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Introduction: Hayabusa2 spacecraft returned samples from near-Earth C-type asteroid 162173 Ryugu to the Earth on 6 Dec. 2020 [1]. Since the samples had been returned, we continue describing individual Ryugu particles for their images, weights, visible and infrared spectra with an optical microscope, a balance, a monochronic digital microscope with six-bands filters for incident light, an FT-IR and the infrared microscope MicrOmega [1, 2]. So far, 404 individual Ryugu particles have been handpicked and described for all or some of the methods [3-11].

Overview of initial descriptions of individual Ryugu particles:  As mentioned in [3, 4], individual Ryugu particles have been grouped into angular or rounded in their shapes and smooth and rough in their mor-prologues. In total, those having rounded-shape (59%) and rough-surface (80%) are dominant in them. The relationship with their optical morphologies and surface mineralogizes were confirmed for the four individual Ryugu particles with an electron microscope [12], indicating those showing smooth surfaces showing space-weathering features on their surfaces. Although it is still poor in statistics, surface morphologies might reflect their mineralogical fea-ture such as space weathering. More samples should be investigated for better statistics to understand relationship between morphologies and space weathering. Among 404 individual Ryugu particles, 244 of them have been analyzed for their infrared reflectance spectra with the FT-IR. 2.7µm absorption, corresponding to presence of -OH, have been detected from all of them, indicating ubiquitous presence of hydrous minerals in Ryugu samples. 3.4 µm absorption features, corresponding to presence of carbonate and/or -CH, have been detected from 48% of them. As pointed before [3], this should be partially due to their heterogeneous distribution of carbonate and/or organic components in them, and that the spectral feature in 3.4 µm is much weaker than 2.7 µm so that it cannot be detected by the FT-IR.  The MicrOmega will help to detect minor spectral features from such small particles, even though there is limitation of number of analyses per day (2 individual particles per day). Visible spectra of individual Ryugu samples have been also analyzed with the digital microscope of muti-band filters [7]. The average spectrum of 69 individual Ryugu particles are comparable to that of bulk Ryugu samples, indicating there is no spectrally different particle among them.  Due to the schedule of analyses, not all of the individual Ryugu particles have been analyzed for the visible spectra, but we should proceed the analysis to understand overall spectral features of Ryugu samples.

Ryugu sample database and announcement of opportunity (AO) for Ryugu samples: All the obtained initial description data shown above is open in public by the Ryugu Sample Database System (https://darts.isas.jaxa.jp/curation/hayabusa2/) [13]. The first AO is ongoing based on this database, and the samples will be distributed to principal investigators of selected research proposals from this June (see detail in https://jaxa-ryugu-sample-ao.net/). Additionally, the second AO is planned to be released in this summer.

References: [1] Yada T. et al. (2021) Nature Astron. 6: 214. [2] Pilorget C. et al. (2021) Nature Astron. 6: 221. [3] Yada T. et al. (2022) LPS LIII, Abstract #1831. [4] Miyazaki A. et al.  (2022) LPS LIII, Abstract #1816. [5] Hatakeda K. et al. (2022) LPS LIII, Abstract #1828. [6] Yogata K. et al. (2022) LPS LIII, Abstract #1767. [7] Yumoto K. et al. (2022) LPS LIII, Abstract #1326. [8] Yabe Y. et al. (2022) LPS LIII, Abstract #2371. [9] Pilorget C. et al. (2022) LPS LIII, Abstract #2088. [10] Carter J. et al. (2022) LPS LIII, Abstract #2017. [11] Loizeau D. et al. (2022) LPS LIII, Abstract #1495. [12] Nakato A. et al. (2022) LPS LIII, Abstract #1810. [13] Nishimura M. et al. (2022) LPS LIII, Abstract #1731.

How to cite: Yada, T., Abe, M., Yogata, K., Miyazaki, A., Hatakeda, K., Hitomi, Y., Sugiyama, Y., Nishimura, M., Sakamoto, K., Kanemaru, R., Kumagai, K., Soejima, H., Nakato, A., Okada, T., Fukai, R., Sugahara, H., Ishizaki, T., Suzuki, S., Tachibana, S., and Usui, T. and the ONC-T team and IAS team: Present status of initial descriptions and distributions of Ryugu samples returned by Hayabusa2, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1100, https://doi.org/10.5194/epsc2022-1100, 2022.

Introduction:  On December 6, 2020, the Hayabusa2 mission successfully returned to Earth ~ 5.4 g of samples collected at the surface of the C-type asteroid Ryugu [1,2]. Its surface was first sampled on February 22, 2019 ("bulk A"), then on July 11, 2019, close to a 15-meter large artificial crater, so as to possibly access sub-surface material ("bulk C") [3]. The collected samples are now kept at the JAXA Extraterrestrial Curation Center in ISAS (Institute of Space and Astronautical Science) for a first round of preliminary analyses, with the objective of characterizing in a non-destructive manner both the bulk samples and a few hundreds of grains extracted from them [4]. In particular, the goals were 1) to support their further detailed characterization by the international Initial Analysis Teams, and 2) to build a catalogue of the grains, accessible to the international community through AO selection, starting mid-2022. Importantly, the analyzed samples have always been kept, since their collection, in a fully clean and controlled environment either under vacuum or ultra-clean N₂. The analyses performed within the curation facility provided an unexpected set of important results. 

Methods:  The preliminary characterization of these samples is being conducted with a visible microscope equipped with six color filters [4], a FTIR spectrometer (1-4 µm) [4], and MicrOmega, a hyperspectral microscope [5], operating in the near-infrared range (0.99-3.65 µm) where diagnostic signatures of most candidate minerals and molecules of relevance (e.g. mafic minerals, altered phases, salts, ices, aliphatic/aromatic CH, NH-rich compounds) can be found. For each 22.5×22.5 µm² pixel of the 250×256 pixels² field of view, the reflectance spectrum is retrieved in up to 400 contiguous spectral channels. Both the negligible amount of illuminating power at less than 10^-8 W/px and the lack of contact with the samples allow entirely non-destructive and non-invasive characterization. By the beginning of 2022, bulk samples from chamber A and chamber C of the Hayabusa2 returned capsule (each divided into 3 sub-bulks), as well as >200 individual grains and 14 “small-bulks” extracted from them have been analyzed with MicrOmega.

Figure 1.  Example of carbonate detections highlighting carbonates as red pixels. Left: MicrOmega images with A: extracted grain C0041. B: bulk samples from chamber A. C: bulk samples from chamber C. Right: Average spectra of pixels with carbonate detections within the colored boxes in the left images.

