approved to address the topic c) “Improvement of our knowledge of the physical characteristics of the NEO population” of the call SU-SPACE-23-SEC-2019 from the Horizon 2020 - Work Programme 2018-2020 Leadership in Enabling and Industrial Technologies – Space. The aims of NEOROCKS are: to develop and validate advanced mathematical methods and innovative algorithms for NEO orbit determination and impact monitoring; to organize follow-up astronomical observations of NEOs efficiently, in order to obtain high-quality data needed to derive their physical properties, giving priority to timely addressing potentially hazardous objects; to improve dramatically statistical analysis, modelling and computer simulations aimed to understand the physical nature of NEOs, focussing on small size objects, which are of uttermost importance for designing effective impact mitigation measures in space and on the ground; to ensure maximum visibility and dissemination of the data beyond the timeline of the project, by hosting it in an existing astronomical data center facility; to foster European and international cooperation on NEO physical characterization, providing scenarios and roadmaps with the potential to scale-up at a global level the experience gained during the project; to apply and guarantee continuity of educational and public outreach activities needed to improve significantly public understanding and perception of the asteroid hazard, counteracting the spreading of “fake news” and unjustified alarms. Acknowledgement: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870403 (project NEOROCKS).

Introduction On September 30, 2022, NASA’s Double Asteroid Redirection Test (DART, [1]) mission will be the first space mission demonstrating the kinetic impactor method for planetary defense. DART will impact Didymos B (a 164±18 m secondary of asteroid (65803) Didymos [2]) with its mass of 650 kg and at a speed of 6.6 km/s. Such impact is expected to change the secondary orbital period by about 10 minutes. DART will carry as a piggyback the Light Italian Cubesat for Imaging of Asteroids (LICIACube, [3]) which will be released from DART ten days before the impact. LICIACube will provide evidence of the impact and will take multiple images of the target up to a distance of ~55 km from the target. The LICIACube narrow and wide angle cameras - LEIA (LICIACube Explorer Imaging for Asteroid) and LUKE (LICIACube Unit Key Explorer), respectively – will capture the post-impact processes coming from in situ events, such as the newly formed crater, the expanding ejecta and the dynamics of its plume. In particular, the measurement of the motion of the slow ( Dust plume model We use a 3D+t non-spherical dust model that solves the Euler dynamical and kinetic equations. Considering free-collisional dust regime we study the effects on the particle dynamics provided with different shapes, initial particle orientation and velocities as well as torque. Torque is computed from the law of variation of the angular momentum by using the Euler dynamic equations. The particles are assumed to be homogeneous, isothermal convex bodies, having the same physical properties of the target. The dust motion is governed by solar radiation pressure force, initial dynamical parameters (speed, orientation and torque) and gravity of the asteroid binary system. To compute the gravity we take into account that Didymos B is orbiting at distance of ~1.18 km the Didymos primary (780±80 m in size) [6]. As input we use the physical parameters obtained via numerically simulated impact into low-gravity and strength- dominated asteroid surface done with the iSALE numerical code [5]. A detailed description of the parameters set used in the impact modelling are reported in Table 1. As an example, in Fig.1, we show the iSALE simulation of the spatial distribution of tracer particles for 50 ms after the impact. Table 1: Paremeters used for iSAle simulation. A detailed description can be found in [5]. Fig. 1: A snapshot of the formation of the crater resulting from the iSALE modelling performed with parameters reported in Table 1. The colorbar represent the peak pressure of the ejecta tracer particles. Non-spherical dust motion in the plume We have studied the motion of non-spherical particles after the impact assuming various set of initial parameters coming from the iSALE simulations, such as particle mass, shape, initial orientation, launch position and computed velocity. The Didymos system physical parameters and particle temperature were taken from [7]. Here, in Fig. 2, we show the velocity and the distance from the surface where it has been reached for a prolate spheroid (aspect ratio = 2 [4]) with assumed density 2600 kg/m3. The particle mass is 7.45 x10-2 kg, the initial velocity 0.94 m/s, the launch position is 11 m from the center of the crater and the initial tilt of the initial velocity vector away from local surface normal is 46 degrees. We plotted the results for two cases: 1) only the Didymos B gravity field is considered and 2) the gravity of the whole binary is used. Our results show that the particle dynamics is sensitive to parameters such as orientation and ejection velocity. Fig. 2: Velocity and distance at which it has been achieved for a prolate particle (aspect ratio a/b = 2). The complete set of parameters is given in the text. The solid line indicates the case when only gravity of Didymos B was considered and the dashed line when the gravity of the whole binary was used (binary was approximated as a mass point). This study of dust dynamics in expanding ejecta together with LICIACube plume evolution images can further constrain the momentum transfer efficiency estimation as well as the ejecta velocity and dust size distribution in the “far-field” expanding plume. Acknowledgments This research was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0). References [1] Cheng A. F. et al. (2016) Planet. Space Sci., 121, 27-35. [2] de León, J. et al. (2010) Astron. Astrophys, 517, A23. [3] Dotto, E. et al., (submitted), Planet. Space Sci. [4] Ivanovski S. et al. (2017), Icarus 282, p. 333 - 350. [5] Raducan, S. D. et al. (2019), Icarus, 329, p. 282 - 295. [6] Michel, P. et al. (2016) Adv. Space Sci. 57, p. 2529 - 2547. [7] Yu Y. et al. (2017), Icarus 282, p.313 - 325

