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The study of small bodies in our solar system is fundamental for understanding its youth and evolution. These "primitive" bodies are "undifferentiated" (their components did not separate according to their density, irreversibly altering their mineralogy). They have evolved very little since their birth, spurring a composition relatively close to that of the primordial proto-planetary disk (Scott et al. 2018). However, other processes such as thermal alteration, aqueous alteration, shocks, or space weathering can affect these bodies’ surfaces. This may introduce certain compositional biases in remote-sensed data focusing on the surface of these bodies. Therefore, it is paramount to understand the processes affecting the surface of primitive asteroids to correctly assess their composition.There are several ways to study the surface of primitive asteroids, such as remotely, by acquiring spectroscopic data (gaining access to surface chemical and mineralogical composition). It is also possible to study these bodies in a laboratory environment, by working on analogous materials such as certain classes of "primitive" meteorites (Greenwood et al. 2020) (carbonaceous chondrites), on terrestrial analogues such as hydrated silicates - which dominates the mineral composition of “primitive” bodies (Usui et al. 2018), or directly on extra-terrestrial materials brought back by sample return missions (Yokoyama et al. 2022, Nakalura et al. 2022, Noguchi et al. 2022).In this work, we replicate in a laboratory environment the effects of space weathering (SpWe) on the surface of primitive asteroids. We focus on the effects of solar wind, the dominant SpWe process on "young" surfaces (Brunetto et al. 2015, Clark et al. 2002). We have chosen three terrestrial minerals analogous to a "primitive" surface - three hydrated minerals (two serpentines and one saponite) - of which we have produced several pellets which have been bombarded using He and Ar ions. In doing so, we made analogous materials of weathered primitive surface matter. These analogues were then characterized by infrared spectroscopy, from the visible to the far-infrared range, to study chemical changes prompted by ion bombardment. This was done by investigating how certain spectroscopic features – characteristic of hydrated silicates – changed upon ion-bombardment. We detected several effects, such as darkening in the visible range, visible slope reddening and bluing as well as a systematic shift towards longer wavelength affecting the position of several spectroscopic features.This was followed by a study at a smaller scale, using electron microscopy. We first characterized the surface of our weathered analogues using scanning electron microscopy, and then investigated the morphological and physicochemical changes taking place in the bombarded layer, at a nanometre scale, using transmission electron microscopy. Strong vesiculation effects of various kinds were identified in the ion bombarded amorphized layers, as well as textural changes and some elemental concentration evolution (such as the loss of oxygen in the utmost top surfaces, preferential amorphization of magnesium, etc.).The coupling between these two techniques, Vis/IR spectroscopy and electron microscopy, has allowed us to start probing the relations between SpWe induced effects seen at different scales.

International audience; In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS-REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X-ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3-D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3-D structure and porosity, and the detection of mineral and organic phases, and their spatial co-localization in 3-D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.

In this paper, we report the results of a campaign of measurements on four fragments of the CM Aguas Zarcas (AZ) meteorite, combining X‐ray computed tomography analysis and Fourier‐transform infrared (FT‐IR) spectroscopy. We estimated a petrologic type for our sampled CM lithology using the two independent techniques, and obtained a type CM2.5, in agreement with previous estimations. By comparing the Si‐O 10‐µm signature of the AZ average FT‐IR spectra with other well‐studied CMs, we place AZ in the context of aqueous alteration of CM parent bodies. Morphological characterization reveals that AZ has heterogeneous distribution of pores and a global porosity of 4.5 ± 0.5 vol%. We show that chondrules have a porosity of 6.3 ± 1 vol%. This larger porosity could be inherited due to various processes such as temperature variation during the chondrule formation and shocks or dissolution during aqueous alteration. Finally, we observed a correlation between 3D distributions of organic matter and mineral at micrometric scales, revealing a link between the abundance of organic matter and the presence of hydrated minerals. This supports the idea that aqueous alteration in AZ’s parent body played a major role in the evolution of the organic matter.