Results: When analyzed at the mm-scale by averaging thousands of pixels, the spectra of bulk A and bulk C exhibit a pattern similar to those acquired remotely down to the meter scale by the NIR spectrometer NIRS3 on board Hayabusa2 [6]. The global reflectance is extremely low, 2-3 %, in agreement with the measurements of the ONCs (Optical Navigation Cameras) and NIRS3 at Ryugu [7,8], and consistent with the taxonomic spectral classification of Ryugu as a C-type asteroid [1,2]. The main spectral feature is the diagnostic OH absorption centered at 2.715 +/- 0.005 µm, position compatible with that of NIRS3 spectra [8,9]. MicrOmega spectra also exhibit a broad feature in the 3.3-3.5 µm range, centered around 3.4 µm, present throughout the sub-bulk samples. This feature is considered indicative of the large-scale presence of a variety of CH- rich compounds and carbonates. A fainter ~3.1 µm broad feature, indicative of the presence of NH-bearing compounds is also detected, although with varying and much fainter intensities. At a sub-millimeter scale, however, heterogeneities do clearly show up, either or both at grain level or as inclusions within grains. Detections include for example: 1) carbonates of various compositions, detected on a rather large number of occurrences with sizes ranging from a few tens to a few hundreds of micrometers (see a few examples Fig. 1) ; 2) spots enriched in organics, in particular through a 3.4 µm feature indicative of the presence of aliphatic compounds (see one example Fig. 2) ; 3) spots enriched in a nitrogen-rich phase, through a ~3.1 µm feature sometimes coupled to additional spectral features. These detections, as well as others, will be presented and candidates will be discussed. Noticeably, no chondrules nor refractory inclusions have been identified so far.

Figure 2. CH-rich spectrum on a localized spot within bulk A (a) compared to a typical spectrum of a carbonate rich spot (b),emphasizing the diagnostic difference of the “3.4 µm” feature. Both spectra are 3×3 pixels average spectra. Dashed lines are set at 3.32 µm, 3.41 µm and 3.455 µm to highlight the differences in band position and shape [6].

Conclusion: The initial spectral characterization of the returned samples by MicrOmega currently points towards Ryugu containing a fascinating variety of grains, including OH-, CH- and NH-rich compounds spread at a global scale, and alteration products, among which highly diagnostic carbonates in a variety of cation contents. The occurrence of volatile-rich species, likely originating from the outer solar system, would support Ryugu having preserved some of its pristine constituents, together with their partially altered phases. The Hayabusa2 returned samples, thus, appear among the most primordial material available in our laboratories.

References: [1] Binzel R. P. et al. (2002), Physical Properties of Near-Earth Objects. pp. 255-271, [2] Vilas F. (2008) The Astronomical Journal 135 (4), 1101-1105, [3] Morota et al. (2020) Science 368, Issue 6491, pp. 654-659, [4] Yada, T., et al., Nature Astronomy, 2021, Volume 6, p. 214-220, [5] Bibring J.-P. et al. (2017) Astrobiology 17, Issue 6-7, pp.621-626, [6] Pilorget, C., et al., Nature Astronomy, 2021, Volume 6, p. 221-225, [7] Sugita S. et al. (2019) Science 364 (6437), 252-252, [8] Kitazato K. et al. (2019) Science 364 (6437), 272-275, [9] Kitazato K. et al. (2020) Nature Astronomy, Volume 5, p. 246-250.

How to cite: Loizeau, D., Pilorget, C., Bibring, J.-P., Okada, T., Brunetto, R., Yada, T., Riu, L., Usui, T., Hatakeda, K., Nakato, A., Yogata, K., Abe, M., Aleon-Toppani, A., Baklouti, D., Carter, J., Langevin, Y., Lantz, C., and Le Pivert-Jolivet, T. and the MicrOmega Hayabusa 2 Curation Team: NIR Hyperspectral Imaging of Hayabusa 2 Returned Samples by the MicrOmega Microscope within the ISAS Curation Facility, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-898, https://doi.org/10.5194/epsc2022-898, 2022.

Introduction:  JAXA’s Hayabusa2 asteroid sample return mission targeted the carbonaceous (C-type) asteroid 162173 Ryugu. The Hayabusa2 spacecraft collected samples from two touchdown sites on Ryugu and returned them to Earth on December 6, 2020, six years after launch. Since then, the goal of the Insoluble Organic Macromolecule Initial Analysis Team (PI: H. Yabuta) has been to elucidate the distributions and chemical characteristics of macromolecular organic materials in a C-type asteroid [1]. The degree of structural order of the polyaromatic carbonaceous matter present in extraterrestrial samples is a tracer of the thermal history they experienced (e.g., primitive chondrites: [2-5]; micrometeorites: [6-7]). To characterize Ryugu’s thermal history (long vs. short thermal heating and its extent), we thus perform Raman characterization of several intact grains and also on extracted insoluble organic matter from aggregates originating from the two collecting sites. In order to be fully confident in the obtained data and interpretation, Raman characterization was led independently by two groups in Japan and in France on distinct Ryugu particles.

Samples and methods:  Raman point analyses were performed on several fragments of several intact grains from Chamber A aggregates (A0108, A0106) from the first touchdown site and six intact grains from Chamber C aggregates (C0109, C0057) from the second touchdown site. The insoluble carbonaceous residue isolated by acid treatment from the same aggregates have also been characterized and the data are currently being interpreted.

The Raman spectra were acquired with a 532 nm laser in both Japan and France. Because some Raman bands related to carbonaceous matter are dispersive, data for Ryugu particles and comparison samples have been acquired and analyzed consistently in both Japan and in France. In particular, in France, Raman measurements were performed at the Ecole Normale Supérieure de Lyon (Laboratoire de Géologie de Lyon—Terre, Planètes, Environnement) using a LabRam HR800 Raman spectrometer (Horiba Jobin-Yvon) equipped with a 600 g/mm grating. The laser was focused through a 100× objective to obtain a <2 μm spot size. The power on the sample was 0.3 mW. Each acquisition comprised six integrations of 15 s that were averaged to make the final spectrum.

Results and Discussion:  The Raman data acquired in Japan and in France are fully consistent. Each acquired spectrum is characterized by a high fluorescence background and by the presence of the Raman D- (~ 1350 cm^-1) and G-bands (~ 1580 cm^-1), related to the presence of poorly ordered carbonaceous matter. The spectral parameters derived from the mathematical fitting of the individual spectra - band widths (FWHM_D, FWHM_G), band positions (ω_D, ω_G), and band intensity ratio (I_D/I_G) - are all clustering in the same area (Fig. 1).  

In order to evaluate the thermal history of the Ryugu asteroid, the spectral parameters derived from Ryugu’s samples were compared with those obtained on meteorites. In a plot FWHM_Gvs. ω_G (Fig. 1B), the Ryugu samples are clearly distinct from petrologic type 3 chondrites. In the plots FWHM_Dvs. I_D/I_G (Fig. 1C) and ω_Gvs. ω_D (Fig. 1D), the parameters from Ryugu samples are comparable to those derived from the primitive Ivuna-type (CI) and Mighei-type (CM) carbonaceous chondrites of petrologic types 1 and 2, respectively. On the other hand, they are distinct from thermally metamorphosed CM chondrites, such as Wisconsin Range (WIS) 91600, Pecora Escarpment (PCA) 02012, and Jbilet Winselwan meteorites.

The interpretation of spectral data acquired on IOM is currently under progress. The spectral parameters are consistent with those derived from IOM extracted from primitive chondrites, as expected from the data obtained on intact particles.

These results indicate that Ryugu escaped significant long duration radiogenic thermal metamorphism as well as significant impact induced short-duration heating. This is consistent with tracers visible on IR spectra of the intact particles: presence of Mg-rich phyllosilicates and CH₂/CH₃ ratios comparable with primitive chondrites [8].

Acknowledgments: L.B. and E.Q. thank the French space agency CNES for its support.