In Autumn 2022, the NASA Double Asteroid Redirection Test Mission (DART) will impact the surface of asteroid Dimorphos, a ~165 m body orbiting around asteroid (65803) Didymos, with the main aim to demonstrate the kinetic impactor technique for Planetary Defense. During the last minutes of the mission, the DRACO scienti c camera onboard DART will image the surface of both the primary and the secondary asteroids at different spatial scales, allowing the detection of boulders larger than 0.6-1.5 m on the impacted side of Dimorphos and larger than 11-21 m on Didymos. To complement such observations, the ASI "Light Italian Cubesat for Imaging of Asteroids" (LICIACube) will be released from DART ten days before the impact and will be then autonomously guided through a yby with closest approach distance of 55 km from Dimorphos. Through the LEIA (LICIACube Explorer Imaging for Asteroid) narrow angle camera, it will be possible to safely witness the DART redirection test in situ, while its crater and the ejecta and plume are being formed. At closest approach LEIA will image Dimorphos at ~2 m/px: we will therefore be able to identify all boulders larger than 4-7 m located on the imaged side of the asteroid. The analysis of the boulder surface densities and size frequency distributions (SFD) on Didymos and Dimorphos will be important to understand the processes that originated them (impact cratering versus parent body disruption). In addition, we will compare the SFD derived on the binary asteroid with those obtained on other S-type or carbonaceous minor bodies, highlighting the similarities and differences. In this work, the results of the boulder SFD expected from both LICIACube and DART images are presented. Acknowledgments: This research was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0).

Asteroid (65803) Didymos is an S-type [1] Apollo binary system characterized by a 780±30 m size primary, called Didymos, and a 164±18 m size secondary, called Dimorphos, orbiting at a distance of ~1.19 km [2]. The primary rotation period is 2.26 h [2], close to the 2.2 h disruption spin barrier [3], while the period of revolution of Dimorphos around the primary is 11.9217+0.0002 h [4]. This asteroid has been selected as the target of the Double Asteroid Redirection Test (DART, [5]), whose main goal is to impact Dimorphos at a speed of 6.6 km/s on September 30, 2022, thereby demonstrating the kinetic impactor technique and evaluating the resulting impulsive deflection. The scientific camera onboard DART is called DRACO, i.e. the Didymos Reconnaissance and Asteroid Camera for Op-nav [6]: its main goals are to image Didymos for optical navigation, to resolve the two bodies and support the spacecraft autonomous navigation to the target, and to locate the impact site precisely and characterize its local surface features. To complement such observations, the Light Italian Cubesat for Imaging of Asteroids (LICIACube, [7]) will be released from DART ten days before the impact, and autonomously guided through a flyby with closest approach distance of ~55 km from the target. LICIACube cameras LEIA (LICIACube Explorer Imaging for Asteroid - narrow angle camera) and LUKE (LICIACube Unit Key Explorer - wide angle camera) will then safely witness the redirection test in-situ, while its crater, as well as the ejecta and plume are being formed.

Context. The near-Earth objects (NEOs), whose proximity makes them the most accessible bodies in the Solar System, allow us to sample asteroids from tens of kilometers down to objects of a few meters in size. However, while the physical properties for the largest bodies are mostly known, we have very little physical information regarding the small NEOs. These objects today represent the overall majority among the ~2500 new discoveries each year, but they are usually only bright enough to be observable during their close approaches. Aims. Our aim was to extend our survey that started in 2015 on the NEO population, using ground-based observations to characterize the fainter (and typically smaller) NEOs observable each night. Methods. We performed BVRIz photometry of NEOs, making use of the DOLORES instrument at the Telescopio Nazionale Galileo (TNG, La Palma, Spain) and the Asiago Schmidt telescope (Italy), in order to derive visible color indexes and the taxonomic classification for each target in our sample. Results. We taxonomically classified 51 new NEOs for the first time. Together with data obtained in our previous work and collected by other surveys available online, we analyzed an extended sample of 1081 individual NEOs. While the overall majority of them belong to the S-complex, our analysis of the taxonomic distribution found a larger contribution for dark bodies going toward larger H, suggesting that they could be more abundant among the fainter NEOs. Moreover, we find an interesting correlation between semi-major axis and diameter, which could be in part related to the Yarkovsky effect. Rapid characterization of the fainter NEO population shortly after their discovery will be crucial in the future, before those bodies become too faint to be observed, or lost forever.

