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In this work we present the main characteristics that derive from the analysis of the luminous part of the trajectory of a meteoroid. Our study is based on applying the α-β algorithm (Gritsevich 2008, Gritsevich 2009, Gritsevich et al. 2012, Lyytinen and Gritsevich 2016, Sansom et al. 2019, Boaca et al. 2022) to the latest detections recorded by the MOROI (Nedelcu et al. 2018) component of the FRIPON network (Colas et al. 2020). Our input parameter are the height and velocity of the meteoroid and the way they change with time. Based on this we determine the ballistic coefficient α and the mass loss parameter β for each analysed meteor event. The α-β algorithm is used in order to decide which of the fireball events produce meteorites and which are fully ablating in the atmosphere. Furthermore, the α and β parameters allow us to determine the mass of the studied meteoroids e.g. at the beginning and at the end of the luminous trajectory.Boaca I., et al. (2022), ApJ, 936, 150.Colas, F., et al. (2020), A&A, 644, A53.Gritsevich, M. I. (2008), DokPh, 53, 97.Gritsevich, M. I. (2009), AdSpR, 44, 323.Gritsevich, M. I., et al., (2012), CosRe, 50, 56.Lyytinen, E., & Gritsevich, M. (2016), P&SS, 120, 35.Nedelcu, D. A., et al. (2018), RoAJ, 28, 57.Sansom, E. K., et al. (2019), ApJ, 885, 115.Acknowledgement.The work of IB and AN was partially supported by a grant of the Ministry of National Education and Scientific Research, PNIII-P2-1214/25.10.2021, program no. 36SOL/2021. MG acknowledges the Academy of Finland project no. 325806 (PlanetS).

We report 491 new near-infrared spectroscopic measurements of 420 Near-Earth Objects (NEOs) collected on NASA’s IRTF in the context of MITHNEOS (PI: DeMeo). The measurements were combined with previously published data (Binzel et al. 2019) and bias-corrected for albedo variations to derive the intrinsic compositional distribution of the overall NEO population. We also investigated individual subpopulations coming from various escape routes (ERs) in the asteroid belt by use of the dynamical model of Granvik et al. (2018). The resulting distributions reflect well the compositional gradient of the asteroid belt, with decreasing fractions of silicate-rich (S- and Q-type) bodies and increasing fractions of carbonaceous (B-, C-, D- and P-type) bodies as a function of increasing ER distance from the Sun. The compositional match between NEOs and their predicted source populations validates dynamical models used to identify ERs and argues against strong composition change in the main belt between approximately 5 km and 100 m. An exception comes from the overabundance of D-type NEOs from the 5:2J and, to a lesser extent, the 3:1J and ν6 ERs, hinting at the presence of a large population of small D-type asteroids in the main belt. Alternatively, this excess may indicate spectral evolution from D-type surfaces to C and P types due to space weathering or point to preferential fragmentation of D-types in the NEO space. No further evidence for the existence of collisional families in the main belt, below the detection limit of current main-belt surveys, was found in this work.

Anghel, S., et al., The increase in detector sensitivity and availability in the past three decades has allowed us to derive knowledge of the meteoroid flux and impact energy into the Earth's atmosphere. We present the multi-instrument detected 2018 December 22 fireball over Western Pyrenees, and compare several techniques aiming to obtain a reliable method to be used when measuring impacts of similar scale. From trajectory data alone, we found a bulk density of 3.5 g cm-3 to be the most likely value for the Pyrenean meteoroid. This allowed to further constrain the dynamic mass, which translated into a kinetic energy of 1 ton TNT (4.184 × 109 J). For the second energy derivation, via the fireball's corrected optical radiation, we obtained a more accurate empirical relation measuring well-studied bolides. The result approximates to 1.1 ton TNT, which is notably close to the nominal dynamic result, and agrees with the lower margin of the seismic-based energy estimation, yet way lower than the infrasound estimate. Based on the relation derived in this study, we consider the nominal estimate from both the dynamic and photometric methods to be the most accurate value of deposited energy (1 ton TNT). We show that the combination of these two methods can be used to infer the meteoroid density. Among the methods presented in this paper, we found that the optical energy is the most reliable predictor of impact energy near the ton TNT-scale., S. Anghel and D. A. Nedelcu were supported by a grant of the Romanian Ministry of Research and Innovation, CCCDI - UEFISCDI, project number PN-III-P1-1.2-PCCDI-2017-0226/16PCCDI/2018, within PNCDI III. EP-A and JMT-R acknowledge funding from PGC2018-097374-B-I00 (MCI-AEI-FEDER, EU). M. Birlan work was partly supported by SEEING-IEA CNRS program. R. Hueso and A. Sánchez-Lavega were supported by Diputación Foral de Bizkaia and Gobierto Vasco IT1366-19.

Context (121) Hermione is a large binary asteroid [1] located at the outer edge of the asteroid belt in the Cybele region, where asteroids are thought to be linked to the outer Solar System. Hermione has a Ch/Cgh-type that has been linked to CM chondrites. Adaptive optics observations between 2003 and 2008 suggest a rare bilobate shape for the primary [2,3]. However, Hermione’s shape and bulk density (ranging between 1.4 and 2 g.cm-3) remain poorly constrained to this day. Aim We acquired spatially resolved images and optical lightcurves of Hermione during its close apparition of September 2021. It was the best chance in 13 years to acquire such high angular resolution images (angular diameter = 0.14”). We aimed to constrain Hermione’s 3D shape, hence its volume, and the orbit of its satellite, hence the mass of the system. Combining the volume and the mass allows to constrain the bulk density with high accuracy. Methods We obtained 8 series of 5 images with the SPHERE/ZIMPOL instrument on the Very Large Telescope (ESO Program ID 107.22UT.001; PI: P. Vernazza). These images were combined with optical lightcurves and stellar occultations by the ADAM and MPCD methods [4,5] to reconstruct the asteroid’s 3D shape. For the determination of the satellite’s orbit, we complemented the SPHERE images with a compilation of archival data from other large ground-based AO instruments (KeckII/NIRC2, ESO/VLT/NACO and Gemini-North/NIRI). Then, we used the meta-heuristic algorithm Genoid [6] to accurately determine the orbital elements. Results The determined volume and mass of Hermione yield a new higher bulk density of ~1.7 g.cm-3, more compatible with its Ch/Cgh classification. We will also present our analyse of the shape and compare it with other elongated Ch/Cgh asteroids. Bibliography [1] Merline et al. (2002), IAU Circ. 7980 [2] Marchis et al. (2005), Icarus, 178, 2, p. 450-464 [3] Descamps et al. (2009), Icarus, 203, 1, p. 88-101 [4] Viikinkoski, M., Kaasalainen, M., & Durech, J. (2015), A&A, 576, A8 [5] Capanna, C., Gesquière, G., Jorda, L., Lamy, P., & Vibert, D. (2013), The Visual Computer, 29, 825 [6] Vachier, F., Berthier, J. and Marchis, F. (2012), A&1, 543, A68

Context – Cybele asteroids constitute an appealing reservoir of primitive material genetically linked to the outer Solar system. The physical properties (size, shape) of the largest members can be directly measured with high-angular resolution imagers mounted on large (8-m class) telescopes. Aim – We took advantage of the bright apparition of the most iconic member of the Cybele population, (65) Cybele, in July and August 2021 to acquire high angular resolution images and optical light curves of the asteroid that were used to analyze its shape, topography and bulk properties (volume, density). Methods – Eight series of images were acquired with SPHERE+ZIMPOL on the Very Large Telescope (ESO Program ID 107.22QN.001; PI: Marsset) and combined with optical light curves to reconstruct the shape of the asteroid using the ADAM (Viikinkoski et al. 2015), MPCD (Capanna et al. 2013) and SAGE (Bartczak & Dudziński 2018) algorithms. Results – We will present Cybele’s bulk properties, including its volume-equivalent diameter and average density, in the context of other low-albedo P-type asteroids. We will show that Cybele’s shape and rotation state are entirely compatible to those of a Maclaurin equilibrium figure, opening up the possibility that D≥260 km (M≥1.4x10^19 kg) small bodies from the outer Solar System formed at equilibrium. We will further present the results of N-body simulations used to explore whether the equilibrium shape of Cybele is the result of a large resetting impact (similarly to the case of Hygiea; Vernazza et al. 2020), or if it is primordial (i.e., the result of early internal heating due to the radioactive decay of short- and long-lived radionuclides).