International audience; Many asteroids in the main belt have spectra like those of Mighei-type CM chondrites, but some Near Earth Objects (NEO) resemble less well known types of C2 chondrite. Northwest Africa (NWA) 12563, a new find with affinities to C2 chondrites, could help us understand the differences between observations of CM2 chondrites and bodies that are currently being studied by the Hayabusa2 and OSIRIS-REx space missions. NWA 12563 contains 14% chondrules supported by 86% fine grained matrix consistent with CM2 chondrites, but differs from them in other respects. In both matrix and chondrules, olivine is unaltered and pyroxene shows incipient alteration. Metal in chondrules is pseudomorphed by serpentine, and mesostasis is replaced by serpentine-saponite and chlorite. Many Type I chondrules have highly irregular shapes resulting from fracturing and selective metal replacement. Type II porphyritic chondrules are clusters of phenocrysts set in matrix-like material. Type II chondrules may be kinked and partially disbarred. The matrix of NWA 12563 differs from CM2 chondrites in the absence of tochilinite-cronstedtite intergrowths. It contains hydrated and oxidized amorphous silicate (Fe3+/∑Fe ~75%) richer in magnesium than in other chondrites (with embedded sulfides). Serpentine-saponite is also present, as well as abundant framboidal magnetite.NWA 12563 has similarities to a number of ungrouped magnetite-rich and 18O-rich chondrites (Bells, Essebi, Niger I, WIS 91600, Tagish Lake, and MET 00432) that we call C2-ung1, as opposed to C2-ung2 chondrites (poorer in 18O and magnetite). The oxygen isotopic composition coupled with a magnetic susceptibility of log χ = 4.67 places NWA 12563 with these ungrouped chondrites in a cluster distinct from CM2 chondrites. NWA 12563 is closest to WIS 91600 among the C2-ung1 chondrites in alteration style and light element compositions. WIS 91600, however, has suffered light thermal metamorphism, suggesting that NWA 12563 might represent its altered but unheated precursor material within the same parent body if it were zoned. The average Vis-NIR spectrum of NWA 12563 matches the asteroid taxonomic class K and resembles that of CO3 Frontier Mountain (FRO) 95002, but its spectra range from very “red” in dark matrix areas and very “blue” in magnetite-rich areas. The average MIR spectrum shows features indicating phyllosilicates, aliphatic CH compounds, hydrated silicates, and olivine. It is significantly different from those of other chondrites including FRO 95002, and closest to Bells (from which it differs in carbon isotopic composition) and WIS91600. The variety of mineralogical, chemical and isotopic properties among C2-ung1 chondrites requires several different parent bodies. However, the high abundance of magnetite common to this cluster of ungrouped chondrites, and to a lesser extent CI chondrites, indicates that they should be considered as possible material from Bennu, which has an 18 µm magnetite signal in its spectrum not seen in the CM2 chondrites (Hamilton et al., 2019).

Since the pioneer lunar sample return missions, the development of advanced techniques for the laboratory analysis of retrieved samples has run in parallel with the advances in space studies. All along the last decades, a common goal of these developments has been to maximize the scientific outcomes of laboratory studies while minimizing the loss of precious extraterrestrial samples. We provide an overview of the techniques and instruments used so far to analyze, characterize and study returned extraterrestrial samples. Considering the limited amount of material that is retrieved by the space missions, a multi-analytical sequence from less destructive techniques to more destructive techniques needs to be established. The return of Hayabusa2 and OSIRIS-REx samples will probably trigger a wave of laboratory studies, which, in turn, will support new developments of space instruments for observations of Solar System bodies.

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.

Cosmic rays, solar wind and solar energetic particles induce changes in the physical structure and chemical composition of frozen volatiles on the surface solar system outer objects, such as satellites of giant planets, centaurs and Kuiper-belt objects (e.g., Johnson 1990, Strazzulla et al. 2003, Urso et al. 2020). Such energetic particles can be responsible for the formation of C-rich refractory materials that determine the appearance of red slopes in the visible and near-infrared spectra of small bodies (e.g., Brunetto et al. 2006, Brown et al. 2011). Laboratory experiments performed to simulate the irradiation of frozen surfaces in space show that energetic ions or electrons (keV-MeV) determine the formation of new species, not present in the original samples (e.g., Rothard et al. 2017). The subsequent warm-up of processed mixtures causes both the sublimation of volatile compounds and an increase in the molecular diffusion and reactivity. As a consequence, the chemical complexity increases and organic refractory residues are formed. Residues are thought to be representative of the refractory materials on the surface of outer bodies as well as of cometary materials and a possible precursor of the soluble organic matter (SOM) found in meteorites (e.g., Strazzulla & Johnson 1991, Munoz-Caro & Schutte 2003, Brunetto et al. 2006, Danger et al. 2013, Baratta et al 2015, Urso et al. 2017, Poston et al. 2018}. We present recent laboratory experiments to produce and characterize organic refractory residues produced after ion irradiation of frozen volatiles. Water, methanol and ammonia mixtures in ratios 1:1:1 and 3:1:1 are deposited at 15 K and exposed to 40 keV H+ by means of the INGMAR setup (Urso et al. 2020). After irradiation, mixtures are warmed up with a constant heating rate and organic refractory residues are formed at 300 K. Throughout the experiment, we monitor the sample evolution by means of in-situ infrared transmission spectroscopy (4000-700 cm-1, 2.5-13.3 µm). After warmup, organic refractory residues are recovered from the irradiation chamber and are further characterized through ex-situ Very High Resolution Mass Spectrometry. The combination of both techniques allows to shed light on the composition of irradiated frozen volatiles and of residues. We also search for specific molecules by means of tandem Mass Spectrometry/High Resolution Mass Spectrometry. Furthermore, we compare the chemical composition of our samples with that of organic refractory residues produced after UV photolysis of volatile mixtures. Our results give information on the effects induced by different experimental parameters (dose, mixture ratio) on the composition of organic refractory materials. In particular, we investigate the effects of increasing irradiation dose in the elemental abundance and in the Double Bond Equivalent (DBE) of residues. We also give the timescales necessary to observe in solar system outer objects the effects revealed in laboratory experiments, and we discuss the role of the various sources of processing (cosmic rays, solar wind, solar energetic particles) in determining changes in the chemical composition of frozen surfaces in space. Our work supports the interpretation of space mission data and astronomical observations of comets and solar system outer objects as well as of star-forming regions in the Interstellar medium, where cosmic rays bombard icy grain mantles and thus play a role in the synthesis of complex organic molecules in the early stage of star-formation. Acknowledgements This work is supported by the CNES-France. INGMAR (IAS-CSNSM, Orsay) is funded by the French Programme National de Planétologie (PNP), Faculté des Sciences d'Orsay, Université Paris-Sud (Attractivité 2012), French National Research Agency ANR (contract ANR-11-BS56-0026, OGRESSE), P2IO LabEx (ANR-10-LABX-0038) in the framework Investissements d'Avenir (ANR-11-IDEX-0003-01). We thank the support from RAHIIA SSOM (ANR-16-CE29-0015). R.G.U. thanks the CNES postdoctoral program. References:Baratta, G. A., Chaput, D., Cottin, H., et al. 2015, Planetary and Space Science, 211 Brunetto, R., Barucci, M. A., Dotto, E., Strazzulla, G. 2006, ApJ, 644, 646 Brown, M. E. Schaller, E. L., Fraser, W. C. 2011, ApJ Letters, 739, L60 Danger, G., Orthous-Daunay, F. R., de Marcellus, P., et al. 2013, GeoCoA, 118, 184 Johnson, R. E., 1990, Energetic charged-particle interactions with atmospheres and surfaces Munoz Caro, G. M., Schutte, W. A. 2003, A&A, 412, 121 Poston, M. J., Mahjoub, A., Ehlmann, B. L., et al. 2018, ApJ, 856, 124 Rothard, H., Domaracka, A., Boduch, P. et al. 2017, Journal of Physics B, 50, 062011 Strazzulla, G., & Johnson, R. E. 1991, Irradiation Effects on Comets and Cometary Debris, Comets in the post-Halley era (Dordrecht: Springer Netherlands) Strazzulla, G., Cooper, J. F., Christina, E. R., Johnson, R. E., 2003, Comptes Rendus Physique, 4, 7, 791 Urso, R. G., Scirè, C., Baratta, G. A., et al. 2017, PCCP, 19, 21759 Urso, R. G. Baklouti, D., Djouadi, Z., Pinilla-Alonso, N., Brunetto, R. 2020, ApJ Letters, 894, 1, L3