Full list of authors: Cremonese, G.; Capaccioni, F.; Capria, M. T.; Doressoundiram, A.; Palumbo, P.; Vincendon, M.; Massironi, M.; Debei, S.; Zusi, M.; Altieri, F.; Amoroso, M.; Aroldi, G.; Baroni, M.; Barucci, A.; Bellucci, G.; Benkhoff, J.; Besse, S.; Bettanini, C.; Blecka, M.; Borrelli, D.; Brucato, J. R.; Carli, C.; Carlier, V.; Cerroni, P.; Cicchetti, A.; Colangeli, L.; Dami, M.; Da Deppo, V.; Della Corte, V.; De Sanctis, M. C.; Erard, S.; Esposito, F.; Fantinel, D.; Ferranti, L.; Ferri, F.; Ficai Veltroni, I.; Filacchione, G.; Flamini, E.; Forlani, G.; Fornasier, S.; Forni, O.; Fulchignoni, M.; Galluzzi, V.; Gwinner, K.; Ip, W.; Jorda, L.; Langevin, Y.; Lara, L.; Leblanc, F.; Leyrat, C.; Li, Y.; Marchi, S.; Marinangeli, L.; Marzari, F.; Mazzotta Epifani, E.; Mendillo, M.; Mennella, V.; Mugnuolo, R.; Muinonen, K.; Naletto, G.; Noschese, R.; Palomba, E.; Paolinetti, R.; Perna, D.; Piccioni, G.; Politi, R.; Poulet, F.; Ragazzoni, R.; Re, C.; Rossi, M.; Rotundi, A.; Salemi, G.; Sgavetti, M.; Simioni, E.; Thomas, N.; Tommasi, L.; Turella, A.; Van Hoolst, T.; Wilson, L.; Zambon, F.; Aboudan, A.; Barraud, O.; Bott, N.; Borin, P.; Colombatti, G.; El Yazidi, M.; Ferrari, S.; Flahaut, J.; Giacomini, L.; Guzzetta, L.; Lucchetti, A.; Martellato, E.; Pajola, M.; Slemer, A.; Tognon, G.; Turrini, D. -- This is an open access article, The SIMBIO-SYS (Spectrometer and Imaging for MPO BepiColombo Integrated Observatory SYStem) is a complex instrument suite part of the scientific payload of the Mercury Planetary Orbiter for the BepiColombo mission, the last of the cornerstone missions of the European Space Agency (ESA) Horizon + science program. The SIMBIO-SYS instrument will provide all the science imaging capability of the BepiColombo MPO spacecraft. It consists of three channels: the STereo imaging Channel (STC), with a broad spectral band in the 400-950 nm range and medium spatial resolution (at best 58 m/px), that will provide Digital Terrain Model of the entire surface of the planet with an accuracy better than 80 m; the High Resolution Imaging Channel (HRIC), with broad spectral bands in the 400-900 nm range and high spatial resolution (at best 6 m/px), that will provide high-resolution images of about 20% of the surface, and the Visible and near-Infrared Hyperspectral Imaging channel (VIHI), with high spectral resolution (6 nm at finest) in the 400-2000 nm range and spatial resolution reaching 120 m/px, it will provide global coverage at 480 m/px with the spectral information, assuming the first orbit around Mercury with periherm at 480 km from the surface. SIMBIO-SYS will provide high-resolution images, the Digital Terrain Model of the entire surface, and the surface composition using a wide spectral range, as for instance detecting sulphides or material derived by sulphur and carbon oxidation, at resolutions and coverage higher than the MESSENGER mission with a full co-alignment of the three channels. All the data that will be acquired will allow to cover a wide range of scientific objectives, from the surface processes and cartography up to the internal structure, contributing to the libration experiment, and the surface-exosphere interaction. The global 3D and spectral mapping will allow to study the morphology and the composition of any surface feature. In this work, we describe the on-ground calibrations and the results obtained, providing an important overview of the instrument performances. The calibrations have been performed at channel and at system levels, utilizing specific setup in most of the cases realized for SIMBIO-SYS. In the case of the stereo camera (STC), it has been necessary to have a validation of the new stereo concept adopted, based on the push-frame. This work describes also the results of the Near-Earth Commissioning Phase performed few weeks after the Launch (20 October 2018). According to the calibration results and the first commissioning the three channels are working very well. © 2020, The Author(s)., We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0. The SIMBIO-SYS instrument has been developed by Leonardo under ASI contract I/054/10/0.