1. IntroductionThe Fireball Recovery and Inter Planetary Observation Network (FRIPON) network [1] uses all-sky cameras in order to detect fireballs. The FRIPON network comprises over 150 cameras installed all over Europe [1]. In this work we focus on the results obtained by the Meteorite Orbits Reconstruction by Optical Imaging (MOROI) [2] component of the FRIPON network in Romania. As of May 2022, the MOROI network detects the events with the use of 13 all-sky cameras.2. MethodsThe method for computing the fireball trajectory used by FRIPON is presented in [3].The height, velocity and slope γ of the meteoroid are the input data for computing the ballistic coefficient α and the mass-loss parameter β. We select the candidates that are likely to produce meteorites of the ground using the α-β algorithm presented in [4], [5], [6], [7]. 3. Results Starting from January 2021 (the starting moment of data fusion of the MOROI network into the FRIPON network) until the present time (May 2022) over 100 meteors were detected. We present the most spectacular events that are likely to result on a meteorite production on the surface of the Earth. Figure 1: The outcome of the FRIPON (MOROI) detections in Romania In Figure 1 are represented the coordinates of the meteoroids with noticeable deceleration in the (ln(αsinγ),lnβ) coordinates system. The values of the shape parameter correspond to the cases when the meteoroid doesn’t rotate (µ=0) or rotates uniformly (µ=2/3). The boundaries (‘likely fall’, ‘possible fall’, ‘unlikely fall’) are represented for meteoroids with final mass of 50 g. We processed the 100 detections of the FRIPON (MOROI) network in Romania. From this amount of data, we found 15 fireball events with noticeable deceleration. We found one event in the ‘likely fall’ area and three events in the ‘possible fall’ area. The fireball that is likely to produce meteorites was detected by the MOROI network on 24.11.2021 at 19:20:57 UT. We model the dark flight trajectory of the meteoroids with the ‘likely fall’ and ‘possible fall’ outcomes and determine their strewn field with the model presented in [8], [9]. We use the wind model from the European Centre for Medium-Range Weather Forecasts (ECMWF). A meteorite recovery campaign will be organised to identify the strewn field area. Acknowledgement. The work of IB and MB was partially supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P1-1.1-PD-2019-0784, within PNCDI III. The work of IB, MB, AN was partially supported by a grant of the Ministry of National Education and Scientific Research, PNIII-P2-1214/25.10.2021, program no. 36SOL/2021. JM and MG acknowledge the Academy of Finland project no. 325806 (PlanetS). References: [1] Colas F., Zanda B., Bouley S., Jeanne S., Malgoyre A., Birlan M., Blanpain C., Gattacceca J., Jorda L., Lecubin J., et al. (385 more) FRIPON: a worldwide network to track incoming meteoroids. Astronomy &. Astrophys. 644, A53. doi:10.1051/0004-6361/202038649. 2020. [2] Nedelcu D.A., Birlan M., Turcu V., Boaca I., Badescu O., Gornea A., Sonka A.B., Blagoi O., Danescu C., Paraschiv P. Meteorites Orbits Reconstruction by Optical Imaging (MOROI) Network. Romanian Astronomical Journal 28(1), 57 – 65. 2018. [3] Jeanne, S., Colas, F., Zanda, B., Birlan, M., Vaubaillon, J., Bouley, S., Vernazza, P., Jorda, L., Gattacceca, J., Rault, J. L., Carbognani, A., Gardiol, D., Lamy, H., Baratoux, D., Blanpain, C., Malgoyre, A., Lecubin, J., Marmo, C., Hewins, P. Calibration of fish-eye lens and error estimation on fireball trajectories: application to the FRIPON network. Astronomy and Astrophysics, 627:A78. 2019. [4] Gritsevich, M. I. The Pribram, Lost City, Innisfree, and Neuschwanstein falls: An analysis of the atmospheric trajectories. Solar System Research.42, 372–390. 2008. [5] Gritsevich, M.I., Stulov, V.P., Turchak, L.I. Consequences of collisions of natural cosmic bodies with the Earth's atmosphere and surface. Cosmic Research vol.50, no.1, 56-64. 2012. [6] Sansom, E.K., Gritsevich, M., Devillepoix, H.A.R., Jansen-Sturgeon, T., Shober, P., Bland, P.A., Towner, M.C., Cupák, M., Howie, R.M., Hartig, B.A.D. Determining Fireball Fates Using the α-β Criterion. Astrophysical Journal 885(2):115. 2019. [7] Boaca I., Gritsevich M., Birlan M., Nedelcu, A., Boaca, T., Colas, F., Malgoyre, A., Zanda, B., Vernazza P., to be submitted. 2022. [8] Moilanen, J., Gritsevich, M., Lyytinen, E., Determination of strewn fields for meteorite falls, Monthly Notices of the Royal Astronomical Society 503, 3337–3350. 2021. [9] Boaca I., Nedelcu A., Birlan M., Boaca T., Anghel S. Mathematical model for the dark-flight trajectory of a meteoroid, Romanian Astronomical Journal, Vol. 31, No. 2. 2021.

Context – The Bepi-Colombo mission (ESA-JAXA) will reach Mercury in December 2025 (Benkhoff et al. 2021). Onboard, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS; Hiesinger et al. 2010) will study the surface composition and map the surface temperature. The interpretation of the MERTIS data requires a dedicated thermal model, able to predict accurately the surface temperature at any location and any time on Mercury. Previous works on this topic have been performed by, e.g., Wohlfarth et al. (2021, 2022). The scientific objectives are to produce thermal inertia maps, to look for thermal anomalies (cold or hot spots), to look at the icy environment (polar cups craters), and to determine the thermal continuum for compositional studies.Thermal model – We developed a thermal model that considers solar heating, thermal emission, heat conductivity, projected shadows, and self-heating (i.e. mutual heating of facets seeing each other’s). This thermal model is inherited and adapted from our previous works on small bodies (e.g. Groussin et al. 2004). Our thermal model is applied to the USGS Digital Elevation Model of Mercury with 20 million facets, and run for six revolutions of Mercury, i.e. three complete thermal cycles, until convergence. The geometry is computed by the OASIS software (Jorda et al. 2016). The thermal model is parallelized, and for a given set of parameters (typically for a given thermal inertia), it runs in two hours for a polar cup (1.4 million facets) on a 24 cores CPU PC. The output of the model is the surface temperature map, for any position (time) of Mercury on its orbit, and for various thermal inertia. The surface temperature can then be used to compute the spectral energy distribution, to be compared with the MERTIS data.Preliminary results – We applied our thermal model to the Northern polar cup of Mercury. Figure 1 shows the maximum surface temperature over one complete thermal cycle, i.e. two revolutions of Mercury, for a thermal inertia of 50 J/K/m2/m1/2. The maximum temperature varies strongly across the surface, and many surface morphologies like craters are still visible in the thermal infrared, with the side facing the pole being colder than the side facing the equator. Many blue patches are also visible, inside craters, and correspond to areas of permanent shadows, where the temperature is constantly below 150 K, allowing the presence of exposed water ice. Those results are similar to those obtained by Paige et al. (2013), also discussed by Chabot et al. (2019).Perspectives – The current shape model, with 20 million facets, provides a spatial resolution of 3.7 km2 per facet on average, while the MERTIS instrument will have a spatial resolution up to 0.1 km2 per pixel (at 400 km altitude). Even though the topography is crucial for thermal models, unresolved surface roughness further influences the thermal behavior, but occurs on much smaller scales of approximately 0.5 – 1 cm (Bandfield et al. 2015). The current standard is therefore to include a model that addresses surface roughness to mitigate directional effects, which are due to shadowing and self-heating. We will do this by adding fractal roughness, as we already did in the past for small bodies in particular (Davidsson et al. 2015), as illustrated in Figure 2.ReferencesBandfield et al. 2015, Icarus 248, 357Benkhoff et al. 2021, Space Science Review 217, 90Chabot et al. 2019, Mercury – The view after MESSENGER, Cambridge Univ. Press, 13Davidsson et al. 2015, Icarus 252, 1Groussin et al. 2004, Astronomy & Astrophysics 419, 375Hiesinger et al. 2010, Planetary and Space Science 58, 144Jorda et al. 2016, Icarus 277, 257Paige et al. 2013, Science 339, 300Wohlfarth et al. 2021, LPSC conference 52, 2548Wohlfarth et al. 2022, LPSC conference 53, 2431Figure 1 – Maximum surface temperature on the Northern polar cup of Mercury, for a thermal inertia of 50 J/K/m2/m1/2. The blue areas are in permanent shadows, inside craters, with a temperature constantly below 150 K, allowing the presence of exposed water ice. Figure 2 – Example of a terrain with 32000 facets, on which we added fractal roughness, with a fractal dimension of 2.2.