References: [1] Yabuta et al. Submitted to Science – in revision [2] Bonal L. et al. (2006) GCA, 70, 1849-1863. [3] Bonal L. et al. (2016) GCA, 189, 312-337. [4] Busemann H. et al. (2007) Meteoritics & Planet. Sci. 42: 1387-1417. [5] Quirico E. et al. (2018) GCA, 241, 17-37. [6] Dobrica E. et al. (2011) Meteoritics & Planet. Sci. 46, 1363-1375. [7] Battandier M. et al. (2018) Icarus, 306, 74-93. [8] Kebukawa et al. (2022) LPSC abstract #1271.

How to cite: Bonal, L., Quirico, E., Montagnac, G., Komatsu, M., and Yabuta, H. and the The Hayabusa2-initial-analysis IOM team: Thermal history of Ryugu based on Raman and IR characterization of Hayabusa2 samples, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1131, https://doi.org/10.5194/epsc2022-1131, 2022.

Introduction: Primitive asteroids that accreted beyond the snowline in the protoplanetary disk likely played a crucial role in the delivery of water and organic matter to Earth and other terrestrial planets. The surface of the Cb-type asteroid 162173 Ryugu has low overall reflectance and an absorption feature at ~2.7 µm consistent with the presence of carbonaceous materials and phyllosilicates [1]. The spectral characteristics of Ryugu’s surface are most similar to the highly altered CI (“Ivuna-like”) and/or dehydrated CY (“Yamato-like”) carbonaceous chondrites [2].

In December 2020, JAXA’s Hayabusa2 mission successfully returned to Earth with >5 g of sample collected from the surface of Ryugu. The initial investigation of the samples suggested a close affinity with the CI chondrites [3], which consist of abundant phyllosilicates (~80 vol.%), plus minor amounts of magnetite (~10 vol.%), and dolomite (<5 vol.%), having experienced low temperature (<100°C) aqueous alteration [4]. In contrast, the CY chondrites contain dehydrated phyllosilicates and/or recrystallized olivine (~70 vol.%), Fe-sulphides (up to ~20 vol.%), and sometimes metal (~1 vol.%) following post-hydration metamorphism at temperatures >500°C [5]. Here, as part of the Hayabusa2 “Stone” preliminary examination team, we have characterised the modal mineralogy of a Ryugu particle to further constrain its aqueous and thermal history.

Methods: A powdered sub-sample of Ryugu particle C0002 (plates 3 and 4) was analysed using position-sensitive-detector X-ray diffraction (PSD-XRD) at the Natural History Museum (NHM), London. XRD patterns were acquired from the Ryugu powder using a high-intensity micro X-ray source for 6 hours, with the sample rotated throughout the analysis. Pure standards of each phase detected in the Ryugu powder were analysed under exactly the same conditions for 15 minutes. The modal mineralogy of the Ryugu powder was then determined using an established peak fitting method [4, 5].

Results & Discussion: Ryugu particle C0002 (plates 3 and 4) contains a mixture of Mg-rich serpentines and smectites that are present at an abundance of ~84 (± 2) vol.%. Other phases identified from the XRD pattern include magnetite (~8 vol.%), pyrrhotite (~7 vol.%), and dolomite (~2 vol.%). This mineralogy is broadly consistent with our petrographic observations of polished Ryugu sections (C0025-01 and C0103-02). Diffraction peaks from anhydrous olivine and pyroxene were not observed suggesting that their abundance is ≤1 vol.% in the analysed fraction of C0002. If we assume a maximum anhydrous silicate abundance of 2 vol.%, then the phyllosilicate fraction (PSF = total phyllosilicate abundance / [total anhydrous silicate + total phyllosilicate abundance]) of the Ryugu powder is 0.98, which corresponds to a petrologic sub-type of 1.1 on the alteration scale of Howard et al. [6].

The XRD pattern and modal mineralogy of Ryugu particle C0002 (plates 3 and 4) is very similar to the CI chondrites [4]. However, the Ryugu powder does not contain sulphates and ferrihydrite, which are common in the CI chondrites and thought to be terrestrial weathering products [7]. The Ryugu powder also has a comparable mineralogy to the recent C2_ung fall Tarda, which appears to be related to the Tagish Lake (C2_ung) meteorite [8]. However, Tarda retains partially altered chondrules and has a relatively high abundance of anhydrous silicates (~10 vol.%) [9]. In addition, the XRD pattern and modal mineralogy of the Ryugu powder is clearly distinct from the CY chondrites, which contain dehydrated phyllosilicates that lack coherent diffraction, and abundant poorly crystalline troilite and secondary olivine [5].

The modal mineralogy of Ryugu particle C0002 (plates 3 and 4) is consistent with having formed through low temperature aqueous alteration. The fluid-rock reactions reached near-completion, resulting in a secondary assemblage of phyllosilicate, sulphide, magnetite, and Mg-carbonate that was not overprinted by a later episode of thermal metamorphism at temperatures >~400°C.

References: [1] Kitazato et al. (2019) Science. 364:272. [2] Kitazato et al. (2021) Nature Astronomy. 5:246. [3] Yada et al. (2022) Nature Astronomy. 6:214. [4] King et al. (2015) Geochimica et Cosmochimica Acta. 165:148. [5] King et al. (2019) Geochemistry. 79:125531. [6] Howard et al. (2015) Geochimica et Cosmochimica Acta. 149:206. [7] Gounelle & Zolensky (2001) Meteoritics & Planetary Science. 36:1321. [8] Marrocchi et al. (2021) The Astrophysical Journal Letters 913:L9. [9] King et al. (2021) 52^nd LPSC, abstract #1909.

How to cite: King, A., Russell, S., Nakamura, T., Yurimoto, H., Noguchi, T., Okazaki, R., Yabuta, H., Naraoka, H., Sakamoto, K., Tachibana, S., Watanabe, S., and Tsuda, Y.: The modal mineralogy of asteroid 162173 Ryugu and its relationship to carbonaceous chondrite meteorites, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1264, https://doi.org/10.5194/epsc2022-1264, 2022.

1. Introduction

Hayabusa2 – Japanese Aerospace Exploration Agency Mission investigated the asteroid (162173) Ryugu and on 06 December 2020 successfully returned to the Earth ~5.4 g of collected materials. Indeed, the first touch-down operation (TD1) sampled surface material on  21st February 2019;  after the formation of a 15 m artificial crater with the SCI operation (Saiki et al., 2013), the TD2 occurred on 11st July 2019 and collected samples in the vicinity of crater, probably also subsurface material excavated by the impact. Ryugu appears to be a rubble-pile asteroid due to the low density (about 1.2 g/cm3) which suggests a formation by re-accumulation of fragments generated by the catastrophic destruction of the parent body (Watanabe et al., 2019). NIRS3 spectra of Ryugu surface acquired during Hayabusa2 mission show a strong features at 2.7 μm (indicating a OH-rich content ascribed to Mg-rich phyllosilicates) (Kitazato et al., 2019) and a secondary absorption at about 2.8 μm, strongly correlated with the 2.7 μm band (Galiano et al., 2020).

This work includes the Carbonaceous Chondrite meteorites (CCs) identification and selection in grains from ~1 to 4mm to simulate the Ryugu surface and analogue mixtures production by using different end-members: a dark component (graphite, carbon, etc.), Mg-rich phyllosilicates (i.e. Antigorite for OH stretching band at 2.7 μm) and Fe-rich dark component (e.g. Cronstedtite) to reproduce the 0.7 and 2.8 μm bands of Fe-bearing phyllosilicates. Four analogue mixtures have been sieved in the grain size 100-200 μm and 200-300 μm and named: Mixture#3, Mixture#4, Mixture#5 and Mixture#6. The spectra of the samples have been acquired by means of Bruker Vertex 80 FT-IR Spectrometer (incidence angle of 30° and emission angle of 0°) in the spectral range 2-4 μm (spectral resolution of 4 cm-1) and then compared with average Ryugu spectrum. The spectral slope (in the 2.0-2.5 μm range), Band Depth and Band Center of the feature at 2.7μm and reflectance at 2.1μm have been analysed.       