The aim of this paper is to report on the results of a multicolour observing campaign performed at the LBT on the interstellar comet 2I/Borisov during three epochs while target was approaching its perihelion: UBVRI images have been observed in October and December 2019, when the comet was at ∼2.3 and 2.0 au from the Sun, respectively. Comet Borisov presented a rather complex morphology, especially in the December observing epoch, when a bi-lobate structure on a global scale was visible, with a jet-like structure characterised by a disconnection event, probably due to the presence of an active area on the nucleus' surface combined with its rotational properties. U – B colour, measured for the first time for this comet, monotonically decreases as Borisov approaches perihelion, from 0.35 ± 0.05 in October 19th to −0.07 ± 0.05 in December 2nd; B – V colour shows a more chaotic behaviour, with values for October epochs quite similar to solar colours, and a higher value of 0.76 ± 0.04 in December 2nd, probably due to a combination of an increase of the B flux (CN emission) and of an increase in V flux (due to C2). V – R and R–I colours derived in both the October and December observing epochs depict a scenario of a coma slightly redder than the Sun, with a RI-reddening value of ∼11%/1000 A and ∼5%/1000 A, respectively. The R- Afρ at the reference aperture of r ∼104 km from the optocentre slightly decreases from ∼100 cm (October) to ∼ 70 cm (December), showing that the Borisov's dust environment is quite similar to those of Short Period Comets of our Solar System. The application of a first-order photometric model, with the plausible scenario of grains with radius a = 100 μm and bulk density ρd = 1000 kg/m3 moving at vd in the range of 3–30 m/s, allows to derive a dust production rate Qd decrease from a range of 3–25 kg/s in October to a range of 2–18 kg/s in December. All these results confirm that the interstellar comet 2I/Borisov has a coma environment quite similar to that of the Short Period Comets (mostly Jupiter Family targets) orbiting in our inner Solar System.

International audience

Table A.1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A46, Aims. We studied the rotational properties of the dwarf planet Makemake. Methods. The photometric observations were carried out at different telescopes between 2006 and 2017. Most of the measurements were acquired in BVRI broad-band filters of a standard Johnson-Cousins photometric system. Results. We found that Makemake rotates more slowly than was previously reported. A possible lightcurve asymmetry suggests a double-peaked period of P = 22.8266 ± 0.0001 h. A small peak-to-peak lightcurve amplitude in R-filter A = 0.032 ± 0.005 mag implies an almost spherical shape or near pole-on orientation. We also measured BVRI colours and the R-filter phase-angle slope and revised the absolute magnitudes. The absolute magnitude of Makemake has remained unchanged since its discovery in 2005. No direct evidence of a newly discovered satellite was found in our photometric data; however, we discuss the possible existence of another larger satellite.© ESO 2019, J.L.O., R.D., and P.S.-S acknowledges financial support from the State Agency for Research of the Spanish MCIU through the >Center of Excellence Severo Ochoa> award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). Funding from MINECO project AYA2017-89637-R is acknowledged. Part of the research leading to these results has received funding from the European Union's Horizon 2020 Research and Innovation Programme, under Grant Agreement no 687378, as part of the project >Small Bodies Near and Far> (SBNAF). R.Ya.I., V.R.A., and V.T.Z. are grateful to the Shota Rustaveli National Science Foundation grant FR-18-1193 for the partial financial support. D.P. has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement n. 664931. I.V.R. and A.V.S. were partly supported by the programme BR05236322 of the Ministry of Education and Science of the Republic of Kazakhstan and the scientific and technical program BR05336383 >Applied scientific research in the field of space activities>.