The Mars Moon eXploration (MMX) mission by the Japan Aerospace Exploration Agency, JAXA, which is going to explore the Martian Moons Phobos and Deimos and also return samples from Phobos back to Earth will also deliver a small (about 25 kg) Rover to the surface of Phobos.The payload of this rover consists of a Raman spectrometer (RAX) to measure the mineralogical composition of the surface material, a stereo pair of cameras looking affront (NavCam, also used for navigation) to provide the properties of the investigated area, a radiometer (miniRAD) to measure the surface brightness temperature and determine thermal properties of both regolith and rocks, and two cameras looking at the wheel-surface interface (WheelCam) to investigate the properties and dynamics of the regolith. The cameras will, thus, serve for both, technological and scientific needs.After the Rover has been delivered by the main spacecraft, it shall upright itself and operate for about 100 days on the surface of Phobos to investigate terrain and mineralogy along its path.The measurements are going to provide ground truth by studying in-situ properties such as the physical properties and heterogeneity of the surface material.MMX is planned to be launched in September 2024, the Rover delivery is currently planned for 2027.The Rover is a contribution by the Centre National d’Etudes Spatiales (CNES) and the German Aerospace Center (DLR) with additional contributions from INTA (Spain) and JAXA.

Some of the fields of research that have captured the persistent interest of both scientists and the general public are meteor phenomena. The main goal in the study of meteoroid impacts into Earth’s atmosphere is the recovery of the remnant matter after the ablation in the form of meteorites. This is a complementary approach, yet cheap alternative, to a sample return mission. Meteoroids are messengers since the time of the formation of the solar system due to the fact that they have preserved the same composition. The study of meteorites provides information regarding the chemical composition from which the planets formed. The increasing number of all-sky camera networks in recent years has resulted in a large set of events available for study. Thus, it is very important to use a method that determines whether the meteoroid could produce a meteorite or not. In this paper we study the meteors detected by the FRIPON network in Romania with the use of all-sky cameras. We focus on the events with noticeable deceleration (V f /V 0 < 0.8). We determine the ballistic coefficient α and the mass-loss parameter β for the selected sample. Based on this analysis the events are classified in three categories: (1) meteoroids that are likely to produce meteorites; (2) meteoroids that can possibly produce meteorites; (3) meteoroids that are unlikely to produce meteorites. The entry and final mass are determined for each event. From the recorded fireballs, we identified one possible meteorite dropper, and we analyzed its dynamical evolution.

We identify spectral similarities between asteroids and meteorites. We identify spectral matches between 500 asteroid spectra and over 1,000 samples of RELAB meteorite spectra over 0.45-2.5 microns. We reproduce many major and previously known meteorite-asteroid connections and find possible new, more rare or less-established connections. Well-established connections include: ordinary chondrites (OC) with S-complex asteroids; pristine CM carbonaceous chondrites with Ch-type asteroids and heated CMs with C-type asteroids; HED meteorites with V-types; enstatite chondrites with Xc-type asteroids; CV meteorites with K-type asteroids; Brachinites, Pallasites and R chondrites with olivine-dominated A-type asteroids. We find a trend from Q, Sq, S, Sr to Sv correlates with LL to H, with Q-types matching predominately to L and LL ordinary chondrites, and Sr and Sv matching predominantly with L and H ordinary chondrites. Ordinary chondrite samples that match to the X-complex, all measurements of slabs and many labeled as dark or black (shocked) OCs. We find carbonaceous chondrite samples having spectral slopes large enough to match D-type asteroid spectra. In many cases the asteroid type to meteorite type links are not unique. While there are well established matches between an asteroid class and meteorite class, there are less common but still spectrally compatible matches between many asteroid types and meteorite types. This result emphasizes the diversity of asteroid and meteorite compositions and highlights the degeneracy of classification by spectral features alone. Recent and upcoming spacecraft missions will shed light on the compositions of many of the asteroid classes, particularly those without diagnostic features, (C-, B-, X-, and D-types), with measurements of Ceres, Ryugu, Bennu, Psyche, and C-, P-, and D-types as part of the Lucy mission., Comment: Accepted for publication in Icarus. 38 pages, 8 figures

Dust emission was detected on main-belt asteroid 596 Scheila in December 2010, and attributed to the collision of a few-tens-of-meters projectile on the surface of the asteroid. In such impact, the ejected material from the collided body is expected to mainly comes from its fresh, unweathered subsurface. Therefore, it is expected that the surface of 596 was partially or entirely refreshed during the 2010 impact. By combining spectra of 596 from the literature and our own observations, we show that the 2010 impact event resulted in a significant slope change in the near-infrared (0.8 to 2.5 {\mu}m) spectrum of the asteroid, from moderately red (T-type) before the impact to red (D-type) after the impact. This provides evidence that red carbonaceous asteroids become less red with time due to space weathering, in agreement with predictions derived from laboratory experiments on the primitive Tagish Lake meteorite, which is spectrally similar to 596. This discovery provides the very first telescopic confirmation of the expected weathering trend of asteroids spectrally analog to Tagish Lake and/or anhydrous chondritic porous interplanetary dust particles. Our results also suggest that the population of implanted objects from the outer solar system is much larger than previously estimated in the main-belt, but many of these objects are hidden below their space-weathered surface., Comment: 11 pages, 5 figures, 1 tables, Accepted for publication in ApJ Letters

The orbit of the outer satellite Alexhelios of (216) Kleopatra is already constrained by adaptive-optics astrometry, obtained with the VLT/SPHERE instrument. However, there is also a preceding occultation event in 1980 attributed to this satellite. Hereinafter, we try to link all observations, spanning 1980--2018. We find the nominal orbit exhibits an unexplained shift by $+60^\circ$ in the true longitude. Using both periodogram analysis and an $\ell = 10$ multipole model suitable for the motion of mutually interacting moons about the irregular body, we confirmed that it is not possible to adjust the respective osculating period $P_2$. Instead, we were forced to use a model with tidal dissipation (and increasing orbital periods) to explain the shift. We also analyzed light curves, spanning 1977--2021, and searched for the expected spin deceleration of Kleopatra. According to our best-fit model, the observed period rate is $\dot P_2 = (1.8\pm 0.1)\cdot 10^{-8}\,{\rm d}\,{\rm d}^{-1}$ and the corresponding time lag $\Delta t_2 = 42\,{\rm s}$ of tides, for the assumed value of the Love number $k_2 = 0.3$. It is the first detection of tidal evolution for moons orbiting 100-km asteroids. The corresponding dissipation factor $Q$ is comparable with other terrestrial bodies, albeit at a higher loading frequency $2|\omega-n|$. We also predict a secular evolution of the inner moon, $\dot P_1 = 5.0\cdot 10^{-8}$, as well as a spin deceleration of Kleopatra, $\dot P_0 = 1.9\cdot 10^{-12}$. In alternative models, with moons captured in the 3:2 mean-motion resonance or more massive moons, the respective values of $\Delta t_2$ are a factor of 2--3 lower. Future astrometric observations by direct imaging or occultations should allow to distinguish between these models, which is important for the internal structure and mechanical properties of (216) Kleopatra., Comment: accepted in A&A

Vernazza, P., et al., Until recently, the 3D shape, and therefore density (when combining the volume estimate with available mass estimates), and surface topography of the vast majority of the largest (D ≥ 100 km) main-belt asteroids have remained poorly constrained. The improved capabilities of the SPHERE/ZIMPOL instrument have opened new doors into ground-based asteroid exploration. Aims. To constrain the formation and evolution of a representative sample of large asteroids, we conducted a high-angular-resolution imaging survey of 42 large main-belt asteroids with VLT/SPHERE/ZIMPOL. Our asteroid sample comprises 39 bodies with D ≥ 100 km and in particular most D ≥ 200 km main-belt asteroids (20/23). Furthermore, it nicely reflects the compositional diversity present in the main belt as the sampled bodies belong to the following taxonomic classes: A, B, C, Ch/Cgh, E/M/X, K, P/T, S, and V. Methods. The SPHERE/ZIMPOL images were first used to reconstruct the 3D shape of all targets with both the ADAM and MPCD reconstruction methods.We subsequently performed a detailed shape analysis and constrained the density of each target using available mass estimates including our own mass estimates in the case of multiple systems. Results. The analysis of the reconstructed shapes allowed us to identify two families of objects as a function of their diameters, namely spherical and elongated bodies. A difference in rotation period appears to be the main origin of this bimodality. In addition, all but one object (216 Kleopatra) are located along the Maclaurin sequence with large volatile-rich bodies being the closest to the latter. Our results further reveal that the primaries of most multiple systems possess a rotation period of shorter than 6 h and an elongated shape (c=a ≤ 0.65). Densities in our sample range from ∼1.3 g cm-3 (87 Sylvia) to ∼4.3 g cm-3 (22 Kalliope). Furthermore, the density distribution appears to be strongly bimodal with volatile-poor (P ≥ 2.7 g cm-3) and volatile-rich (P ≤ 2.2 g cm-3) bodies. Finally, our survey along with previous observations provides evidence in support of the possibility that some C-complex bodies could be intrinsically related to IDP-like P- and D-type asteroids, representing different layers of a same body (C: core; P/D: outer shell). We therefore propose that P/ D-types and some C-types may have the same origin in the primordial trans-Neptunian disk., We warmly thank the ESO staff at Paranal and in particular Henri Boffin for providing us precious support and advice throughout the entire observing programme. P.V., A.D., M.F., L.J. and B.C. were supported by CNRS/INSU/PNP. The work of T.S-R. was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). TRAPPIST project is funded by the Belgian Fund for Scientic Research (Fond National de la Recherche Scientique, FNRS) under the grant PDR T.0120.21. E.J. is a FNRS Senior Research Associate. F.M. is supported by the National Science Foundation under Grant No. 1743015.