2. CCs meteorites analysis

The acquired meteorites spectra (fragments) compared with Ryugu ones are reported in Figure 1. The results show as the reflectance (at 2.1μm) values of meteorites (0.042 Murray, 0.032 Nagoya and 0.030 Nagoya) can be comparable with Ryugu reflectance level, i.e. 0.0296 as well as the BC (2.731 Murray, 2.749 Nagoya and 2.716 Nagoya and 2.719 of Ryugu spectra). Differently, the meteorites BD is from four to eight times more intense than Ryugu one.

Figure 1. Meteorites spectra and comparison with Ryugu (smoothed with 61 channels).

3. Analogue mixtures analysis

The analogue mixtures (about 0.1g) have been produced by considering the grain size of 100-200 µm and 200-300 µm (Figure 2). Each end-member has been analysed in the spectral range of interest, for example the Antigorite shows the bands at 2.3 µm (due to combination of Mg-O-H bending and O-H stretching) and at 2.7 µm (O-H stretching).  

Figure 2. Percentage composition of Ryugu analogue mixtures.

The Figure 3 at left shows the spectra of Mixture #3 and #4 while at right the Mixture #5 and #6 compared with the mean spectrum of Ryugu (obtained by NIRS3 data) multiplied by 7 for a better comparison. The Mixture#3 does not show the contribution of OH bands due to high percentage of dark component, i.e. 42.5%. Thus, the Mixture#4 has been produced by increasing the Mg-rich phyllosilicates, reducing the dark component  and introduce the Cronstedtite (Fe- bearing phyllosilicate). So that, it is important to introduce an additional dark component, i.e. the Cronstedtite (Fe- bearing phyllosilicate) which can help to decrease the reflectance level and to contribute to shallow  2.7 µm band due to OH.

Figure 3. Analogue mixtures compared with average Ryugu spectrum.

4. Preliminary results and future aims

The mixtures #4, #5, #6 showed a negative spectral slope due to the high percentage of Antigorite (up to 60%) responsible of the 2.7 μm band while 3 μm spectral band has been ascribed to the adsorbed atmospheric water. Furthermore, the Cronstedtite included in the Mixture#6 gave a contribution to the dark component equal to 32.5% by avoiding negative effects on 2.7 μm spectral band that remains to be well defined. Preliminary analysis exhibit a good comparison between Ryugu BC and analogue mixtures BC (due to the presence of Mg-phyllosilicate) whereas the BD in spectra of analogue mixtures is deeper than the Ryugu one. The Ryugu reflectance is two-three times lower than the mixtures reflectance and characterized by a positive spectral slope, contrarily to the mixtures’ spectra which have a negative spectral slope. Starting from Mixture#6, next step will aim at reducing the reflectance level and decrease the OH band contribution, as well as producing a positive spectral slope. By using thermal controlled setup in vacuum chamber at different temperatures (e.g. 100, 200, 300, 400°C), a thermal metamorphism can be simulated and new spectra will be acquired. In the future, laser and ion irradiations can be considered to simulate the micrometeorite impacts and solar wind processes which help to decrease the spectral level and increase the spectral slope, as well as  to reduce the analogue mixtures spectral bands. 

References: Galiano A., et. al. 2020, Icarus, v. 351, 113959; Kitazato, K. et al. 2019, Science 364, 6437: 272-275; Saiki, T., et al. 2013, Acta Astronautica, v. 84, 227-236; Tatsumi, E. et. al., 2021, Nat Commun 12, 5837; Watanabe, S. et al., 2019, Science 364, 6437: 268-272 

How to cite: Dirri, F., Palomba, E., Galiano, A., Longobardo, A., Gisellu, C., and Angrisani, M.: VIS-NIR reflectance analysis of (162173) Ryugu analogues mixtures and CC meteorites in the framework of Hayabusa2 mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-154, https://doi.org/10.5194/epsc2022-154, 2022.

Sensitive laboratory instruments on Earth are capable of determining the chemical, isotopic, mineralogical, structural, and physical properties of extraterrestrial samples from the macroscopic level down to the atomic scale, allowing to determine the origin and history of the material and answer questions far beyond the reach of current robotic technology. Sample return provides us with “ground truth” about the visited body, verifying and validating conclusions that can be drawn by remote sensing (both Earth-based and by spacecraft) and via landed instruments on other bodies. Returned samples can be compared to meteorites and cosmic dust using the same instrumentation, which apart from giving us clues about where those materials come from, potentially increases their scientific value as natural space probes. And finally, returned samples can be preserved for decades and used by future generations. The detailed investigation of the mineralogy and geochemistry of Ryugu plays a fundamental role in the understanding of its formation processes, and thereby gather further knowledge about the building blocks of the solar system. Based on the preliminary data from remote sensing measurements and laboratory-based measurements, Ryugu is rich in hydrated carbonaceous chondrite (CC) like material and more specifically it is very similar to Ivuna-like (CI) carbonaceous chondrites [1]. These meteorites are characterized by a high abundance of phyllosilicates and organic matter [2], which makes them have a low albedo. However, Ryugu seems to be even darker than CIs, as well as being more porous and fragile [1].

If Hayabusa2 samples are made available to our consortium, we will use a multi-pronged approach to achieve two main goals. The first goal is to address a fundamental challenge in the interpretation of remote sensing data which was seen during the initial analysis of the Hayabusa 2 samples. Observations of planetary surfaces using spectroscopy have shown subdued contrast compared to measurements performed under laboratory conditions on analog materials. A strong focus of the work performed at PSL over the last decade has been to understand - and if possible minimize - the difference between laboratory and remote sensing observations (e.g. [3,4,5,6]). Simulating the conditions on the target body as well as accurately reproducing the observing geometries have gone a long way towards that goal, however differences remain. A suggested explanation is the difference between terrestrial analog materials including even meteorites and the surfaces of planetary bodies. With Ryugu samples this hypothesis can be tested further, leading to a deeper understanding of the link between laboratory and remote sensing observations and thus benefiting not only the analysis of Hayabusa 2 data but of all remote sensing observations of planetary surfaces using spectroscopy.

The second goal building on this is an investigation of the mineralogy and organic matter of the samples collected by Hayabusa 2, to better: a) understand the evolution of the materials characterizing asteroid Ryugu and therefore advance our knowledge of the mineralogy of the protoplanetary disk and organic matter (OM); b) investigate the aqueous alteration that took place in the parent body that lead to its current chemical and mineralogical characteristics; c) compare the results with data collected from pristine carbonaceous chondrite meteorites rich in hydrated minerals and organic matter.

To prepare for measurements on Hayabusa 2 returned samples, we selected a small particle from the Mukundpura meteorite, a recently fallen meteorite that is considered as one of the best Ryugu analogs in the meteorite collection [7]. We have chosen a piece with a 4mm diameter, typical of the larger grains available in the Hayabusa 2 sample collection. We manufactured for this purpose a special sample holder for reflectance measurements in the FTIR spectrometer.