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.

1. Introduction The Hayabusa2/JAXA spacecraft has orbited and studied near-Earth object Ryugu [1]. Two sample collections have been performed and the spacecraft is currently on its way back to the Earth for an expected return in late 2020. A preliminary examination phase will follow [2], expected to elucidate the formation and evolution of Ryugu. Considering the limited amount of material that will be retrieved, a multi-analytical sequence is needed to maximize the scientific outcome and minimize sample loss. Among the possible laboratory techniques, IR spectroscopy is important in being totally non-destructive and comparable to remote sensing observations of small bodies [3]. Thanks to IR imaging micro-spectroscopy, it is possible to detect and study the spatial distribution of molecular bonds associated to minerals, water and organic compounds, and their co-localization [4]. We consider IR three dimensional (3D) micro-tomography (IR-CT) an excellent starting point in a multi-analytical sequence to be applied on returned samples [5]. Here we report IR hyperspectral measurements of carbonaceous chondrites as a rehearsal of IR-CT and IR hyperspectral imaging that will be part of the multi-analytical sequence of the “MIN-PET CG” Hayabusa2 team (mineralogy and petrology of coarse grains) led by T. Nakamura. 2. Methods We performed IR measurements in reflectance on bulk fragments of selected meteorites, and both in reflectance and transmittance on several isolated grains (sizing 20-50 µm) extracted from carbonaceous chondrites. We also analyzed individual grains of the Murchison CM meteorite prepared at Tohoku University (Japan) from three bulk samples: (1) unheated, (2) heated at 400°C, and (3) heated at 600°C [6]. The laboratory-controlled heating was applied to simulate potential heating undergone by Ryugu surface materials, as suggested by some Hayabusa2 observations [7]. Some of these Murchison grains were mounted on tungsten needles by means of a platinum welding performed in IEMN-Lille (France) with a focused ion beam microscope. Other grains were prepared at Tohoku University, mounted on carbon fibers using epoxy (Fig. 1). We analyzed the samples using an IR hyperspectral imaging and micro-tomography setup installed at the SMIS beamline of the SOLEIL synchrotron (France). This setup has already been used for analyzing Hayabusa samples from asteroid Itokawa [8]. FTIR data were collected using an Agilent Cary 670/620 microspectrometer. In transmission mode we used a X25 objective coupled with high magnification optics (providing an additional X2.5 magnification) placed in front of a 128x128 pixels FPA detector, to obtain a projected pixel size of ~0.66 µm on the focal plane, and a field of view of ~84 µm. IR-CT is performed in transmission mode using the method described by Dionnet et al. [8]. In reflection mode we used a X15 objective, with a projected pixel size of ~5.5 µm on the focal plane, and a field of view of ~700 µm (Fig. 1). In both cases we collected hyperspectral data: for each pixel we obtained an IR spectrum in the 850-3950 cm-1 spectral range. The spatial resolution was diffractionlimited for the whole investigated spectral range. 3. Results Infrared spectra show the presence of bending and stretching absorption bands of chemical bonds (C-H, OH, Si-O, C=O, etc.) of different functional groups, as expected from literature IR spectra of Murchison and other chondrites [9,10]. The relative intensities of these bands are found to vary among different grains, and their 3D spatial distribution is heterogeneous within individual grains (see Fig. 1). Noticeable differences are found between the IR spectra of unheated and heated Murchison samples, with a general trend of increasing the anhydrous to hydrated silicate content with increasing temperature, and reducing the organic content. Fig. 1. A typical IR reflectance hyperspectral map of an unheated Murchison sample mounted on a carbon needle (top left, microscope images in bright and dark field), with the detection of hydrated (bottom left) and anhydrous (bottom right) areas. The epoxy contribution can be clearly separated (top right). 4. Summary and Conclusions IR data provide a first quick look at the composition, abundance and 3D distribution of mineral phases and carbonaceous materials at the scale of a few micrometers. Once regions of interest are identified by IR measurements, thin sliced sections of the samples can be analyzed by more destructive techniques to retrieve the structure and the elemental and isotopic composition of the carbonaceous component and its mineral host, down to the nanometer scale [11]. In addition, the IR data are useful in the comparison with remote sensing observations of asteroid surfaces [7,12]. This top-down sequence will help us building a bridge between the remote sensing and in situ observations of Ryugu at macroscopic scale and the chemical and physical processes operating at the nanoscale. Acknowledgments The micro-spectroscopy measurements were supported by grants from Region Ile-de-France (DIM-ACAV) and SOLEIL. This work has been funded by the CNES (France) and by the ANR project CLASSY (Grant ANR-17-CE31-0004-02) of the French Agence Nationale de la Recherche. This work was partly supported by the French RENATECH network. References [1] Watanabe S. et al. (2019) Science 364, 268-272. [2] Tachibana S. et al. (2018) AGU Fall Meeting, abstract #P33C-3846. [3] Brunetto R. et al. (2011) Icarus 212, 896–910. [4] Dionnet Z. et al. (2018) Meteoritics & Planet. Sci. 53, 2608-2623. [5] Dionnet Z. et al. (2018) Microscopy and Microanalysis 24, 2100-2101. [6] Mogi K. et al. (2017) 80th Annual Meeting of the Meteoritical Society, Abstract #6225. [7] Kitazato K. et al. (2019) Science 364, 272-275. [8] Dionnet Z. et al. (2020) Meteoritics & Planet. Sci., in press. [9] Lantz C. et al. (2015) A&A 577, A41. [10] Beck P. et al. (2014) Icarus 229, 263-277. [11] Aléon-Toppani A. et al. (2020) Lunar and Planetary Science Conference 2682. [12] Hamilton V. et al. (2019) Nat. Astron. 3, 332–340.