[Aims] To interpret adaptive-optics observations of (216) Kleopatra, we need to describe an evolution of multiple moons orbiting an extremely irregular body and include their mutual interactions. Such orbits are generally non-Keplerian and orbital elements are not constants. [Methods] Consequently, we used a modified N-body integrator, which was significantly extended to include the multipole expansion of the gravitational field up to the order ℓ = 10. Its convergence was verified against the 'brute-force' algorithm. We computed the coefficients Cℓ m, Sℓ m for Kleopatra's shape, assuming a constant bulk density. For Solar System applications, it was also necessary to implement a variable distance and geometry of observations. Our χ2 metric then accounts for the absolute astrometry, the relative astrometry (second moon with respect to the first), angular velocities, and silhouettes, constraining the pole orientation. This allowed us to derive the orbital elements of Kleopatra's two moons. [Results] Using both archival astrometric data and new VLT/SPHERE observations (ESO LP 199.C-0074), we were able to identify the true periods of the moons, P1 = (1.822359 ± 0.004156) d, P2 = (2.745820 ± 0.004820) d. They orbit very close to the 3:2 mean-motion resonance, but their osculating eccentricities are too small compared to other perturbations (multipole, mutual), meaning that regular librations of the critical argument are not present. The resulting mass of Kleopatra, m1 = (1.49 ± 0.16) × 10-12 M· or 2.97 × 1018 kg, is significantly lower than previously thought. An implication explained in the accompanying paper is that (216) Kleopatra is a critically rotating body., Broz, M. et al., This work has been supported by the Czech Science Foundation through grant 21-11058S (M. Brož, D. Vokrouhlický), 20-08218S (J. Hanuš, J. Ďurech), and by the Charles University Research program No. UNCE/SCI/023. This material is partially based upon work supported by the National Science Foundation under Grant No. 1743015. P.V., A.D., M.F. and B.C. were supported by CNRS/INSU/PNP. M.M. was supported by the National Aeronautics and Space Administration under grant No. 80NSSC18K0849 issued through the Planetary Astronomy Program. The work of TSR was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. TRAPPIST is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F. TRAPPIST-North is a project funded by the University of Liège, and performed in collaboration with Cadi Ayyad University of Marrakesh. E. Jehin is a FNRS Senior Research Associate.

Two extremely red main-belt asteroids: 203 Pompeja and 269 Justitia, were identified from combined visible and near-infrared spectroscopic observations collected at the IRTF and SAO observatories. These two asteroids have a redder spectral slope than any other D-type body, which are the reddest objects in the asteroid belt, and similar to RR and IR-class objects found in the outer Solar System among trans-Neptunian objects and Centaurs. Spectroscopic results suggest the presence of complex organic materials on the surface layer of these asteroids, implying that they could have formed in the vicinity of Neptune and been transplanted to the main belt region during a phase of planetary migration. 203 Pompeia is the only very red asteroid known so far among the ~250 bodies with diameter larger than 110 km (i.e. presumably structurally intact) found in the asteroid belt. These discoveries add another piece of evidence that the main asteroid belt hosts a population of bodies that were formed in the outskirt of the Solar System., 12 pages, 5 figures, 1 tables, Accepted for publication in ApJ Letters

Introduction Asteroid (22) Kalliope is the second largest M-type asteroid in the main-belt after (16) Psyche. Kalliope has a bright satellite (D ~ 28km), Linus, discovered in 2001 [Me01, Ma01]. Albeit being a privileged target for adaptive optics (AO) ground-based observations, its density remains elusive with values ranging between 2.4 and 3.7 g cm-3 [Ma03, Dr21]. Here, we present a complete characterization of the topography, bulk density, and internal structure of Kalliope, as well as the dynamic of the system based on high angular resolution imaging observations performed with VLT/SPHERE as part of an ESO large programme (ID: 199.C-0074). Observation We obtained 35 images of Kalliope at 7 epochs near opposition between March and May 2018 and in June 2019 with the VLT/SPHERE/ZIMPOL AO instrument. The first apparition in 2018 covered the south pole of Kalliope while during the second it was close to an equator-on geometry. The north pole was not completely imaged, although 88% of the surface was covered at least once. We compiled 145 lightcurves from databases and we acquired new ones during the 2018 apparition to be used in the 3D shape modelling. For the determination of Linus’s orbit, we complemented the SPHERE images with a compilation of archival data from other large ground-based AO instruments (KeckII/NIRC2, ESO/VLT/NACO and Gemini-North/NIRI). We obtained a total of 82 measurements spanning 42 epochs from 2001 to 2019. Methods We generated shape models of Kalliope with three different shape modelling techniques. We first used the inversion algorithm ADAM [Vi15] and the genetic algorithm SAGE [B18, Du20] that both take lightcurves and AO images as inputs. We then applied our Multi-resolution PhotoClinometry by Deformation (MPCD; [C13, F20]) method on the SPHERE images to reconstruct Kalliope’s 3D shape, starting from both the ADAM and the SAGE models as initial meshes. To study the dynamic of the system, the relative position of Kalliope and Linus were first measured on the images. Then, we used the meta-heuristic algorithm Genoid [Va12] to accurately determine the orbital elements. Results and conclusions The volume of Kalliope from the different modelling techniques and the mass constrained by the precise measurements of its satellite orbit yield a density of ~4.1 g cm-3. This high density is comparable within errors to that of the metallic asteroid (16) Psyche. The best orbital solutions for the satellite are found when the quadrupole J2 tends toward 0. However, Kalliope’s shape implies a non-zero J2 when assuming a homogeneous interior density. This suggests an inhomogeneous, differentiated internal structure. Bibliography [B18] Bartczak, P. and Dudzinski, G. 2018, MNRAS, 473 [C13] Capanna, C., Gesquière, G., Jorda, L., Lamy, P., & Vibert, D. 2013, The Visual Computer, 29, 825 [Dr21] Drummond, J. D., Merline, W. J., Carry, B., et al. 2021, Icarus, 358 [Du20] Dudzinski, G., Podlewska-Gaca, E., Bartczak, P., et al. 2020, MNRAS, 499 [F20] Ferrais, M., Vernazza, P., Jorda, L., et al. 2020, A&A, 638, L15 [Ma01] Margot, J. L. and Brown, M. E. 2001, IAU Circ., 7703, 3 [Ma03] Margot, J. L. and Brown, M. E. 2003, Science, 300, 1939 [Me01] Merline, W. J., Menard, F., Close, L., et al. 2001, IAU Circ., 7703, 2 [Va12] Vachier, F., Berthier, J. and Marchis, F. 2012, A&1, 543, A68 [Vi15] Viikinkoski, M., Kaasalainen, M., & Durech, J. 2015, A&A, 576, A8

Drolshagen, E., et al., [Context] In meteor physics, the luminous efficiency τ is used to convert the meteor's magnitude to the corresponding meteoroid's mass. However, a lack of sufficiently accurate verification methods or adequate laboratory tests mean that discussions around this parameter are a subject of controversy. [Aims] In this work, we aim to use meteor data obtained by the Fireball Recovery and InterPlanetary Observation to calculate the luminous efficiencies of the recorded meteors. We also show the limitations of the methods presented herein. [Methods] Deceleration-based formulas were used to calculate the masses of the pre-atmospheric meteoroids. These can in turn be compared to the meteor brightnesses to assess the luminous efficiencies of the recorded objects. Fragmentation of the meteoroids is not considered within this model. Good measurements of the meteor deceleration are required. [Results] We find τ-values, as well as the shape change coefficients, of 294 meteors and fireballs with determined masses in the range of 10-6-100 kg. The derived τ-values have a median of τmedian = 2.17%. Most of them are of the order of 0.1-10%. We present how our values are obtained, compare them with data reported in the literature, and discuss several methods. A dependence of τ on the pre-atmospheric velocity of the meteor, ve, is noticeable with a relation of τ = 0.0023 ve2.3. Furthermore, a dependence of τ on the initial meteoroid mass, Me, is found with negative linear behaviour in log-log space: τ = 0.48 Me-0.47. [Conclusions] The higher luminous efficiency of fast meteors could be explained by the higher amount of energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, the negative dependence of τ on Me implies that the radiation of smaller meteoroids is more efficient. The results of this study also show the limitations of the ablation-based model for the determination of the luminous efficiency.