“LICIACube – the Light Italian Cubesat for Imaging of Asteroids” is managed by the Italian Space Agency (ASI) and will be part of the NASA DART mission, with the aim of i) documenting the DART impact’s effects on the secondary member of the (65803) Didymos binary asteroid system, ii) characterizing the shape of the target, and iii) performing dedicated scientific investigations on it. DART probe will be launched at the end of 2021 and LICIACube will be hosted as piggyback during the interplanetary cruise, then released 10 days before the impact, and autonomously guided along its fly-by trajectory. The LICIACube payload is composed by LEIA, a narrow FoV camera, and LUKE, a wide FoV imager with an RGB Bayer pattern filter, that will collect and transmit to Earth several unique images of the effects of the DART impact on the asteroid, such as the formation and the development of the plume potentially determined by the impact. LICIACube will be the first deep space mission developed and autonomously managed by an Italian team: the design, integration and test of the CubeSat have been assigned by ASI to the aerospace company Argotec, while the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Center, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center. The LICIACube team includes a wide Italian scientific community, involved in the definition of all the aspects of the mission: trajectory design; mission definition (and real-time orbit determination during operations); impact, plume and imaging simulation and modelling, in preparation of a suitable framework for the analysis and interpretation of in-situ data. The major technological mission challenge, i.e. the autonomous targeting and imaging of such a small body during a fast fly-by, to be accomplished with the limited resources of a CubeSat, is affordable thanks to a strong synergy of all the mentioned teams in support of the engineering tasks.

The near-Earth object (NEO) population is a window into the original conditions of the protosolar nebula, and has the potential to provide a key pathway for the delivery of water and organics to the early Earth. In addition to delivering the crucial ingredients for life, NEOs can pose a serious hazard to humanity since they can impact the Earth. To properly quantify the impact risk, physical properties of the NEO population need to be studied. Unfortunately, NEOs have a great variation in terms of mitigation-relevant quantities (size, albedo, composition, etc.) and less than 15% of them have been characterized to date. There is an urgent need to undertake a comprehensive characterization of smaller NEOs (D, 10 pages, 3 figures, accepted to A&A

The Near-Earth Object (NEO) population, being the remnants of the building blocks that originally formed our solar system, allows us to understand the initial conditions that were present in the protosolar nebula. Its investigation can provide crucial information on the origin and early evolution of the solar system, and shed light on the delivery of water and organic-rich material to the early Earth. Furthermore, the possible impact of NEOs poses a serious hazard to our planet. There is an urgent need to undertake a comprehensive physical characterization of the NEO population, particularly for the ones with the higher likelihood of catastrophic impact with the Earth. One of the main aims of the NEOShield-2 project (2015-2017), financed by the European Commission in the framework of the HORIZON 2020 program, is to undertake an extensive observational campaign and provide a physical and compositional characterization for a large number of NEOs in the < 300 m size range, retrieving in particular their mitigation-relevant properties (size, shape, albedo, diameter, composition, internal structure, ...) in order to design impact mitigation missions and assess the consequences of an impact on Earth. We carried out visible photometric measurements for a sample of 158 uncharacterized NEOs. We also made use of visible and near-infrared spectroscopy to assess NEO composition and perform a mineralogical analysis. We found that carbonaceous C-complex asteroids deserve a special attention, since their physical structure (e.g., primitive nature, porosity) and their orbital parameters (mainly the inclination) make at the moment challenging the design of a successful mitigation strategy. Indeed, the most advanced mitigation technique (the kinetic impactor) is less effective on these bodies, and the high inclination of some possible impactors require a launch vehicle capability beyond the one currently available.

P/2004 A1 (LONEOS) is one of the few active objects in the dynamical class of Centaurs. It has been recently injected into an inner orbit with a perihelion distance q = 5.5 au. The aim of this paper is to characterize the dust coma of this peculiar object, 2.5 yr after its first ‘new’ perihelion passage inside the Solar system. Broad-band visible images taken at the TNG telescope in 2007 February were analysed in order to characterize the dust coma of the Centaur: it was still quite active at rh = 6.5 au post-perihelion, with a coma and a well-developed wide tail-like structure, with a measured R-Afρ= 162 ± 10 cm in an aperture radius ρ= 104 km. The (V − R) colour and the reddening values depict a scenario of a slightly red dust coma. A dust mass-loss rate of = 133 kg s−1 is derived from a photometric model, consistent with a scenario of a quite constant emission rate along the Centaur orbit. An upper limit for the Centaur radius of 3.5 km is derived by some realistic hypotheses on CO molecular production rate and on the mean grain scatterer size in the coma. Dynamical lifetime estimates compared to modelled loss rate result in a radius lower limit of 0.5 km, indicating therefore that the Centaur size is likely of the same order of magnitude of the short-period comets.