Frozen methanol was detected in the outer solar system on the surfaces of the Centaur 5145 Pholus, the Trans-Neptunian Object (55638) 2002 VE95, and more recently on (486958) Arrokoth. The icy surfaces of these objects are subjected to solar and cosmic ions that modify the physico-chemical properties of their surface. To study the effects of ion bombardment on methanol-rich surfaces, we performed experiments of ion irradiation of H2O:CH3OH mixtures and we monitored the evolution of the methanol near-infrared bands. We observed significant variations of the 2.34/2.27 μm methanol band ratios as a function of the irradiation dose. We then used the Arrokoth and Pholus spectra to test the 2.34/2.27 μm band ratio as a probe of irradiation of methanol-rich surfaces, and we estimated the timescales of processing by solar and cosmic ions. Our results indicate that solar energetic particles are the main drivers of changes in the near-infrared spectra of frozen surfaces in the outer solar system.

Primitive extraterrestrial materials are generally dark, a characteristic often associated with the presence of polyaromatic organic material and/or sulfides. We show in this study that the reflectance level measured at 0.55 μm of IDPs and some meteorites is correlated to the degree of graphitization of the polyaromatic organic matter. The reflectance level of the primitive surfaces therefore allows us to obtain information on the polyaromatic organic material present on the surface of solar system small bodies observed by remote sensing or visited by space missions. We discuss our results in view of the sample return missions Hayabusa2 and OSIRIS-REx.

International audience

Space weathering produces variations in the optical properties of small solar system body surfaces. Laboratory studies have been performed by several groups on different meteorite classes, aimed at simulating space weathering by using ion irradiation and laser ablation. Here we present new FTIR spectral imaging data of ion irradiated carbonaceous chondrites (CV Allende and CM Murchison meteorites), simulating solar wind irradiation on primitive asteroids. Irradiation conditions (40 keV He+ and Ar+ up to 3.1016 ion/cm2) were reported in detail in previous studies. The new analyses were performed with a FTIR micro-spectrometer equipped with an FPA (Focal Plane Array) detector. Micro-reflectance spectra were acquired in the 2.5–12 μm range using a spot size of 20 μm and scanning large areas (from mm2 to cm2) of the meteorite pellets, both on virgin areas and on areas irradiated with different doses. Spectral maps allow us characterizing the heterogeneity of the meteorites at the 20 μm spatial scale. In the irradiated areas, we observe spectral modifications of both anhydrous and hydrated silicates. Spectral shifts are observed after irradiation, larger for anhydrous than hydrated silicates. Compositional heterogeneity of the pristine materials and irradiation effects are compared to each other as a function of the irradiation dose, to determine which spectral features are more sensitive to space weathering. Results are then compared with the IR spectral capabilities of instruments onboard the Hayabusa2/JAXA and OSIRIS-REx/NASA spacecrafts, to provide these missions with spectral criteria on how to distinguish space weathering from compositional heterogeneity effects at the asteroid, and in view of surface selection for sample return.