Saturn’s Moon Phoebe has been suggested to originate from the Kuiper Belt. However, its density is twice that of Kuiper Belt objects (KBOs) in the same size class, which challenges that relationship. Since the internal evolution of mid-sized planetesimals (100–300 km in diameter) is primarily driven by the amount of accreted short-lived radioisotopes, it is possible to constrain the relative times of formation of these bodies based on their bulk porosity content, hence their densities. From modelling the thermal evolution of KBOs, we infer a difference in formation timing between these bodies and Phoebe. This confirms prior suggestions for a delayed accretion timeframe with increasing distance from the Sun. This geophysical finding combined with spectral observations suggests Phoebe formed in the same region as C-type asteroids and support recent dynamical models for a C-type body reservoir between the orbits of the giant planets. On the other hand, the similarly low densities of mid-sized D-type asteroids, Trojan asteroids, and KBOs add to the growing evidence that these objects shared a common reservoir near or beyond the orbit of Neptune and were heat starved overall.

International audience; In this White Paper (part I) we present an analysis of our current knowledge of Ice Giant systems in the light of six key science questions about planetary systems formulated in the ``Planetary Exploration, Horizon 2061'' long-term foresight exercise. We formulate measurement requirements and favored destinations for each of these science questions.

International audience; Starting from the six key science objectives for the exploration of planetary systems presented in part I of this White Paper, and from the corresponding measurement requirements for the future exploration of Ice Giants systems, we build a notional road map for a set of missions to these systems that will address most of these science objectives.

Spectroscopy in the visible and near-infrared has been the main tool for characterising the surface properties of asteroids for decades. For a given target, the two wavelength regimes are usually acquired by different telescopes/instruments, separated by years. They are seldom obtained simultaneously. However, it is not straightforward to combine datasets from different sources because of the spectral reddening linked with phase angle. We present the first-light result of SOVAG (Spectrographe pour l’Observations dans le Visible et infrarouge proche d’Asteroides Geocroiseurs), a new concept of spectrograph for observing both wavelength ranges at the same time. It is compact in design and portable. We developed a prototype of this instrument between 2016 and 2018. In July 2018, we mounted SOVAG on the 1 m-telescope in Pic du Midi observatory (for which it was designed) and conducted its on-sky first light experiment. We present a spectrum of (4) Vesta which demonstrates the reliability of observations and the accuracy of the calibration. Ongoing development will allow us to push observation-limits toward fainter objects.

The Japanese MMX sample return mission to Phobos by JAXA will carry a Rover developed by CNES and DLR that will be deployed on Phobos to perform in-situ analysis of the Martian moon's surface properties. Past images of the surface of Phobos show that it is covered by a layer of regolith. However, the mechanical and compositional properties of this regolith are poorly constrained. In particular nothing is known regarding the particle sizes, their chemical composition, the packing density of the regolith as well as other frictional parameters and surface dynamics from current remote images. Understanding the properties and dynamics of the regolith in the low-gravity environment of Phobos is important to trace back its history and surface evolution. Moreover, this information is also important to support the interpretation of data obtained by instruments onboard the main spacecraft and to minimize the risks involved in the sampling by the spacecraft. The instruments onboard the Rover are an infrared radiometer (miniRad), a Raman spectrometer (RAX), two cameras looking forwards for navigation and science purposes (NavCams), and two cameras observing the flow of regolith around the rover wheels (WheelCams). The Rover will be deployed before the sampling of Phobos' surface by MMX spacecraft and will be the first rover driving on a Martian moon and in a low-gravity environment.

The last thirty years of cosmochemistry and planetary science have shown that one major Solar System reservoir is vastly undersampled in the available suite of extra-terrestrial materials, namely small bodies that formed in the outer Solar System (>10 AU). Because various dynamical evolutionary processes have modified their initial orbits (e.g., giant planet migration, resonances), these objects can be found today across the entire Solar System as P/D near-Earth and main-belt asteroids, Jupiter and Neptune Trojans, comets, Centaurs, and small (diameter < 200 km) trans-Neptunian objects. This reservoir is of tremendous interest, as it is recognized as the least processed since the dawn of the Solar System and thus the closest to the starting materials from which the Solar System formed. Some of the next major breakthroughs in planetary science will come from studying outer Solar System samples (volatiles and refractory constituents) in the laboratory. Yet, this can only be achieved by an L-class mission that directly collects and returns to Earth materials from this reservoir. It is thus not surprising that two White Papers advocating a sample return mission of a primitive Solar System small body (ideally a comet) were submitted to ESA in response to its Voyage 2050 call for ideas for future L-class missions in the 2035-2050 time frame. One of these two White Papers is presented in this article., Experimental Astronomy, 54 (2-3), ISSN:0922-6435, ISSN:1572-9508

Two meteorite pieces have been recovered in Italy, near the town of Cavezzo (Modena), on 2020 January 4th. The associated fireball was observed on the evening of New Year’s Day 2020 by eight all-sky cameras of the PRISMA fireball network, a partner of FRIPON. The computed trajectory had an inclination angle of approximately 68° and a velocity at infinity of 12.8 km s−1. Together with the relatively low terminal height, estimated as 21.5 km, those values were indicating the significant possibility of a meteorite dropping event, as additionally confirmed by the non-zero residual total mass. The strewn-field was computed taking into account the presence of two bright light flashes, revealing that the meteoroid had been very likely subject to fragmentation. Three days after the event, two samples, weighing 3.1 and 52.2 g, were collected as a result of a dedicated field search and thanks to the involvement of the local people. The two pieces were immediately recognized as freshly fallen fragments of meteorite. The computed orbital elements, compared with the ones of known Near-Earth Asteroids from the NEODyS database, are compatible with one asteroid only; 2013 VC10. The estimated original mass of the meteoroid, 3.5 kg, and size, approximately 13 cm, is so far the smallest among the current 35 cases in which meteorites were recovered from precise strewn-field computation thanks to observational data. This result demonstrates the effectiveness of accurate processing of fireball network data even on challenging events generated by small size meteoroids.

Carri, B., et al., [Context] Dynamical models of Solar System evolution have suggested that the so-called P- and D-type volatile-rich asteroids formed in the outer Solar System beyond Neptune's orbit and may be genetically related to the Jupiter Trojans, comets, and small Kuiper belt objects (KBOs). Indeed, the spectral properties of P- and D-type asteroids resemble that of anhydrous cometary dust. Aims. We aim to gain insights into the above classes of bodies by characterizing the internal structure of a large P- and D-type asteroid. [Methods] We report high-angular-resolution imaging observations of the P-type asteroid (87) Sylvia with the Very Large Telescope Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. These images were used to reconstruct the 3D shape of Sylvia. Our images together with those obtained in the past with large ground-based telescopes were used to study the dynamics of its two satellites. We also modeled Sylvia's thermal evolution. [Results] The shape of Sylvia appears flattened and elongated (a/b 1.45; a/c 1.84). We derive a volume-equivalent diameter of 271 ± 5 km and a low density of 1378 ± 45 kg m-3. The two satellites orbit Sylvia on circular, equatorial orbits. The oblateness of Sylvia should imply a detectable nodal precession which contrasts with the fully-Keplerian dynamics of its two satellites. This reveals an inhomogeneous internal structure, suggesting that Sylvia is differentiated. [Conclusions] Sylvia's low density and differentiated interior can be explained by partial melting and mass redistribution through water percolation. The outer shell should be composed of material similar to interplanetary dust particles (IDPs) and the core should be similar to aqueously altered IDPs or carbonaceous chondrite meteorites such as the Tagish Lake meteorite. Numerical simulations of the thermal evolution of Sylvia show that for a body of such a size, partial melting was unavoidable due to the decay of long-lived radionuclides. In addition, we show that bodies as small as 130-150 km in diameter should have followed a similar thermal evolution, while smaller objects, such as comets and the KBO Arrokoth, must have remained pristine, which is in agreement with in situ observations of these bodies. NASA Lucy mission target (617) Patroclus (diameter ≈140 km) may, however, be differentiated., This work has been supported by the Czech Science Foundation through grants 20-08218S (J. Hanuš, J. Ďurech) and by the Charles University Research program No. UNCE/SCI/023. The work of TSR was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). This material is partially based upon work supported by the National Science Foundation under Grant No. 1743015.