Figure 1.  (left): 4mm particle and the whole Mukundpura at PSL; (right): the 4mm particle in our sample holder.

Figure 1 shows the small 4 mm selected Mukundpura particle compared with the whole sample available at PSL and its special sample holder. We adapted our standard measurement set-up reducing the aperture to fit the size of the samples. With this configuration we obtained measurements as shown in Figure 2, where MIR spectrum of the 4mm Mukundpura particle, obtained reducing the aperture of our light source beam to the minimum, 0.25 mm is compared with a measurement of the same meteorite acquired with a much larger aperture (4mm, as standard).

Figure 2. Mukundpura bulk sample measured with traditional beam aperture of 4 mm (light-blue) and with reduced aperture (0.25 mm) on the small 4mm piece of the same meteorite. Below 9 µm we observe a lower reflectance of the piece compared to the bulk - reminiscent of what was observed in the preliminary investigation for the Hayabusa 2 sample.

It’s evident that with the reduced beam aperture, we are able to obtain high quality FTIR spectra of an Hayabusa 2 sample by just using our traditional spectroscopic set-up and compare to the thousands of spectra measured at PSL on a wide range of analogs including meteorites.

Raman spectroscopy complements IR spectroscopy in the determination of the mineralogical composition of the sample. It is performed in a contactless manner, and under neutral (e.g. nitrogen) atmosphere thanks to the long working distance objective. Figure 3 shows our tests on the Mukundpura particle; different measurement modes were used to reveal the presence of olivine, carbon, and magnesium silicates.

Figure 3. Example using the Mukundpura particle of an image scan of 30 points per line and 60 lines per image on a 120 x 80 µm area. The blue color denotes the presence of the olivine doublet (827 and 859 cm^-1) and red the presence of carbon D and G bands (1340 and 1568 cm^-1).

[1] Yada, T., Abe, M., Okada, T. et al., 2022. Nat Astron 6, 214–220. [2] Cloutis, E. A., et al., 2011. Icarus, 212:1.. [3] Maturilli, A., et al., 2016a. Earth, Planets and Space 68(1). [4] Maturilli, A., et al., 2016b. Earth, Planets and Space 68(1). [5] Beck, P., et al., 2018. Icarus 313: 124-13. [6] Yesiltas, et al., 2020. Meteoritics & Planetary Science, 55(11): 2404–2421. [7] Ray, D. and Shukla, A.D., 2018. PSS 151, 149-154.

How to cite: Maturilli, A., Schwinger, S., Bonato, E., Hamm, M., Helbert, J., Baque, M., Alemanno, G., and D'Amore, M.: Spectroscopic measurements on a Mukundpura meteorite grain as training for the analysis of Hayabusa2 returned samples, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-489, https://doi.org/10.5194/epsc2022-489, 2022.

Introduction: Meteorites, which are the remnants of our protoplanetary disk, provide a rich source of chemical information to investigate the origin of organic matter that have fallen on Earth and may have thus contributed to the emergence of life. Among meteorites, carbonaceous chondrites that contain organic matter are among the most primitive materials in the Solar System. Asuka 12236, found in Antarctica in 2012, has been classified as a member of the CM group. According to the first mineralogical analyses (Kimura et al., 2020, Nittler et al., 2021), Asuka 12236 is among the most primitive member of this group showing very few signs of aqueous alteration in its mineralogy.

Here, we have performed an overview of the soluble organic matter (SOM) present in this primitive meteorite, and compared it with other carbonaceous chondrites of the same family group. Two types of analysis were carried out on the SOM: a non-targeted analysis and then a targeted one on the basic so-called building blocks of life such as nucleobases and amino acids.

Methods: At first, we measured the global carbon content of our samples by elemental analysis using two grains of 2 mg each.

For the non-targeted high-resolution analysis of the SOM, 17 mg of the meteoritic material were used to extract the SOM with solvents allowing the preservation of meteorite organics (Schmitt-Kopplin et al. 2010). The fragment was crushed and successively extracted with dichloromethane, hexane and methanol at room temperature. The extracts were analyzed by FTICR (Fourier-Transform Ion Cyclotron Resonance) within a mass range of 150-1000 m/z.

For the analysis of the amino acids and nucleobases, 226 mg were extracted in water for 24h at 100°C. Aliquots were collected after centrifugation. Two UPLC-MS analyses have been performed (Serra et al., 2022) on these aliquots: the first was a screening from 50 to 750 m/z done with a Q-exactive Orbitrap coupled with a HILIC column. The second analysis has been done with a chiral column, allowing separation of targeted amino acids and information on a possible enantiomeric excess.  This chiral analysis is coupled with UPLC- Multiple Reaction Monitoring (MRM-MS) MS analyses.

Identification and quantification of the molecules were done by dosed addition using 54 amino acids and 5 nucleobases (Adenine, Guanine, Cytosine, Thymine, Uracil), ensuring the right identification of the isomers.  Note that our protocol does not include HCl hydrolysis step of the extracts, neither a derivatization procedure.

Results and Discussion: Elemental analysis (EA) done on 2 different fragments reveal the heterogeneity of our sample, in addition to the grains analyzed by Nittler et al., 2020, likely showing different alteration degrees in the chondrite (Fig. 1). We observe a correlation of carbon and nitrogen abundances in all grains of N/C ~ 0.05. From its H content, which can be extrapolated as the quantity of water, Asuka 12236 falls near the less altered CM chondrites, relatively close to the heated ones (EET and MIL CMs) (Alexander et al., 2012), while no sign of heat above 250 °C is observed on its mineralogy (Kimura et al., 2020).

Electrospray ionization in negative mode FTICR analyses of the methanol on Asuka SOM reveal a global chemical composition of C, H, N, and O molecules  up to 13211 different formulae (Fig. 2).  The CHONS family contains the major chemical compounds for 41 % followed with CHOS family for 34 %. Such sulfur rich compounds can be related to the high abundance of mineral sulfide observed in the Asuka matrix (Kimura et al., 2020) and found by elemental analysis (2.4 wt.%). Compared to others CMs, such as Murchison and Aguas Zarcas, measured with the same instrument, Asuka has a similar SOM diversity with more sulfur organic compounds. The Paris meteorite, also among the least altered chondrites (Marrocchi et al., 2014), has half in amount of compounds with a similar relative abundance in sulfur containing compounds as Asuka in its methanol SOM.  

The UPLC-HRMS method allows a rapid screening of small polar molecules. We observe a huge diversity of small compounds (<200m/z), with more intense signals than those obtained from Aguas Zarcas (Serra et al.; 2020).

Target analysis performed with chiral column allow the identification and quantification of roughly 40 different amino acids. None of the natural nucleobases has been firmly identified, but some masses seen by UPLC-HRMS method do correspond to possible nucleobases isomers (Ruf et al., 2019).

Overall, our analysis results in the observation of a very diverse compounds in Asuka 12236, similar to what is observed in more aqueously altered chondrites (Murchsion and Aguas Zarcas). In agreement with Glavin et al., 2020, we confirm the high concentration and diversity of amino acids, together with the identification of new ones in our extract of the meteorite (Fig. 3).