We present the analyses results of two bulk Terminal Particles, C2112,7,171,0,0 and C2112,9,171,0,0, derived from the Jupiter-family comet 81P/Wild 2 returned by the Stardust mission. Each particle embedded in a slab of silica aerogel was pressed in a diamond cell. This preparation, as expected, made it difficult to identify the minerals and organic materials present in these particles. This problem was overcome using a combination of three different analytical techniques, viz. FE-SEM/EDS, IR, and Raman microspectroscopy that allowed identifying the minerals and small amounts of amorphous carbon present in both particles. TP2 and TP3 were dominated by Ca-free and low-Ca, Mg-rich, Mg,Fe-olivine. The presence of melilite in both particles is supported by IR microspectroscopy, but is not confirmed by Raman microspectroscopy, possibly because the amounts are too small to be detected. TP2 and TP3 show similar silicate mineral compositions, but Ni-free and low-Ni, subsulfur (Fe,Ni)S grains are present in TP2 only. TP2 contains indigenous amorphous carbon hot spots; no indigenous carbon was identified in TP3. These nonchondritic particles probably originated in a differentiated body. This work found an unanticipated carbon contamination following the FE-SEM/EDS analyses. It is suggested that organic materials in the embedding silica aerogel are irradiated during FE-SEM/EDS analyses creating a carbon gas that develops a strong fluorescence continuum. The combination of the selected analytical techniques can be used to characterize bulk Wild 2 particles without the need of extraction and removal of the encapsulating aerogel. This approach offers a relatively fast sample preparation procedure, but compressing the samples can cause spurious artifacts, viz. silica contamination. Because of the combination of techniques, we account for these artifacts.

International audience; Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been proposed as surface analogs for about two-thirds of all C-complex asteroids. However, this suggestion appears to beinconsistent with the presence of hydrated silicates on the surfaces of some of these asteroids, including Ceres. Here, we report the presence of enstatite (pyroxene) on the surface of two C-type asteroids (Ceres and Eugenia) based on their spectral properties in the mid-infrared range. The presence of this component is particularly unexpected in the case of Ceres, becausemost thermal evolution models predict a surface consisting of hydrated compounds only. The most plausible scenario is that Ceres' surface has been partially contaminated by exogenous enstatite-rich material, possibly coming from the Beagle asteroid family. This scenario questions a similar origin for Ceres and the remaining C-types, and it possibly supports recent results obtained by the Dawn mission (NASA) that Ceres may have formed in the very outer solar system. Concerning the smaller D∼200 km C-types such as Eugenia, both their derived surface composition (enstatite and amorphous silicates) and low density (

Aims. Olivine surfaces have been subjected to low-energy ion irradiation with H + ,H e + and Ar + at energies within the keV range in order to simulate the effects of energetic gas-grain interactions within shocked regions of the interstellar medium. Methods. The induced modifications in the chemical composition and the bonding configuration of the upper and the near surface regions were monitored in situ by X-ray photoelectron spectroscopy (XPS). The associated morphological evolution of the samples was studied by atomic force microscopy (AFM). Results. Results show that the surface chemistry evolves during irradiation with a noticeable Mg enrichment relative to Si. This evolution is interpreted as coming from magnesium atom diffusion driven by the electric field caused by the positive ion implantation. The iron valence state is also strongly affected by irradiation, with reduction occurring at relatively high fluxes. However, at low fluxes the iron is found to oxidise from Fe 2+ to Fe 3+ due to a charge transfer between the incident positive ions and the iron in the sample. The atomic force microscopy results show that the surface roughness tends to increase with irradiation and that this roughness influences the surface chemical reactivity of the grains, as shown by the enhanced formation of carbonate on the surfaces when they are exposed to a CO2 atmosphere. The implications for the evolution of interstellar dust include an enhanced dust catalytic activity. These effects would arise from modification under irradiation of the surface reactivity and an increase in the available grain surface area.

We report combined micro-infrared, micro-Raman, and field emission scanning electron microscope (FESEM) analyses of particles collected by the Stardust spacecraft during its flyby of comet 81P/Wild 2 on 2 January 2004 and successfully returned back to Earth on 15 January 2006. We present mid-infrared (IR) spectra of six of these particles. The CH2/CH3 ratios inferred from the infrared data are greater than those seen in organics in the diffuse interstellar medium, possibly indicating the presence of longer or less branched aliphatic chains. The micro-Raman data offer insights into the state of the order of the carbonaceous component present in the particles. Raman parameters for most of the particles span a similar range to that observed in interplanetary dust particles (IDPs) and the most primitive meteorites. Both the IR and Raman data imply the presence of a very labile carbonaceous component. Hydrated silicates may be present in two particles of Track 35, one of which may also contain carbonates, but further investigations with other techniques need to be performed to confirm these findings. In some cases, the analyses are difficult to interpret because of the presence of compressed aerogel mixed with the grains.