The comparative study of planetary systems is a unique source of new scientific insight: following the six “key science questions” of the “Planetary Exploration, Horizon 2061” long-term foresight exercise, it can reveal to us the diversity of their objects (Question 1) and of their architectures (Question 2), help us better understand their origins (Question 3) and how they work (Question 4), find and characterize habitable worlds (Question 5), and ultimately, search for alien life (Question 6). But a huge “knowledge gap” exists which limits the applicability of this approach in the solar system itself: two of its secondary planetary systems, the ice giant systems of Uranus and Neptune, remain poorly explored. Starting from an analysis of our current limited knowledge of solar system ice giants and their systems in the light of these six key science questions, we show that a long-term plan for the space exploration of ice giants and their systems will greatly contribute to answer these questions. To do so, we identify the key measurements needed to address each of these questions, the destinations to choose (Uranus, Neptune, Triton or a subset of them), the combinations of space platform(s) and the types of flight sequences needed. We then examine the different launch windows available until 2061, using a Jupiter fly-by, to send a mission to Uranus or Neptune, and find that: (1) an optimized choice of platforms and flight sequences makes it possible to address a broad range of the key science questions with one mission at one of the planets. Combining an atmospheric entry probe with an orbiter tour starting on a high-inclination, low periapse orbit, followed by a sequence of lower inclination orbits (or the other way around) appears to be an optimal choice. (2) a combination of two missions to each of the ice giant systems, to be flown in parallel or in sequence, will address five out of the six key questions and establish the prerequisites to address the sixth one: searching for life at one of the most promising Ice Giant moons. (3) The 2032 Jupiter fly-by window, which offers a unique opportunity to implement this plan, should be considered in priority; if this window cannot be met, using the 2036 Jupiter fly-by window to send a mission to Uranus first, and then the 2045 window for a mission to Neptune, will allow one to achieve the same objectives; as a back-up option, one should consider an orbiter + probe mission to one of the planets and a close fly-by of the other planet to deliver a probe into its atmosphere, using the opportunity of a future mission on its way to Kuiper Belt Objects or the interstellar medium; (4) based on the examination of the habitability of the different moons by the first two missions, a third one can be properly designed to search for life at the most promising moon, likely Triton, or one of the active moons of Uranus. Thus, by 2061 the first two missions of this plan can be implemented and a third mission focusing on the search for life can be designed. Given that such a plan may be out of reach of a single national agency, international collaboration is the most promising way to implement it.

Visible near-infrared (Vis–NIR) reflectance spectroscopy is a powerful nondestructive technique allowing the parent bodies identification of cosmomaterials such as meteorites, micrometeorites, and interplanetary dust particles (IDPs) studied in the laboratory. Previous studies showed that meteorites do not represent the full diversity of the solar system small bodies. We present here an experimental setup we developed for measuring Vis–NIR microspectroscopy of individual IDPs. We acquired diffuse Vis–NIR reflectance spectra of 15 particles ranging 7–31 μm in size. We discuss the requirements, the abilities, as well as the limitations of the technique. For sizes smaller than 17 μm, the slopes increase with decreasing particles sizes, while for sizes larger than 17 μm, the slopes are randomly distributed. The visible reflectance levels do not appear to be affected by the size of the IDPs, and show a bimodal distribution. Among the studied particles, we identified an IDP (L2079C18) exhibiting a feature at 0.66 μm, which is similar to the one observed by remote sensing on the surface of hydrated asteroids. This is the first detection of a hydration band in the reflectance spectrum of an IDP that could indicate a possible link between hydrated IDPs with hydrated asteroid surfaces.

High angular resolution disc-resolved images of (7) Iris collected by VLT/SPHERE instrument are allowed for the detailed shape modelling of this large asteroid revealing its surface features. If (7) Iris did not suffer any events catastrophic enough to disrupt the body (which is very likely) by studying its topography, we might get insights into the early Solar system’s collisional history. When it comes to internal structure and composition, thoroughly assessing the volume and density uncertainties is necessary. In this work, we propose a method of uncertainty calculation of asteroid shape models based on light curve and adaptive optics (AO) images. We apply this method on four models of (7) Iris produced from independent Shaping Asteroids using Genetic Evolution and All-Data Asteroid Modelling inversion techniques and multiresolution photoclinometry by deformation. Obtained diameter uncertainties stem from both the observations from which the models were scaled and the models themselves. We show that despite the availability of high-resolution AO images, the volume and density of (7) Iris have substantial error bars that were underestimated in the previous studies., This work has been supported by the Czech Science Foundation through grant 20-08218S (JH, MB) and by the Charles University Research program No. UNCE/SCI/023. This work has been partially supported by Horizon 2020 grant no. 871149 ‘EPN-2024-RI’.

The last thirty years of cosmochemistry and planetary science have shown that one major Solar System reservoir is vastly undersampled in the available suite of extra-terrestrial materials, namely small bodies that formed in the outer Solar System (>10AU). Because various dynamical evolutionary processes have modified their initial orbits (e.g., giant planet migration, resonances), these objects can be found today across the entire Solar System as P/D near-Earth and main-belt asteroids, Jupiter and Neptune Trojans, comets, Centaurs, and small (diameter directly collects and returns to Earth materials from this reservoir. It is thus not surprising that two white papers advocating a sample returnmission of a primitive Solar System small body (ideally a comet) were submitted to ESA in response to its call for ideas for future L-classmissions in the 2035-2050 time frame. I will present an overview of the ideas listed in one of these two white papers and discuss how such amission would be complementary to current and future ground based observations of primitive Solar System small bodies.

The comparative study of the different planetary systems accessible to our observations is a unique source of new scientific insight: it can reveal to us the diversity of these systems and of the objects within them, help us better understand their origins and how they work, find and characterize habitable worlds, and ultimately, search for alien life in our galactic neighborhood. But, in the solar system itself, two of its secondary planetary systems, the ice giant systems, as well as their two main objects, Uranus and Neptune, remain poorly explored. We will present an analysis of our current limited knowledge of these systems in the light of six key science questions about planetary systems formulated in the “Planetary Exploration, Horizon 2061” long-term foresight exercise: (Q1) What is the diversity of planetary systems objects? (Q2) What is the diversity of their architectures? (Q3) What do we know of their origins and formation scenarios? (Q4) How do they work? (Q5) Do they host potential habitats? (Q6) Where and how to search for life? We will show that a long-term plan for the space exploration of ice giants and their systems, complemented by the combination of Earth and space-based observations, will provide major contributions to answers to these six questions. In order to do so, we identify the measurements that must be performed in priority to address each of these questions, the destinations to choose (Uranus, Neptune, Triton or a subset of them), and the combinations of space platform(s) (orbiter, atmospheric entry probe(s), lander…) and of flight sequences needed. Based on this analysis, we look at the different launch windows available until 2061, using a Jupiter fly-by, to send a mission to Uranus or Neptune and find that: (1) a single mission to one of the Ice giants, combining an atmospheric entry probe and an orbiter tour starting on a high-inclination, low-periapse orbit, followed by a sequence of lower- inclination orbits, at least at one of the planets, will make it possible to address a broad range of these key questions; (2) a combination of two well-designed missions to each of the ice giant systems, to be flown in parallel or in sequence, will make it possible to address five out of the six key questions, and to establish the prerequisites for addressing the sixth one. The 2032 Jupiter fly-by window offers a unique opportunity to achieve this goal; (3) if this window cannot be met, using the 2036 Jupiter fly-by window to send a mission to Uranus first, and then the 2045 window for a mission to Neptune, will achieve the same goals. As a back-up option, the feasibility of sending an orbiter + probe mission to one of the planets and using the opportunity of a mission on its way to the interstellar medium to execute a close fly-by of the other planet and deliver a probe into its atmosphere should be studied carefully; (4) based on the expected science return of the first two missions, a third mission focusing on the search for life at a promising moon, namely Triton based on our current knowledge, or perhaps one of the active moons of Uranus after due characterization, can be properly designed. By the 2061 horizon, the first two missions of this plan can be implemented and the design of a third mission focusing on the search for life can be consolidated. Given the likelihood that such a plan may be out of reach of a single national agency, international collaboration is the most promising way to implement it.