Such diversity, in amino acids and in global molecular composition, in addition to the quite high H wt.% indicates that the OM in Asuka 12236 has likely been altered during aqueous alteration, however still less than Murchison. It is also possible that Asuka 12236 presents more than one lithology, as seen with the three different results by EA, which can be related to the CI/CM clast seen in the matrix (Nittler et al., 2021). The chemical composition of the Asuka 12236 meteorite points toward a very rich and diverse composition but still needs further investigation in comparison to other meteorites to hypothesize on its origin and possible precise degree of alteration by aqueous processes.

Aknowledgements: We thank Philippe Clayes for the Asuka 12236 sample coming from the Asuka collection retrieved by expedition in Antartica by VUB-ULB and the Royal institute of the Natural Sciences in Bruxelles.

This study was partially funded by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) – Project-ID 364653263 – TRR 235 (CRC 235)

References:

Kimura. M. et al., (2020), Polar Science, (26), p100565.

Marrocchi et al. (2014), Meteoritics and planetary science 49.

Nittler et al., (2021), Meteoritics and planetary science 56

Ruf et al., (2019). The Astrophysical Journal Letters, 887

Schmitt-Kopplin. P. et al., (2010), PNAS, 107 (7) p 2763-2768

Serra. C. et al., (2022), Talanta (Oxford), (243), p123324

How to cite: Serra, C., Vinogradoff, V., Poinot, P., Duvernay, F., Le Sergeant d'Hendecourt, L., and Schmitt-Kopplin, P.: Overview of the organic matter present in Asuka 12236: a primitive meteorite?, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-546, https://doi.org/10.5194/epsc2022-546, 2022.

1/ Introduction

The incorporation and evolution of nitrogen (N) in the early Solar System, as well as the origin of terrestrial nitrogen, are still very poorly understood. Across the Solar System, the isotopic composition of nitrogen is far from being uniform ­(from δ15N = –387 ± 8‰ in the Solar Wind to δ15N = +850 ± 150‰ in nitrogen species in cometary coma) and seems to reflect different processes leading to distinct isotopic reservoirs [e.g., 1]. As carbonaceous chondrites (CC) are the richest in volatiles [2] among primitive meteorites, the measurements of their nitrogen isotopic composition are a key to investigate the origins and evolutions of this element in the Solar System.

As for CCs [3], the nitrogen in comets is considered to be mainly present in the refractory organic material [4]. However, nitrogen in the form of ammonium salts have been identified on comet 67P/Churyumov-Gerasimenko [5] and may constitute the dominant reservoir of nitrogen in comets [5, 6]. Ammonium may also be present on several asteroids [5, 7] and might be present in Hayabusa2-returned samples among NH-rich compounds [8]. Ammonium could therefore constitute a dominant nitrogen reservoir of these objects, and may have been delivered in abundance to Earth through carbonaceous chondrites.

In 1864, 0.1wt% of ammonium was detected in the Orgueil meteorite, just after its fall [9], but has never been reported since then. Is the ammonium detected in 1864 still present in the meteorite nowadays? Is it a terrestrial contamination? If extraterrestrial, how much nitrogen is in the form of ammonium in Orgueil? How is nitrogen partitioned between ammonium, soluble and insoluble organic compounds? What are the genetic links between these nitrogen-containing phases? These are the questions we seek to address with the present work.

2/ Method

Because the Orgueil meteorite is known to be altered by the terrestrial environment [10] we have analysed two samples of Orgueil, that have been stored in different conditions. The so-called “Orgueil-Flask” (OF) is material recovered after the fall in 1864 and kept in a tightly sealed flask in a private collection. By contrast, the so-called “Orgueil-Museum” (OM) is a raw chip from the Orgueil sample kept in a sealed bell-jar, but possibly leaking, at the Museum Victor Brun de Montauban (France). OM grains/fragments are covered by relatively bright effloresced sulfates, which are minor in OF grains, indicating that the OF sample is probably less terrestrially altered.

To avoid any contamination by terrestrial ammonia, we have developed a contamination-free protocol to extract, quantify and measure the isotopic composition of nitrogen in Orgueil water-soluble ammonium (Figure 1). The meteorite is ground and solubilised in water to extract water-soluble ammonium. Grinding the meteorite fragment can heat the material, potentially leading to the evaporation of ammonium and/or to the decomposition of organic molecules forming ammonium or ammonia [11, 12, 13]. To overcome these issues and solubilise as much ammonium as possible, the meteorite fragment is ground under cryogenic conditions in a hermetic jar containing water ice. After grinding and water melting, ten series of leaching by ultra-sonification, followed by centrifugation, collection of the supernatant phase and re-solubilisation of the ammonium contained in the remaining powder are performed to extract all the water-soluble ammonium. The resulting solutions are analysed by Ion-exchange Chromatography (IC) and Isotopic Ratio Mass Spectrometer (IRMS) to quantify the ammonium content and measure its N-isotopy.

To investigate the partition of nitrogen in the meteorite, the nitrogen abundance and isotopic composition of the bulk samples and of the Insoluble Organic Material (IOM) extracted from these samples (adapted from the method described in [14]) are also measured by IRMS.

3/ Main results and conclusions

Duplicate analyses of the least altered sample (OF) reveal the presence of water-soluble ammonium at a concentration ranging from 0.053 to 0.083 weight percent by mass of meteorite with a mean value of 0.068 ± 0.015 wt% (Table 1). This concentration corresponds to a mean proportion of 28 ± 4% of the total nitrogen in Orgueil. This ammonium may come from ammonium salts and/or ammoniated phyllosilicates. The δ¹⁵N mean value of +132‰ confirm the extra-terrestrial origin of ammonium. The differences of isotopic composition observed between the N-bearing phases (Table 1) suggest a different origin of the nitrogen contained in organic matter and water-soluble ammonium.

Our results confirm that ammonium constitutes a substantial nitrogen reservoir in Orgueil. More broadly, studying the repartition of the nitrogen in the N-bearing phases, including ammonium, and their genetic links will help us to reveal the incorporation of nitrogen in the Solar System and ultimately on Earth.

4/ Acknowledgments

This work has been supported by grants from Labex OSUG@2020 (Investissements d’avenir – ANR10 LABX56) and from the Programme National de Planétologie (PNP) of CNRS-INSU co-funded by CNES.

References:

[1]   Füri and Marty, 2015, Nature Geoscience 8, 515‑22

[2]   Marty et al., 2016, Earth and Planetary Science Letters 441, 91‑102

[3]   Alexander et al., 2017, Geochemistry 77, 227‑56

[4]   Fray et al., 2017, MNRAS 469, S506–S516

[5]   Poch et al., 2020, Science 367, 7462

[6]   Altwegg et al., 2020, Nature Astronomy 4, 533‑40

[7]   De Sanctis et al., 2015, Nature 528, 241‑44.

[8]   Pilorget et al., 2022, Nature Astronomy 6, 221‑25

[9]   Cloëz, 1864, Comptes Rendus de l’Académie des Sciences Paris 58, 37-42, 986–988

[10] Gounelle and Zolensky, 2001, Meteoritics & Planetary Science 36, 1321‑29

[11] Pizzarello et al., 1994 Geochimica et Cosmochimica Acta 58, 5579‑87

[12] Pizzarello and Williams, 2012, The Astrophysical Journal 749, 161

[13] Pizzarello and William, 2009, Geochimica et Cosmochimica Acta 73, 2150‑62

[14] Gardinier et al., 2000, Earth and Planetary Science Letters 184, 9‑21

How to cite: Laize-Générat, L., Soussaintjean, L., Poch, O., Bonal, L., Savarino, J., Caillon, N., Ginot, P., Vella, A., Flandinet, L., Gounelle, M., and Bizzaro, M.: Ammonium is a significant reservoir of nitrogen in the Orgueil meteorite, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-837, https://doi.org/10.5194/epsc2022-837, 2022.