Context. We recently reported the formation of metallic inclusions in an amorphous and/or crystalline silicate matrix by thermal annealing of thin films in reducing atmospheres. Experimentally, the obtained microstructures closely resemble those of the glass with embedded metal and sulphides (GEMS) found in chondritic porous interplanetary dust particles (CP IDPs). We present here the magnetic properties of these synthetic samples. Aims. In this paper we report the detection and measurements of single domain and super paramagnetic ferromagnetic inclusions (SD/SP) in annealed silicate thin films of composition analogous to interstellar silicates and discuss the implications for the alignment of cosmic grains in astrophysical environments, in the presence of weak magnetic fields. Methods. We investigate the magnetic properties of synthesized laboratory silicate samples by measuring their magnetization when subjected to a given magnetic field. The measurements were performed at different temperatures including those compatible with interstellar dust. Results. The high values of remanent magnetization at saturation obtained in this work suggest the ability of our samples to indefinitely maintain a significant magnetization which may contribute to their alignment in weak magnetic fields. Conclusions. From our laboratory experimental simulation we propose that interstellar grains contain iron in form of nm-sized metallic beads. This can explain the non-detection of iron in interstellar grains. These inclusions could play a role in the alignment of grains. We propose a possible scenario for the magnetization of the cosmic grains and give a minimum value for the magnetic susceptibilty for GEMS.

International audience; Hayabusa‐returned samples offer a unique perspective for understanding the link between asteroids and cosmomaterials available in the laboratory, and provide insights on the early stages of surface space weathering. This study characterizes the mineralogy and the extent of space weathering of the three Itokawa particles RA‐QD02‐0163, RA‐QD02‐0174, and RA‐QD02‐0213 provided by JAXA to our consortium. We report here a series of results based on nondestructive analyses through visible‐near‐infrared reflectance and Raman spectroscopy. Results were obtained on the raw particles, both in their original containers and deposited on diamond windows. Identification of the minerals, characterization of their elemental compositions, and measurements of their relative abundances were led through Raman spectroscopy in punctual and automatic mode. Reflectance spectra in the visible and near‐IR wavelengths constrain the mineralogy of the grains and allow direct comparison with the surface of Itokawa. The spectra reflect the extent of space weathering experienced by the three particles. Particle RA‐QD02‐0163 consists of a heterogeneous mixture of minerals: olivine (Fo76) dominates an assemblage with both Ca‐rich (En50, Wo50) and Ca‐poor (En85) pyroxenes. The elemental compositions of the silicates are consistent with those previously reported for distinct Hayabusa particles. Particles RA‐QD‐0174 and RA‐QD02‐0213 are solely composed of olivine, whose chemical composition is similar to that observed in RA‐QD02‐0163. It has been previously shown that the S‐type asteroid 25143 Itokawa is a breccia of poorly equilibrated LL4 and highly equilibrated LL5 and LL6 materials. The three particles studied here can be related to the least metamorphosed lithology (LL4) based on the high forsterite content of the olivine. Neither carbonaceous matter nor hydrated minerals were detected through Raman on the three allocated particles. The NIR‐VIS reflectance (incidence = 45°, light collection at e = 0°) spectra of the three particles, in particular the 1 μm band, are consistent with the presence of both olivine and pyroxene detected via Raman. The spectra of particles RA‐QD02‐0163 and RA‐QD02‐0213 are also fully compatible with the ground‐based observations of asteroid (25143) Itokawa in terms of both spectral features and slope. By contrast, particle RA‐QD02‐0174 has a similar 1 μm band depth but higher (redder) spectral slope than the surface of Itokawa. This probably reveals a variable extent of space weathering among the regolith particles. RA‐QD02‐0174 may contain a higher amount of nanophase metallic iron and nanophase FeS. Such phases are products by space weathering induced by solar wind, previously detected on other Itokawa particles.

International audience; Meteorites have long been considered as reflections of the compositional diversity of main belt asteroids and consequently they have been used to decipher their origin, formation, and evolution. However, while some meteorites are known to sample the surfaces of metallic, rocky and hydrated asteroids (about one-third of the mass of the belt), the low-density icy asteroids (C-, P-, and D-types), representing the rest of the main belt, appear to be unsampled in our meteorite collections. Here we provide conclusive evidence that the surface compositions of these icy bodies are compatible with those of the most common extraterrestrial materials (by mass), namely anhydrous interplanetary dust particles (IDPs). Given that these particles are quite different from known meteorites, it follows that the composition of the asteroid belt consists largely of more friable material not well represented by the cohesive meteorites in our collections. In the light of our current understanding of the early dynamical evolution of the solar system, meteorites likely sample bodies formed in the inner region of the solar system (0.5-4AU) whereas chondritic porous IDPs sample bodies that formed in the outer region (\textgreater5 AU).

Various microscopic techniques were used to characterize experimental micro- craters in aluminium foils to prepare for the comprehensive analysis of the cometary and interstellar particle impacts in aluminium foils to be returned by the Stardust mission. First, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) were used to study the morphology of the impact craters and the bulk composition of the residues left by soda-lime glass impactors. A more detailed structural and compositional study of impactor remnants was then performed using TEM (Transmission Electron Microscopy), EDS, and electron diffraction methods. The TEM samples were prepared by Focused Ion Beam (FIB) methods. This technique proved to be especially valuable in studying impact crater residues and impact crater morphology. Finally, we also showed that InfraRed microscopy (IR) can be a quick and reliable tool for such investigations. The combination of all of these tools enables a complete microscopic characterization of the craters.