Introduction: Meteorites seem to come from a small number of primary parent bodies [1]. B-, C-, Cb-, Cg-, P- and D-types, representing not less than 66% of the mass of the main belt have no analogues clearly identified in the meteorite collections [2]. However, meteorites are not the only cosmomaterials found on Earth since no less than 30 000 tons of interplanetary dust particles (IDPs) enter the Earth’s atmosphere each year [3]. IDPs originate from different parent bodies throughout the solar system [4, 5, 6]. The link between IDPs and asteroids can be investigated thanks to Vis-NIR spectroscopy commonly used for the classification of asteroids (0.4 - 2.5 µm). The reflectance measurements in the visible range (0.4 - 0.8 μm) performed on IDPs in the 90s [7] and the simulated visible near infrared (Vis-NIR) spectra of IDPs with comparison of mid infrared (Mid-IR) spectra [2] have shown that IDPs may be good analogues to some asteroids and in particular to the classes not sampled by meteorites. But Vis-NIR reflectance measurements of IDPs is challenging and we must understand how the measurement on an isolated micro-metric particle can be affected by physical parameters of the sample such as size, composition, and roughness. We report here the requirements, the abilities as well as the limitations of the technique and the results obtained on 15 IDPs particles ranging 7-31 µm in size in the Vis-NIR range (0.45 - 1.0 µm). Experiments: Our setup, installed in a clean room, consists of a Vis-NIR spectrometer (Maya2000 Pro from Ocean Optics) coupled to a macroscope (Leica Z16 APO). A Vis-NIR optical fiber (100 or 50 μm in diameter) is used to collect the light diffused by the sample which is unilaterally illuminated by a halogen source through a 1000 μm diameter fiber (phase angle of ~ 45°). By changing the magnification and/or the diameter of the collection fiber it is possible to adapt the collection spot to the grain size down to 7 μm size. Results and discussion: To obtain a reliable reflectance spectrum of a micro-metric grain with this setup, we show that it is necessary to average spectra taken at different azimuth angles, by rotating the particle several times in the observation plane with respect to the incident light. Based on the study of spectral slopes we found that for particles with sizes below ~ 17 µm the spectral slope increases linearly with decreasing particle sizes. This behavior is due to a bias encountered in the reflectance measurement in this size range, inducing thus a loss of the chemical information. For particle sizes larger than ∼ 17 µm the spectral slopes seem randomly distributed between ∼ -0.3 and 0.4 µm−1, and the spectra must therefore carry chemical information of the particles. We found that the visible reflectance levels of the IDPs show a multimodal distribution. There is a lack of IDPs with reflectance level ~ 5 and ~ 8%. In addition, the majority of IDPs have rather low reflectance levels (< 10%). Some particles have reflectance levels that may be influenced by the presence of magnetite, which is sometimes found in extraterrestrial materials and could form upon atmospheric entry. Among the studied particles we identified an IDP (L2079C18) exhibiting a feature at 0.66 µm which is similar to the one observed by remote sensing at the surface of hydrated asteroids. This is the first detection of a hydration band in the reflectance spectrum of an IDP which could indicate a possible link between hydrated IDPs with hydrated asteroid surfaces. Acknowledgments: We are grateful to the CAPTEM NASA for providing the IDPs. This work is supported by the Programme National de Planétologie (PNP) of CNRS/INSU, co-funded by CNES. The authors also thank the ANR RAHIIA SSOM and the P2IO LabEx (ANR-10-LABX0038) in the framework Investissements d’Avenir (ANR11-IDEX-0003-01) for their supports. We thank O. Mivumbi and Y. Longval for their help and technical support for the development of the device. References: [1] R. Greenwood et al. (2020) Geochimica et Cosmochimica Acta 277, 377-406. [2] P. Vernazza et al. (2015) The Astrophysical Journal 806 :204. [3] Love and Brownlee. (1993) Science, 262, 550-553. [4] Dermott et al. (1994) Nature, 369, 719-723. [5] Liou et al. (1996) Icarus, 124, 429-440. [6] Brunetto et al. (2011) Icarus, 212, 896-910. [6] Bradley, J. P. (2003) Treatise on Geochemistry, 1, 689. [7] Bradley, et al. (1996) Meteoritics & Planetary Science, 31, 394-402.

Introduction Asteroid (16) Psyche is the largest M-type asteroid in the main belt and the only metal rich asteroid of this size (D > 200 km). It has been proposed that Psyche could be an exposed planetary core [S17,D18]. This hypothesis and the uniqueness of Psyche's characteristics are the main reasons for its selection as the rendez-vous target of a NASA Discovery mission that is scheduled to launch in 2022 [E17]. However, the true nature of Psyche remains enigmatic which leads to the formulation of several distinct formation scenarios. Psyche’s density appears compatible with that of stony-iron meteorites such as mesosiderites [Vi18] as well as that of pallasites and CB chondrites [E20]. It is also unknown if its interior is intact or a is a rubble pile and if it is differentiated. Observation We obtained 35 images of Psyche at 7 epochs in July and August 2019 using VLT/SPHERE/ZIMPOL. They complement the first 25 images obtained in 2018 that were already presented in [Vi18], for a total of 60 images taken at 12 epochs. Psyche was observed near opposition with a pixel size corresponding to ~6 km/px. The first apparition in 2018 was limited to the northern hemisphere of Psyche but the second apparition in 2019 covered well the equatorial region and allowed us to achieve a complete coverage of the surface. Methods First, we generated an updated shape model of Psyche with the ADAM inversion algorithm [Vi15]. We used the same procedure as in [Vi18] and added the new SPHERE images and a new stellar occultation recorded in October 2019. We then applied our Multi-resolution PhotoClinometry by Deformation (MPCD; [C13]) method on a selection of the SPHERE images to reconstruct the 3D shape of Psyche. The MPCD software gradually deforms the vertices of an initial mesh to minimize the difference between the observed images and realistic images of the surface. The ADAM model was used as input for the initial mesh and the spin parameters. Results and conclusions The ADAM and MPCD shape models are remarkably similar with a small volume difference and radial differences mean. The comparison between the SPHERE images and the corresponding synthetic images is given in Fig. 1. The densities derived from the volumes of both shape models combined with the average of available mass estimates are close to ~4 g/cm³ which is in agreement with other recent estimates [S17,D18,Vi18]. A shape analysis was performed by computing the radial differences between Psyche’s shape model and its best-fitting ellipsoid to obtain the average residuals relative to the mean radius. We then computed the sphericity index of Psyche using the same approach as in [V19]. We repeated the process for other large main-belt asteroids, the terrestrial planets and smaller asteroids visited in-situ by space missions. It revealed that Psyche’s shape appears intermediate between those of larger asteroids and those of smaller or similarly sized bodies. Psyche’s appearance is close to an ellipsoid with flat regions at the poles even though we identified three depression regions along its equator. Finally, we investigated whether the shape of Psyche may be close to the equipotential shape of an hydrostatic body. The flatness and density of Psyche are compatible with a formation at hydrostatic equilibrium as a Jacobi ellipsoid with a shorter rotation period of ~3 h. Later impacts may have slowed down Psyche’s rotation, which is currently ~4.2 h, while also creating the imaged depressions. Our results open the possibility that Psyche acquired its primordial shape either after a giant impact while its interior was already frozen or while its interior was still molten owing to the decay of the short-lived radionuclide 26Al. Figure 1: Comparison between VLT/SPHERE/ZIMPOL deconvolved images of Psyche (top row) and the corresponding synthetic images of our MPCD (second row) and ADAM (third row) shape models. The red arrows indicate the direction of the spin axis. Bibliography [C13] Capanna, C., Gesquière, G., Jorda, L., Lamy, P., & Vibert, D. 2013, The Visual Computer, 29, 825 [D18] Drummond, J. D., Merline, W. J., Carry, B., et al. 2018, Icarus, 305, 174 [E17] Elkins-Tanton, L. T., Asphaug, E., Bell, J. F., et al. 2017, in Lunar and Planetary Science Conference, Lunar and Planetary Science Conference, 1718 [E20] Elkins-Tanton, L., Asphaug, E., Bell, J., et al. 2020, Journal of Geophysical Research: Planets [S17] Shepard, M. K., Richardson, J., Taylor, P. A. et al. 2017, Icarus, 281, 388 [V19] Vernazza, P., Jorda, L., Ševecek, P., et al. 2019, Nature Astronomy, 477 [Vi15] Viikinkoski, M., Kaasalainen, M., & ˇ Durech, J. 2015, A&A, 576, A8 [Vi18] Viikinkoski, M., Vernazza, P., Hanuš, J., et al. 2018, A&A, 619, L3

Aims. Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event. Methods. The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models. Conclusions. Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne's diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne - S/2019 (31) 1 - that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m-3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation., This work has been supported by the Czech Science Foundation through grant 18-09470S (J. Hanuš, O. Chrenko, P. Ševecˇek) and by the Charles University Research program No. UNCE/SCI/023. M.B. was supported by the Czech Science Foundation grant 18-04514J. Computational resources were supplied by the Ministry of Education, Youth and Sports of the Czech Republic under the projects CESNET (LM2015042) and IT4Innovations National Supercomputing Centre (LM2015070). P. Vernazza, A. Drouard, M. Ferrais and B. Carry were supported by CNRS/INSU/PNP. M.M. was supported by the National Aeronautics and Space Administration under grant No. 80NSSC18K0849 issued through the Planetary Astronomy Program. The work of TSR was carried out through grant APOSTD/2019/046 by Generalitat Valen-ciana (Spain). This work was supported by the MINECO (Spanish Ministry of Economy) through grant RTI2018-095076-B-C21 (MINECO/FEDER, UE). The research leading to these results has received funding from the ARC grant for Concerted Research Actions, financed by the Wallonia-Brussels Federation. TRAPPIST is a project funded by the Belgian Fonds (National) de la Recherche Scientifique (F.R.S.-FNRS) under grant FRFC 2.5.594.09.F. TRAPPIST-North is a project funded by the Université de Liège, and performed in collaboration with Cadi Ayyad University of Marrakesh. E. Jehin is a FNRS Senior Research Associate.