Introduction

Comets are the most primitive bodies of the solar system [1]. They are composed of low density material: mainly dust and ice. A better understanding of their composition is of particular interest to improve the comprehension of the composition of the material composing the forming solar system. Nevertheless, because of detection issues, the composition of its nucleus is only poorly known even eight years after the landing of the Philae probe from the European Space Agency (ESA) Rosetta mission. Most insights on the organic composition of 67P/Churyumov-Gerasimenko are coming from indirect analysis estimating that around 45 % of a comet is composed of organic matter ([2],[3]).

Laboratory experiments show similarities with the organic matter observed in comets [4]. Astrochemical experiments are thus a promising approach to cover this lack of data. Experiments simulating the chemical reactivity occurring on icy grains initially composed with volatile molecules such as H2O, NH3, methanol (MeOH) give information into the refractory [5] and volatile [6] organic composition that are formed in such astrophysical environments. Those experiments suggest the presence of a large organic diversity [7]. Previous work showed the correlation between the initial composition of these ices and either the volatile organic compounds (VOCs) composition [8] or the refractory organic material [9]. In this presentation, we will give the first experimental description of the correlations that exist between both three phases: the primitive ice composition, the refractory and the gas phase. 

Method

All samples were synthesized using the MICMOC experiment [10]. It is a vacuum chamber (~10^-7 mbar) where different ice compositions of H₂O, NH₃ and methanol (MeOH) were irradiated at Lyman α (121 nm) at 77 K for 5,5 h at a fixed irradiation rate of ~7 photon/MeOH. Then, 92 mbar of argon were added before the sample was warmed up to ~300 K. Four ice compositions were tested : a benchmark experiment (Ref.) with ratio 3:1:2 (H₂O:MeOH:NH₃); a H2O-rich sample, 8:1:2; a NH3-rich sample, 2:1:5; and a MeOH-rich sample, 2:5:3.

VOCs are recovered using an extra cryogenic trap coupled to a valve system for GC-EI-FT-Orbitrap analysis [11]. Three replicates are made for each ice composition. The cumulation of the three residual phases from all samples is then extracted and dissolved 10 times into methanol before positive ESI-FT-ICR. More details on the apparatus characteristics can be found in [12].

To extract correlations between all three phases (initial ice, refractory and gas), principal component analysis (PCA) were performed on the dataset standardized by variable with following characteristics :

• For the gas phase (Figure 1A): individuals are the triplicates of GC-EI-FT-Orbitrap analysis with 150 chromatographic peak areas as variables;
• For the refractory phase (Figure 1B): individuals are the analysis of methanol solubilized refractory material injected using positive ESI-FT-ICR with between 4126 to 12814 extracted exact mass peak area as variables.

Preliminary results and conclusions

PCA is a mathematical tool to find the smartest plan to differentiate individuals in a multiple variable hyperspace. Figure 1 displays the plan with highest differences from those two datasets. Axes 1 and 2 are mostly enough to discriminate samples according to their initial composition for both gas phase (Figure 1A)  and residual phase (Figure 1B). As most individual ices are present in different zones, it proves the organic composition of each phase allows to find correlation between them.

More specifically, in the gas phase (Figure 1A) only three zones can be determined : the first one contains only NH3-rich ices, the second one MeOH-rich ices and the third one both the benchmark experiment (Ref.) and H2O-rich ices. Consequently, H₂O, NH₃ and MeOH seem to have different impacts on the volatile organic compounds: H₂O seems to be less impactful on the first and second principal axes while only the third axes can discriminate it from the other zones.

Finally, all three parameters can be separated using ACP on residual phase, proving significant differences extracted from the intensity and compound nature detected by positive ESI-FT-ICR. All together, this suggests a high correlation between all three phases regarding their organic compound composition.

Shortly :

• On the gas phase : NH₃ hinders all volatile productions including nitriles, H₂O has little impact on the gas composition with respect to the benchmark experiment.
• On the refractory phase : NH₃ and H₂O are changing the nature of organics produced and making global  ESI-FT-ICR intensity. H₂O is the ice that’s producing the smaller organic diversity (tree time less compounds detected).
• In both gas and residual phase : MeOH has little impact on the final organic compound type, but enhances the total amount of them.

Figure 1. Principal component analysis (PCA) of results from each sample. In A) individuals are the triplicates of GC-EI-FT-Orbitrap analysis with chromatographic peak areas as variables. In B) individuals are each four analyses of methanol solubilized refractory material injected using positive ESI-FT-ICR with exact mass peak area as variables. Samples are labeled according to the compound exhausted in the initial composition of the ice with respect to the benchmark experiment (Ref.); H₂O for the H₂O-enriched sample; NH₃ for the NH₃-enriched sample and a MeOH for the MeOH-enriched sample.

Bibliography :

[1] M. J. Mumma and S. B. Charnley, Annu. Rev. Astron. Astrophys., vol. 49, no. 1, pp. 471–524, 2011.    

[2] J.-L. Bertaux and R. Lallement, MNRAS, vol. 469, no. Suppl_2, pp. S646–S660, 2017.

[3] K. Varmuza et al., J Chemom, vol. 34, no. 4, 2020.

[4] F. Duvernay et al., ApJ, vol. 791, no. 2, p. 75, 2014.    

[5] G. Danger et al., GCA, vol. 118, pp. 184–201, 2013. 

[6] N. Abou Mrad et al., Anal. Chem., vol. 86, no. 16, pp. 8391–8399, 2014.

[7] A. Ruf et al., Life, vol. 9, no. 2, p. 35, 2019.   

[8] N. Abou Mrad et al., ApJ, vol. 846, no. 2, p. 124, 2017.  

[9] A. Fresneau et al., ApJ, vol. 837, no. 2, p. 168, 2017.

[10] L. d’Hendecourt and E. Dartois, Spectrochim. Acta A Mol. Biomol. Spectrosc., vol. 57, no. 4, pp. 669–684, Mar. 2001. 

[11] T. Javelle et al., J. Chromatogr. A, vol. 1652, p. 462343, 2021.    

[12] P. Schmitt-Kopplin et al., Anal. Chem., vol. 82, no. 19, pp. 8017–8026, 2010. 

How to cite: Javelle, T., Schmitt-Kopplin, P., and Danger, G.: Correlations between cometary ice composition and their refractory and gas organic diversity: clues from laboratory experiments, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1018, https://doi.org/10.5194/epsc2022-1018, 2022.

In the CoPhyLab at the TU Braunschweig, the goal is to simulate the physical behaviour of comets on Earth. Therefore, we are currently producing pebbles from silicate dust and water ice in order to subsequently investigate their properties and behaviour in various experiments. The pebbles we are producing consist of a mixture of water ice and dust, but also of pure water ice.

Figure 1: Sieved pebbles with diameters of 1mm to 1.6mm consisting of a mixture of dust and water ice with a ratio 3:1.