Using FTIR and Raman microspectroscopies we have analysed 6 fragments of the Tagish Lake meteorite. The data obtained show that all the fragments belong to the carbonate-rich lithology, where an organic material, including a highly disordered macromolecular carbonaceous component is found. The FTIR approach shows that part of the organic material present in Tagish Lake is aliphatic. The Raman approach shows that there is also highly disordered polyaromatic organic material, which is abundant. Furthermore, the comparison of Raman data of Tagish Lake to other carbonaceous chondrites (CI, CM2, CR2) shows that the carbon in Tagish Lake is different, supporting the assertion that this meteorite is a unique and new type of carbonaceous chondrite. The comparison of the aliphatic hydrocarbon FTIR data found in the Tagish Lake meteorite with the aliphatic hydrocarbon IR data of the carbonaceous chondrites Orgueil and Murchison and with the diffuse Interstellar Medium (ISM) shows that they are different, in that the Tagish Lake meteorite has longer aliphatic chains.

An original apparatus based on laser-induced fluorescence detection is presented. One lane migration combined to four equidistant detection points allows the study of the dynamics of DNA bands during electrophoresis. We focus this article on the study of the mobility of DNA sequencing fragments as a function of temperature; mobility is determined in 4% T, 5% C and 4.3% T, 5% C cross-linked polyacrylamide gels at an electric field of 45 V/cm [T=(g acrylamide+g N,N'-methylenebisacrylamide)/100 ml solution; C=g N,N'-methylenebisacrylamide/% T]. Activation energy has been investigated under these experimental conditions with a temperature varying from 25 to 50 degrees C. The activation energy for migration through the cross-linked polyacrylamide gel decreases with fragment length under our experimental conditions and it varies along the migration.

Interplanetary Dust Particles (IDPs) are potentially of cometary origin. They may therefore provide important clues to a better understanding of the early Solar System physical and chemical conditions. A chondritic porous aggregate IDP (named L2021C5) was analyzed using mid to far FTIR (2–60 μm) micro-spectroscopy, Raman micro-spectroscopy, field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analyses. The IDP was pressed between diamond windows to increase the quality of the spectral data by overcoming the diffraction limitation and minimizing light scattering effects from particles of a global size similar to the wavelength of the observation. This combination of techniques has enabled a mineralogical, organic and compositional description of the compressed particle. The IR spectra show that in L2021C5 amorphous silicates are more abundant than crystalline ones, and that the crystalline component is richer in olivine than in pyroxene. The composition and distribution of these inorganic components match very well the small silicate grains emission observed for comet Hale-Bopp from ISO-SWS spectra. Raman spectroscopy has allowed the detection of carbonaceous structures displaying different degrees of order, covering almost the whole range observed so far for IDPs. The combination of the three analytical techniques indicates that L2021C5 is a low-Ca, chondritic porous aggregate that experienced only mild flash heating on atmospheric entry, as indicated by the disordered carbon properties, the Fe/S atomic ratio of sulfides, the absence of Na depletion, and the small depletion of S. Based on a plausible cometary origin and on the estimated low entry velocity, we suggest that this IDP came from the Zodiacal cloud that is dominated by dust from Jupiter-Family comets.

Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.

Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.

We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed (∼180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

We have examined some grains from the Paris meteorite through infrared and Raman micro-spectroscopy in order to investigate their carbonaceous and mineralogical components. In the mid- as well as far-infrared regions, the raw and global spectra of Paris resemble those of CM meteorites. However, we have obtained rather peculiar infrared spectra for some aromatic-rich micron-sized fragments of Paris displaying a very good match between its organic signatures both in the 3.4 ?m and 6 ?m regions, and the ones observed from the diffuse interstellar medium infrared sources toward the Galactic center, suggesting that this meteorite may have indeed preserved some organic matter of interstellar origin.

International audience; Context. Interstellar silicate grains are thought to be amorphized by interaction with high- and low-energy particle interactions in astrophysical environments. In addition, low energy (a few keV) particles will implant atoms within the grains.Aims. In this paper we experimentally investigate the consequence of the implantation of H+ at low irradiation energies into analogues of interstellar silicate grains, and look for the formation of hydroxyl radicals within the silicate matrix.Methods. Thin amorphous silicate films (~100 nm) were sequentially irradiated with H+ ions at low energies (3.5, 2.5 and then 1.5 keV) ensuring an implantation of the ions through the full depth of the films. The fluences used, 3 × 1016, 1017 and 3 × 1017 H+/cm2, are compatible with those expected in shocks in the interstellar medium. We used infrared spectroscopy to monitor and quantify the OH band evolution after irradiation. In order to distinguish the newly formed OH groups from those originating from unavoidable atmospheric contamination, the D/H depth ratios were measured with a NanoSIMS ion microprobe.Results. An increase in the OH band strength in the infrared spectra after irradiation reveals the formation of OH bonds within the irradiated silicate thin films. NanoSIMS measurements of the D/H signature in the region of ion implantation show that the newly-formed OH groups make up about 40% of the observed OH band in the IR, the rest are due to an atmospheric hydroxylation of the sample. Only about 2% of the incident ions lead to OH bond formation and, at most, the irradiated silicates retain about 3% of the incident protons as OH groups within their structure.Conclusions. Our laboratory experimental simulations show a possible production and storage of hydroxyl radicals in amorphous laboratory silicates. In the astrophysical context, such OH radicals, strongly bonded to pre-accretion material, could constitute a non negligible reservoir of -OH, thus water. These experimental results allow us to revisit and reinstate the hypothesis of a possible “wet” accretion of the telluric planets early in the history of the formation of the Solar System.