International audience; Context: Rosetta is the cornerstone mission of ESA devoted to the study of minor bodies of the Solar System. During its journey to the comet 67P Churyumov-Gerasimenko, the main target, Rosetta also investigates two main belt asteroids, 2867 Steins (fly-by in September 2008) and 21 Lutetia (fly-by in July 2010). Aims: In Spring 2008, we performed a broad observational campaign in order to complete the ground-based photometric and spectroscopic investigation of Steins. Before the Rosetta fly-by, this was the last opportunity to perform ground-based observations useful for calibrating properly the imaging and spectroscopic data obtained by the instruments on board the Rosetta spacecraft. Methods: Visible photometry was carried out at a wide range of phase angles, and visible spectra were acquired at different rotational phases to retrieve information about the absolute magnitude and surface properties. Results: The lightcurve was completely sampled in V and R bands. A rotational period of 6.057±0.003 h and color index V-R=0.51±0.03 mag were computed. We investigate Steins' phase relation over the range between 3.3 and 42 degrees in solar phase angle. The opposition effect is not evident down to the phase angle of 3 degrees, as is typical of other E-type asteroids. Assuming for Steins an opposition surge similar to that of other E-type asteroids, we calculated an absolute magnitude H_R=12.81±0.03, and slope parameter G_R=0.42±0.02. Eight visible spectra, obtained at different rotational phases, exhibit similar behavior, confirming a homogeneous composition of the asteroid surface and the E[II] classification. All spectra display a spectral feature centered on about 0.49 mum that is typical of E-type asteroids and usually attributed to the presence of sulfides (e.g. oldhamite). A tentative model of the surface composition is presented.

Context: The dwarf planet (1) Ceres - next target of the NASA Dawn mission - is the largest body in the asteroid main belt; although several observations of this body have been performed so far, the presence of surface water ice is still questioned. Aims: Our goal is to better understand the surface composition of Ceres, and to constrain the presence of exposed water ice. Methods: We acquired new visible and near-infrared spectra at the Telescopio Nazionale Galileo (TNG, La Palma, Spain), and reanalyzed literature spectra in the 3-$\mu$m region. Results: We obtained the first rotationally-resolved spectroscopic observations of Ceres at visible wavelengths. Visible spectra taken one month apart at almost the same planetocentric coordinates show a significant slope variation (up to 3 %/10$^3\AA$). A faint absorption centered at 0.67 $\mu$m, possibly due to aqueous alteration, is detected in a subset of our spectra. The various explanations in the literature for the 3.06-$\mu$m feature can be interpreted as due to a variable amount of surface water ice at different epochs. Conclusions: The remarkable short-term temporal variability of the visible spectral slope, and the changing shape of the 3.06-$\mu$m band, can be hints of different amounts of water ice exposed on the surface of Ceres. This would be in agreement with the recent detection by the Herschel Space Observatory of localized and transient sources of water vapour over this dwarf planet., Comment: Accepted for publication in A&A; last version before language editing

Asteroid (410777) 2009 FD could hit Earth between 2185 and 2196. The long term propagation to the possible impacts and the intervening planetary encounters make 2009 FD one of the most challenging asteroids in terms of hazard assessment. To compute accurate impact probabilities we model the Yarkovsky effect by using the available physical characterization of 2009 FD and general properties of the near Earth asteroid population. We perform the hazard assessment with two independent methods: the first method is a generalization of the standard impact monitoring algorithms in use by NEODyS and Sentry, while the second one is based on a Monte Carlo approach. Both methods generate orbital samples in a seven-dimensional space that includes orbital elements and the parameter characterizing the Yarkovsky effect. The highest impact probability is 2.7 x 10(-3) for an impact during the 2185 Earth encounter. Impacts after 2185 corresponding to resonant returns are possible, the most relevant being in 2190 with a probability of 3 x 10(-4). Both numerical methods can be used in the future to handle similar cases. The structure of resonant returns and the list of the possible keyholes on the target plane of the scattering encounter in 2185 can be predicted by an analytic theory.

Aims: In the framework of a large program, we observed (55638) 2002 VE95 with the ESO-VLT telescope to better constrain its surface composition and to investigate the possible heterogeneity of the surface. Methods: We report new near-infrared observations performed in 2007 and 2008. Using the new constraints of the albedo obtained by Herschel Space Observatory observations, a surface model was computed using the complete set of spectra (from visible to the near-infrared) as well as those of the previous published data to investigate the surface composition properties of (55638) 2002 VE95. Results: The surface is heterogeneous. This red object is covered by different icy compounds, such as water (4-19%) and methanol (10-12%). Different organic compounds, such as titan and triton tholins seem also to be present in the surface. The amount of the components is different depending on the observed area. That methanol ice seems to be present mainly on very red surface favors the hypothesis that surfaces of very red objects are more primordial. Based on observations made with ESO Very Large Telescope at the La Silla-Paranal Observatory under program ID 178.C-0036 (PI: A. Barucci) and the Herschel Space Observatory. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