To answer key scientific questions about Planetary Systems, it is particularly fruitful to study the Jupiter System, the most complex “secondary” planetary system in the solar system, using the power of in situ exploration. Two key questions should be addressed by future missions:A-How did the Jupiter System form? Answers can be found in the most primitive objects of the system: Callisto seems to have been only partly differentiated; its bulk composition, interior and surface terrains keep records of its early eons; the 77 or so irregular satellites, wandering far out beyond the region occupied by the Galilean satellites, are unique and precious remnants of the populations of planetesimals which orbited the outer Solar System at the time of Jupiter’s formation.B-How does it work? One can address this question by studying and understanding the chain of energy transfer operating today in the Jupiter System: how is gravitational energy from Jupiter transferred to Io’s interior via tidal heat dissipation to power its volcanic activity? How does this activity in turn store energy into the Io plasma torus to drive the whole magnetosphere into motion? How does the interplay between the Io torus and the solar wind dump energy into heating of Jupiter’s upper atmosphere, or release it into the tail and interplanetary space?Starting from the measurement requirements derived from these two objectives, we propose two ambitious mission scenarios, named JCO and JSO, to meet these requirements. Both use the combination of a main spacecraft and one or several specialized small platforms.JCO, the Jupiter Callisto Orbiter, first flies by and characterizes several irregular satellites during its Jovian orbital tour. It is then injected into Callisto orbit to characterize its surface and interior, investigate its degree of differentiation and search for the possible existence of an internal ocean. As an option, JCO could release a lander to Callisto’s surface to perform key measurements of chemical composition, clues to understanding the formation scenario of the Galilean moons.JSO, the Jupiter System Observer, performs several fly-bys of Io and visits several irregular satellites during its Jovian orbital tour. As an option, JSO could release one or several small satellites to perform multi-point studies of the dynamics of the Jovian magnetosphere. At the end of its tour it could be injected into a halo orbit around the L1 Lagrangian point of the Sun-Jupiter system to monitor the solar wind upstream of the Jovian magnetosphere, measure Jovian seismic oscillations, and perform a comprehensive survey of the irregular satellites.Led by China under the name of GAN De, the first astronomer to have claimed an observation of a moon of Jupiter four centuries BC, and broadly open to international collaboration, a mission flying to Jupiter in the 2030’s according to either one of these scenarios will be able to capitalize on the legacy of previous missions to Jupiter (Juno, JUICE, Europa Clipper) and to trigger a very exciting international collaboration to unravel the mysteries of the origins and workings of the Jupiter system.

On May 30th, 2017 at about 21h 09m 17s UTC a green bright fireball crossed the sky of north-eastern Italy. The fireball path was observed from some all-sky cameras starting from a mean altitude of $81.1 \pm 0.2$ km (Lat. $44.369^{\circ} \pm 0.002^{\circ}$ N; Long. $11.859^{\circ} \pm 0.002^{\circ}$ E) and extinct at $23.3 \pm 0.2$ km (Lat. $45.246^{\circ} \pm 0.002^{\circ}$ N; Long. $12.046^{\circ} \pm 0.002^{\circ}$ E), between the Italian cities of Venice and Padua. In this paper, on the basis of simple physical models, we will compute the atmospheric trajectory, analize the meteoroid atmospheric dynamics, the dark flight phase (with the strewn field) and compute the best heliocentric orbit of the progenitor body. Search for meteorites on the ground has not produced any results so far., 19 pages, 17 figures. Accepted for publication in The European Physical Journal PLUS

Recent high-contrast imaging surveys, looking for planets in young, nearby systems showed evidence of a small number of giant planets at relatively large separation beyond typically 20 au where those surveys are the most sensitive. Access to smaller physical separations between 5 and 20 au is the next step for future planet imagers on 10 m telescopes and ELTs in order to bridge the gap with indirect techniques (radial velocity, transit, astrometry with Gaia). In that context, we recently proposed a new algorithm, Keplerian-Stacker, combining multiple observations acquired at different epochs and taking into account the orbital motion of a potential planet present in the images to boost the ultimate detection limit. We showed that this algorithm is able to find planets in time series of simulated images of SPHERE even when a planet remains undetected at one epoch. Here, we validate the K-Stacker algorithm performances on real SPHERE datasets, to demonstrate its resilience to instrumental speckles and the gain offered in terms of true detection. This will motivate future dedicated multi-epoch observation campaigns in high-contrast imaging to search for planets in emitted and reflected light. Results. We show that K-Stacker achieves high success rate when the SNR of the planet in the stacked image reaches 7. The improvement of the SNR ratio goes as the square root of the total exposure time. During the blind test and the redetection of HD 95086 b, and betaPic b, we highlight the ability of K-Stacker to find orbital solutions consistent with the ones derived by the state of the art MCMC orbital fitting techniques, confirming that in addition to the detection gain, K-Stacker offers the opportunity to characterize the most probable orbital solutions of the exoplanets recovered at low signal to noise., Comment: Astronomy & Astrophysics accepted, 13 Pages, 11 Figures

The Japan Aerospace Exploration Agency, JAXA, Martians Moons eXploration (MMX) mission will investigate the Martian Moons Phobos and Deimos, and return samples from Phobos to Earth. As part of this mission a small (~25 kg) rover, contributed by the Centre National d’Etudes Spatiales (CNES) and the German Aerospace Center (DLR), with additional contributions from INTA (Spain) and JAXA, will be delivered to the surface of Phobos. The rover will demonstrate the technology of locomotion on a regolith-covered, low gravity planetary surface. In addition, the rover will provide scientific data on the regolith properties (mechanical, mineralogical and thermal), provide ground truth for the MMX orbiter instruments, give context information for the returned samples, and contribute to reducing the risk of the landing and sampling operations of the MMX mission. In order to achieve these goals, the rover has a small suite of scientific instruments: a Raman spectrometer (RAX) to measure the mineralogical composition of the surface material, a radiometer (miniRAD) to measure the surface brightness temperature and determine thermal properties of both regolith and rocks (if in the field of view), a stereo pair of navigation cameras looking forwards (NAVCam) that will place constraints on the level of heterogeneity of the regolith both in terms of composition and space weathering alteration, and two cameras looking at the interface between wheel and surface (WheelCam). The WheelCams will observe the properties of the regolith compaction and flow around the wheels, and the resulting trenches in order to characterise the mechanical properties of the regolith itself. The MMX rover will be deployed from the main spacecraft from an altitude of less than 100 m above the surface of Phobos. The uprighting and deployment (legs/wheels and solar panels) sequences will be performed automatically once the rover comes to rest on the surface. The rover will then operate for 100 days covering a total distance of several meters to hundreds of meters. The MMX launch is currently planned for late 2024 with the Mars orbit insertion occurring in 2025, and the rover delivery and operations in 2026 or 2027. This presentation will provide an overview of the MMX rover and the expected science return from each of the four instruments.

et al., Asteroid (2) Pallas is the largest main-belt object not yet visited by a spacecraft, making its surface geology largely unknown and limiting our understanding of its origin and collisional evolution. Previous ground-based observational campaigns returned different estimates of its bulk density that are inconsistent with one another, one measurement1 being compatible within error bars with the icy Ceres (2.16 ± 0.01 g cm−3)2 and the other3 compatible within error bars with the rocky Vesta (3.46 ± 0.03 g cm−3)4. Here we report high-angular-resolution observations of Pallas performed with the extreme adaptive optics-fed SPHERE imager5 on the Very Large Telescope. Pallas records a violent collisional history, with numerous craters larger than 30 km in diameter populating its surface and two large impact basins that could be related to a family-forming impact. Monte Carlo simulations of the collisional evolution of the main belt correlate this cratering record to the high average impact velocity of ~11.5 km s−1 on Pallas—compared with an average of ~5.8 km s−1 for the asteroid belt—induced by Pallas’s high orbital inclination (i = 34.8°) and orbital eccentricity (e = 0.23). Compositionally, Pallas’s derived bulk density of 2.89 ± 0.08 g cm−3 (1σ uncertainty) is fully compatible with a CM chondrite-like body, as suggested by its spectral reflectance in the 3 μm wavelength region6. A bright spot observed on its surface may indicate an enrichment in salts during an early phase of aqueous alteration, compatible with Pallas’s relatively high albedo of 12–17% (refs. 7,8), although alternative origins are conceivable., Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 199.C-0074 (principal investigator: P.V.). This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with NASA. M.M. was supported by the National Aeronautics and Space Administration under grant number 80NSSC18K0849 issued through the Planetary Astronomy Program. This work was supported by the French Direction Générale de l’Armement (DGA) and Aix-Marseille Université (AMU). P.V., A.D. and B.C. were supported by CNRS/INSU/PNP. J.H., J.D. and P.S. were supported by the grant 18-09470S of the Czech Science Foundation and by the Charles University Research Programme number UNCE/SCI/023. M.Brož was supported by the grant 18-04514J of the Czech Science Foundation. E.J. is a F.R.S.-FNRS Senior Research Associate. The work of T.S.-R. was carried out through grant APOSTD/2019/046 by Generalitat Valenciana (Spain). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 730890.