Particles emanating from comet 81P/Wild 2 collided with the Stardust spacecraft at 6.1 kilometers per second, producing hypervelocity impact features on the collector surfaces that were returned to Earth. The morphologies of these surprisingly diverse features were created by particles varying from dense mineral grains to loosely bound, polymineralic aggregates ranging from tens of nanometers to hundreds of micrometers in size. The cumulative size distribution of Wild 2 dust is shallower than that of comet Halley, yet steeper than that of comet Grigg-Skjellerup.

Laboratory analyses performed on extraterrestrial materials originating from primitive bodies of our Solar System, that are bodies known to have suffered low alteration since their formation 4.6 billion years ago, can improve our knowledge on processes that have occurred in the early phase of our planetary system. Furthermore, laboratory simulations of some processes that these materials are likely to suffer during their life cycle also bring precious indications for interpreting observational data as well as for understanding the evolution of solids from the Interstellar Medium to their incorporation into planetary bodies, these latter including asteroids, comets and all kinds of dust that may be observed and/or collected back to Earth.During this thesis, the analysis of silicate as well as organic materials, which have not been much studied jointly so far, in stratospheric particles of cosmic origin, reveals a correlation between the mineralogy of the grains and the lengths of the chains of their carbonaceous component. This link does not seem to be due to parent body processing but rather to trace pre-accretionnal processes. The preservation of pristine components in extraterrestrial materials slightly altered on their parent bodies is again confirmed by the discovery in this work, of inclusions in the “Paris” carbonaceous chondrite whose infrared spectra are similar to the interstellar carbonaceous species. The study of cometary grains from the Stardust space mission showed, unlike the common idea that comets should be composed only of primitive materials since they reside in a cold reservoir, that comets do also contain a number of materials formed at high temperature, thus confirming results from previous studies of Stardust samples and implying large-scale radial mixing of materials in the young Solar system disk.The second part of my work, dedicated to experiments on primitive extraterrestrial amorphous silicates analogs, is aimed to study the role that materials from which Earth has accreted could have played in its water budget in the frame of the “wet accretion” scenario. The experiments performed along this thesis simulating interactions between silicates and water vapor, showed that silicates allow the storage of large quantities of water by adsorption onto their surface of molecules directly from the gas phase.; L’étude en laboratoire de matériaux extraterrestres provenant d’objets ayant peu ou pas évolué depuis leur formation il y a environ 4.6 milliards d’années, peut améliorer notre connaissance sur les débuts de notre système planétaire. Par ailleurs, la simulation en laboratoire de certains processus que ces matériaux sont susceptibles de subir au cours de leur histoire apporte également de précieuses informations pour l’interprétation des données issues des observations astronomiques ainsi que pour la compréhension de l’évolution des solides du Milieu Interstellaire jusqu’à leur incorporation dans des objets planétaires, objets incluant aussi toutes sortes de débris tels que les astéroÏdes, les comètes et toutes sortes de poussières accessibles à la collecte et/ou à l’observation.Au cours de cette thèse, l’analyse des matériaux organiques ainsi que des matériaux silicatés, jusqu’alors peu étudiés conjointement, dans les poussières stratosphériques d’origine cosmique, révèle une corrélation entre la minéralogie des grains et la longueur des chaînes carbonées. Ce lien ne semble pas le fruit de processus à la surface des corps parents des grains mais semble plutôt tracer des processus pré-accrétionnels. La conservation de composants peu altérés sur les corps parents dans les matériaux extraterrestres est encore une fois confirmée par la découverte, au cours de cette thèse, d’inclusions dans la météorite carbonée « Paris » dont les spectres infrarouges sont très similaires à ceux des composés carbonés observés dans le Milieu Interstellaire. L’étude de grains cométaires issus de la mission spatiale Stardust a montré, contrairement à l’idée que les comètes soient composées uniquement de matériaux primitifs puisque conservés dans un réservoir froid, que celles-ci contiennent aussi un certain nombre de matériaux formés à haute température, confirmant alors de précédentes analyses d’échantillons de Stardust et impliquant des échanges de matériaux à grande échelle radiale dans le jeune Système solaire.La deuxième partie de ce travail, consacrée à l’étude d’analogues de matière extraterrestre, porte sur le rôle qu’ont pu jouer les matériaux à partir desquels les planètes telluriques se sont formées dans l’apport de l’eau sur la Terre dans le cadre du scénario dit de « wet accretion ». Les expériences effectuées au cours de cette thèse visant à simuler les interactions entre silicates et vapeur d’eau ont montré que ces matériaux permettent de stocker d’importantes quantités d’eau à leur surface par adsorption des molécules de la phase gazeuse.