X-Shooter is the first second-generation instrument for the ESO-VLT. It as a spectrograph covering the 300 - 2480 nm spectral range at once with a high resolving power. These properties enticed us to observe (136199) Eris during the science verification of the instrument. The target has numerous absorption features in the optical and near-infrared domain which has been observed by different authors, showing differences in their positions and strengths. We attempt at constraining the existence of super-volatiles, e.g., CH4, CO and N2, and in particular try to understand the physical-chemical state of the ices on Eris' surface. We observed Eris in the 300-2480 nm range and compared the newly obtained spectra with those available in the literature. We identified several absorption features, measuring their positions and depth and compare them with those of reflectance of pure methane ice obtained from the optical constants of this ice at 30 K to study shifts in their positions and find a possible explanation for their origin. We identify several absorption bands in the spectrum all consistent with the presence of CH4 ice. We do not identify bands related with N2 or CO. We measured the central wavelengths of the bands and find variable shifts, with respect to the spectrum of pure CH4 at 30 K. Conclusions. Based on these wavelength shifts we confirm the presence of a dilution of CH4 in other ice on the surface of Eris and the presence of pure CH4 spatially segregated. The comparison of the centers and shapes of these bands with previous works suggest that the surface is heterogeneous. The absence of the 2160 nm band of N2 can be explained if the surface temperature is below 35.6 K, the transition temperature between the alpha and beta phases of this ice. Our results, including the reanalysis of data published elsewhere, point to an heterogeneous surface on Eris., 15 pages, 5 figures

A Large Program (LP) has been carried out at ESO–VLT using almost simultaneously the UT1, UT2 and UT4 telescopes (Cerro Paranal, Chile). The aim of this Large Program was to obtain simultaneous visible and near-IR spectroscopic measurements (using FORS, ISAAC and SINFONI instruments) with a S/N ratio as high as possible for almost all objects among different dynamical groups observable within the VLT capability. In this paper we present results on the second half of the Large Program which includes new near-infrared spectroscopy data of 20 objects. For 12 of them for which we had obtained the complete spectral range (V + J + H + K bands), we apply a radiative transfer model to the entire spectral range to constrain their surface composition. We also present an analysis of all near-IR spectral data available on TNOs and Centaurs from both the complete LP and the literature. An overview for a total sample of 75 objects is thus carried out analyzing the ice content with respect to the physical and dynamical characteristics. The major new results are: (i) all objects classified as BB class seem to have icy surfaces; (ii) the possible presence of CH 3 OH has primarily been detected on very red surfaces (RR class objects) and (iii) the majority of Centaurs observed multiple times have an heterogeneous composition.

The study of the surface properties of Centaurs and Trans-Neptunian Objects (TNOs) provides essential information about the early conditions and evolution of the outer Solar System. Due to the faintness of most of these distant and icy bodies, photometry currently constitutes the best technique to survey a statistically significant number of them. Our aim is to investigate color properties of a large sample of minor bodies of the outer Solar System, and set their taxonomic classification. We carried out visible and near-infrared photometry of Centaurs and TNOs, making use, respectively, of the FORS2 and ISAAC instruments at the Very Large Telescope (European Southern Observatory). Using G-mode analysis, we derived taxonomic classifications according to the Barucci et al. (2005a) system. We report photometric observations of 31 objects, 10 of them have their colors reported for the first time ever. 28 Centaurs and TNOs have been assigned to a taxon. We combined the entire sample of 38 objects taxonomically classified in the framework of our programme (28 objects from this work; 10 objects from DeMeo et al. 2009a) with previously classified TNOs and Centaurs, looking for correlations between taxonomy and dynamics. We compared our photometric results to literature data, finding hints of heterogeneity for the surfaces of 4 objects., Comment: 7 pages, 4 figures. To be published in Astronomy and Astrophysics

International audience; Context: The knowledge of the rotational periods of the small bodies in the outer Solar System is a useful tool for retrieving information on the internal structure of the observed objects and for having hints on the collisional evolution state of the whole population. Aims: In order to investigate the physical nature of Centaurs and TNOs, we analysed the rotational properties of a selected sample. Methods: Photometric observations of 2 Centaurs (12929 1999 TZ1 and 95626 2002 GZ{32}), and 5 Trans-Neptunian Objects (42355 Typhon, 47932 2000 GN{171}, 65489 Ceto, 90568 2004 GV9, and 120132 2003 FY{128}) were carried out with the New Technology Telescope (NTT) at the European Southern Observatory La Silla (Chile) in the framework of the ESO Large Programme 178.C-0036 (PI. M.A. Barucci). Results: These observations allow us to estimate the rotational rate of three objects, to confirm previously published periods of two bodies, and to have the first single night lightcurves of 42355 Typhon and 120132 2003 FY{128}. Conclusions: These data allow us to improve the available sample of determined rotational periods of TNOs and Centaurs. For 5 out of the 7 observed objects we have estimated the axis ratio a/b, hence the density. Our new results seem to confirm the density/dimension trend, found by Sheppard et al. (2008, in The Solar System Beyond Neptune (Univ. Arizona press), 129), with larger (brighter) objects having higher densities.