The materials are mixed and then shaken while low temperatures are secured. For a homogenous mixture some nitrogen is added during the mixing procedure. In order to be able to form the largest possible number of pebbles from a mixture, it is necessary to understand the process of pebble formation. Therefore, we have studied the formation behaviour of pebbles from mixtures with different mixing ratios and by using different shaking techniques. Recent experiments have shown that mixtures with different weight ratios of dust-to-water ice can form pebbles. Also, adding a certain amount of graphite to darken the mixture has no effect on the formation process.

To study and to quantify the properties of the pebbles, such as compressive strength and thawing behaviour, it is important to know the particle size distribution. For this purpose, the pebbles must be sieved. This has been successfully carried out at the TU Braunschweig. With the samples obtained in this way, it has already been possible to gain initial insights into, among other things, the thawing behaviour and porosity of the pebbles. It was found, for example, that pebbles with an higher dust content retain their structure and a baking effect occurs, which leads to a hardening of the material, whereas pebbles with a low dust content collapse.

During this conference we will present our pebble making technique and our findings about the formation of pebbles. Further, we want to introduce the audience to our shaking machine. The latest results about the thawing behaviour as well as other properties of the pebbles will be presented, too. 

How to cite: Brecher, N., Kreuzig, C., Gundlach, B., and Blum, J.: The Production of Dust-Ice-Pebbles, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-526, https://doi.org/10.5194/epsc2022-526, 2022.

Sublimation of volatile materials causes a pressure build-up in the surface layers of comets, which then leads to outgassing and to the ejection of particles. To investigate this behavior in more detail, an experimental setup was developed as part of the CoPhyLab campaign [1]. With this setup different comet analogue samples are exposed to an artificial Sun to simulate cometary activity. The first experiments are conducted with pure water ice samples only since water ice comprises the bulk of volatile materials in most comets [2] and pure samples provide a well comprehensible starting point to model the development of the experiments.

Thanks to our experiments we were able to observe, for the first time, that the sublimation of pure water ice (ice without any additional components, or impurities) can eject solid grains. Hence, the ejection of water ice grains does not require the presence of a more volatile species as suggested by [3]. In our experiments, the trajectories of the grains were recorded with a high-speed camera and subsequently evaluated with respect to their motion behavior using a particle tracking routine (Fig. 1).

Fig.1:   Superimposed image of all “well-tracked” particle trajectories of one experiment over the observed sample surface.

The ejected particles possess terminal speeds of about 1 m/s. Further, we found that the terminal particle velocity, as well as the total activity, depends directly on the insolation. Moreover, the observed trajectories were modeled by using gas-drag laws to derive an estimate for the sublimation pressure inside the samples [4].

The knowledge gained from these experiments will be used both in a larger experimental setup [5] and in further experiments including mixtures of water ice with dust and with super-volatiles such as CO2.

References

[1] Gundlach, B., “CoPhyLab: recent and future experiments - an overview”, 2020. doi:10.5194/epsc2020-218.

[2] Bockelée-Morvan, D., “An Overview of Comet Composition”, in The Molecular Universe, 2011, vol. 280, pp. 261–274. doi:10.1017/S1743921311025038.

[3] A'Hearn, M. F., “EPOXI at Comet Hartley 2”, Science, vol. 332, no. 6036, p. 1396, 2011. doi:10.1126/science.1204054.

[4] Capelo, H. L., “Observation of aerodynamic instability in the flow of a particle stream in a dilute gas”, Astronomy and Astrophysics, vol. 622, 2019. doi:10.1051/0004-6361/201833702.

[5] Kreuzig, C., “The CoPhyLab comet-simulation chamber”, Review of Scientific Instruments, vol. 92, no. 11, 2021. doi:10.1063/5.0057030.

How to cite: Molinski, N., Kreuzig, C., Blum, J., Capelo, H., Pommerol, A., and Gundlach, B.: Particle tracking analysis of ejected water-ice grains from pure ice cometary analogue samples, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-383, https://doi.org/10.5194/epsc2022-383, 2022.

In the previous years, the CoPhyLab* has established an experimental environment that makes it possible to simulate the activity of comets in the best way possible. Nevertheless, it is vital to know all parameters that have an impact on the outcome of such experiments, as well as parallelly developed models. Therefore, several smaller experiments provide important knowledge, especially about the used comet analogue, the CoPhyLab-dust.

With the gas-flow experiment we conduct in Graz it is possible to learn about the permeability and effusion of gas through porous media in a dry environment. In this presentation we will present how that works and what challenges we needed to overcome to achieve good scientific outcomes.
With the results of this experiment a special case of the dusty-gas model, established by Evans et al. 1961 [1], will be tested in high vacuum.

A vacuum chamber with two compartments, which are connected via a tube that holds the tested sample, is used for the experiment (see Figure 1). In both compartments pressure sensors are mounted onto the chamber. For our measurements we use two different gas-flow controllers with different gas-flow ranges to cover a wide pressure range. As this is a continuing work, the theoretical scheme was established by Schweighart et al. 2021 [2]. According to Equation 10 from their work, knowledge of the upstream and downstream pressure as well as the mass flux flowing through the sample, allows us to measure the Knudsen diffusion Dk as well as the permeability B of the sample.

Figure 1: Experiment Setup

Because gas-flow must be known precisely, a leakage of gas into the chamber, which is always there could have an influence on the evaluation of the results. Therefore, a bleed-up test was performed. To work with porous media is a difficult task. Therefore, measurements with round glass beads, with a predictable packing behavior, were performed.

We found that the results deviate from the regression using the dusty gas model at lower pressures or smaller gas flows (see Figure 2). There is a systematic decrease in pressure at smallest gas flows. We are currently investigating the possible causes for this behavior.
On the one hand, we consider if the deviation could be explained by set up related properties, like a leak in the chamber or a systematic offset on the gas flow. On the other hand, an outgassing of volatiles or a temperature dependence are possibilities we are looking into. Nevertheless, we already gain high confidence results in the measured pressure regime. In future we will investigate how those results compare to theoretical models, which consider the porosity and the tortuosity of such porous samples (e.g., Asaeda et al. 1974 [3]).

Figure 2: Experimental results for an asteroid analogue sample,
with the apparent Diffusion D_app depending on the mean pressure within the tested sample.

Acknowledgements:

This work is carried out in the framework of the CoPhyLab project funded by the D-A-CH programme (DFG GU 1620/3-1 and BL 298/26-1 / SNF 200021E 177964 / FWF I 3730-N36).

References:

[1] Evans III, R. B., G. M. Watson, and E. A. Mason. "Gaseous diffusion in porous media at uniform pressure." The journal of chemical physics 35.6 (1961): 2076-2083.

[2] Schweighart, M., et al. "Viscous and Knudsen gas flow through dry porous cometary analogue material." Monthly Notices of the Royal Astronomical Society 504.4 (2021): 5513-5527.

[3] Asaeda, Masashi, Shigeyuki Yoneda, and Ryozo Toei. "Flow of rarefied gases through packed beds of particles." Journal of Chemical Engineering of Japan 7.2 (1974): 93-98.

*The CoPhyLab (Comet Physics Laboratory): https://www.cophylab.space/index.php?id=home

How to cite: Zivithal, S., Kargl, G., Macher, W., Laddha, S., Güttler, C., Sierks, H., Blum, J., and Gundlach, B. and the CoPhyLab-Team: Experimental Characterization of Gas Flow Properties of Dry Refractory Materials, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-930, https://doi.org/10.5194/epsc2022-930, 2022.