The Campo Imperatore Near Earth Object Survey (CINEOS) is an Italian survey dedicated to the search and follow-up of Near Earth Objects (NEOs). It is operated with the 90 cm f/3 Schmidt telescope at the Campo Imperatore of the Rome Astronomical Observatory (INAF-OAR) as a joint project with the Istituto di Astrofisica Spaziale and Fisica Cosmica (INAF-IASF) in Rome. Since the end of 2001 CINEOS has covered about 4,250 sq. deg to 20th magnitude in the course of about 160 nights. This effort led to the discovery of 7 Near Earth Asteroids (NEAs), 1 comet (167P/CINEOS; a member of the Centaur group) and a few other unusual objects including 2004 XH50 with a unique comet-like orbit. CINEOS has also contributed almost 2,200 preliminary designations and over 30,000 detections to the Minor Planet Center. About 20% of the survey effort was carried out at low solar elongations (LSE), although no object with an orbit interior (Inner Earth Objects, IEO class) or nearly interior to the Earth (Aten class) was found. The work at LSE was, however, very important to test survey strategies implemented with larger telescopes. We also provide the results of a CINEOS simulation on a reliable NEO population model based on the results of two larger scale surveys, Spacewatch and LINEAR.

Although close to the Sun, Mercury has a unique surface, poorer in iron than the surface of the Moon, but surprisingly rich in volatile elements. These essential discoveries of the MESSENGER mission have raised questions that the BepiColombo mission (ESA/JAXA) will try to answer, thanks in particular to the SIMBIO-SYS instrument, which will provide spectral images of the Mercury surface with a spatial resolution 10 to 100 times higher than that achieved by MESSENGER. Among these fundamental questions is the accurate chemical and mineralogical composition of Mercury. My thesis adresses the problem through a multidisciplinary approach. A first angle consists in using the data provided by MESSENGER to map in color the Shakespeare quadrangle. My work has made it possible to define 1) spectral units of the quadrangle associated with very precise values of various spectral parameters, and 2) regions of interest to be analyzed and characterized notably by the VIHI hyperspectral imager (0.4-2.0 μm), one of the channels of SIMBIO-SYS. The second angle consists of laboratory experiments : heating, cooling and irradiation of possible mineralogical analogues of Mercury’s surface. The aim is to anticipate the arrival of BepiColombo and to know the effects of these alterations on the spectral properties of the minerals. Results obtained from spectroscopic measurements of hermean mineral analogues subjected to Mercury surface conditions have revealed clear variations in their spectral properties (e.g. position and shape of absorption bands).; Bien que proche du Soleil, Mercure possède une surface unique, plus pauvre en fer que la surface de la Lune, mais étonnament riche en éléments volatils. Ces découvertes essentielles de la mission MESSENGER ont soulevé des questions auxquelles tentera de répondre la mission BepiColombo (ESA/JAXA) grâce notamment à l’instrument SIMBIO-SYS qui fournira des images spectrales de la surface de Mercure avec une résolution spatiale 10 à 100 fois plus élevée que celle atteinte par MESSENGER. Parmi ces questions fondamentales figure la composition chimique et minéralogique précise de Mercure. Ma thèse aborde la problématique par une approche pluridisciplinaire. Un premier angle consiste en l’exploitation des données fournies par MESSENGER en cartographiant en couleurs le quadrangle Shakespeare. Mes travaux ont notamment permis de définir 1) des unités spectrales du quadrangle associées à des valeurs bien précises de divers paramètres spectraux, et 2) des régions d’intérêt à analyser et caractériser notamment par le spectro-imageur VIHI (0,4-2,0 μm), une des voies de SIMBIO-SYS. Le deuxième angle consiste en des expériences de laboratoire : chauffage, refroidissement et irradiation d’analogues minéralogiques possibles de la surface de Mercure. Le but est d’anticiper l’arrivée de BepiColombo et de savoir quels sont les effets de ces altérations sur les propriétés spectrales de ces minéraux. Les résultats obtenus de mesures spectroscopiques d’analogues de minéraux herméens soumis aux conditions de la surface de Mercure ont permis de mettre en évidence des variations claires de leurs propriétés spectrales (e.g. position et forme de bandes d’absorption).