¹M.PineauaL.Le Deit,²B.Chauviré,³J.Carter,¹B.Rondeau,¹N.Mangold
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113706]
¹Laboratoire de Planétologie et Géodynamique, CNRS UMR 6112, Université de Nantes, Université d’Angers, Nantes, France
²Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, Grenoble, France
³Institut d’Astrophysique Spatiale, CNRS UMR 8617, Université Paris-Sud, Orsay, France
Copyright Elsevier

Hydrated silica detected on the martian surface, from both orbital and in-situ data, is an indicator of past aqueous conditions. On Earth, several near infrared (NIR) spectral criteria can be used to discriminate silica phases (e.g. opal-A, opal-CT and chalcedony) and their formation processes. We have applied these spectral criteria to Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data in order to investigate the geological origin of hydrated silica on Mars. We used two spectral criteria: (i) the crystallinity spectral criteria on the 1.4- and 1.9 μm absorption bands to distinguish between amorphous (opal-A and hydrated glasses) and more crystalline (opal-CT and chalcedony) varieties of silica, and (ii) the Concavity-Ratio-Criterion (CRC) to differentiate opals of hydrothermal origin from weathering origin. We first adapted the CRC measurements on terrestrial samples to make them comparable to CRISM measurements on Mars: we resampled our terrestrial spectra down to the CRISM resolution, and tested the martian pressure effect on spectral signatures. Then, we selected several areas over nine sites where hydrated silica has been detected on Mars, on the basis of good quality detections. Our results show that two main types of spectra can be distinguished, and these are consistent with two distinct geomorphological contexts proposed by Sun and Milliken (2018): amorphous and/or dehydrated silica-bearing bedrock deposits, and more crystalline and/or hydrated silica-bearing aeolian deposits. The concavity criterion also indicates silica origins that are in agreement with most of the hypothesized geological origins proposed in the literature. Although these results need further strengthening, they are promising for the use of NIR signatures as means of investigating the processes of hydrated silica on Mars.

^1,2Shoichi Oshino,³Yasuhiro Hasegawa,^1,4Shigeru Wakita,^1,5,6Yuji Matsumoto
The Astrophysical Journal 884, 37 Link to Article [DOI
https://doi.org/10.3847/1538-4357/ab40bc]
¹Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan
²Institute for Cosmic Ray Research, University of Tokyo, Hida, Gifu 506-1205, Japan
³Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
⁴Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan
⁵Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba 275-0016, Japan
⁶Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan

Understanding chondrule formation provides invaluable clues about the origin of the solar system. Recent studies suggest that planetesimal collisions and the resulting impact melts are promising for forming chondrules. Given that the dynamics of planetesimals is a key in impact-based chondrule formation scenarios, we here perform direct N-body simulations to examine how the presence of Jupiter affects the properties of chondrule-forming collisions. Our results show that the absence/presence of Jupiter considerably changes the properties of high-velocity collisions whose impact velocities are higher than 2.5 km s⁻¹. High-velocity collisions occur due to impacts between protoplanets and planetesimals for the case without Jupiter; for the case with Jupiter, the eccentricities of planetesimals are pumped up by the secular and resonant perturbations from Jupiter. We also categorize the resulting planetesimal collisions and find that most high-velocity collisions are classified as grazing ones for both cases. To examine the effect of Jupiter on chondrule formation directly, we adopt the impact-jetting scenario and compute the resulting abundance of chondrules. Our results show that for the case without Jupiter, chondrule formation proceeds in the inside-out manner, following the growth of protoplanets. If Jupiter is present, the location and timing of chondrule formation are determined by Jupiter’s eccentricity, which is treated as a free parameter in our simulations. Thus, the existence of Jupiter is the key parameter for specifying when and where chondrule formation occurs for impact-based scenarios.

¹Emmanuel Jacquet,^1,2Francesco C. Pignatale,²Marc Chaussidon,²Sébastien Charnoz
The Astrophysical Journal 884, 32 Link to Article [DOI
https://doi.org/10.3847/1538-4357/ab38c1]
¹Muséum national d’Histoire naturelle, UMR 7590, CP52, 57 rue Cuvier, F-75005, Paris, France
²Institut de Physique du Globe de Paris (IPGP), 1 rue Jussieu, F-75005, Paris, France

The isotopic heterogeneity of the solar system shown by meteorite analyses is more pronounced for its earliest objects, the calcium–aluminum-rich inclusions (CAIs). This suggests that it was inherited from spatial variations in stardust populations in the protosolar cloud. We model the formation of the solar protoplanetary disk following its collapse and find that the solid-weighted standard deviation of different nucleosynthetic contributions in the disk is reduced by one order of magnitude compared to the protosolar cloud, whose successive isotopic signatures are fossilized by CAIs. The enrichment of carbonaceous chondrites in r-process components, whose proportions are inferred to have diminished near the end of infall, is consistent with their formation at large heliocentric distances, where the early signatures would have been preferentially preserved after outward advection. We also argue that thermal processing had little effect on the (mass-independent) isotopic composition of bulk meteorites for refractory elements.

^1,2Francesco C. Pignatale,¹Emmanuel Jacquet,²Marc Chaussidon,²Sébastien Charnoz
The Astrophysical Journal 884, 31 Link to Article [DOI
https://doi.org/10.3847/1538-4357/ab3c1f]
¹Muséum national d’Histoire naturelle, Institut de Minéralogie, Physique des Matériaux et de Cosmochimie, Département Origines et Evolution, UMR 7590, CP52, 57 rue Cuvier, F-75005, Paris, France
²Université de Paris, Institut de Physique du Globe de Paris, CNRS, 1 rue Jussieu, F-75005 Paris, France

The short-lived radionuclide 26Al is widely used to determine the relative ages of chondrite components and timescales of physical and thermal events that attended the formation of the solar system. However, an important assumption for using 26Al as a chronometer is its homogeneous distribution in the disk. Yet, the oldest components in chondrites, the Ca–Al-rich inclusions (CAIs), which are usually considered as time anchors for this chronometer, show evidence of 26Al/27Al variations independent of radioactive decay. Since their formation epoch may have been contemporaneous with the collapse of the parent cloud that formed the disk, this suggests that 26Al was heterogeneously distributed in the cloud. We model the collapse of such a heterogeneous cloud, using two different 26Al distributions (monotonic and nonmonotonic), and follow its redistribution in the first condensates and bulk dust that populate the forming disk. We find that CAIs inherit the 26Al/27Al ratio of the matter infalling at the time of their formation, so that variations of 26Al/27Al among primordial CAIs can be accounted for, independently of radioactive decay. The prevalence of a canonical ratio among them and its necessity for the differentiation of the first planetesimals suggest a (monotonic) scenario where 26Al sharply rose relatively close to the center of the protosolar cloud and essentially remained at a high level outward (rather than decreased since). As the 26Al abundance would be relatively homogeneous after cessation of infall, this would warrant the use of the Al–Mg chronometer from the formation of “regular” CAIs onward, to chondrules and chondrite accretion.

¹Omaira González-Martín,²Josefa Masegosa,³Ismael García-Bernete,^4,5Cristina Ramos Almeida,^4,5José Miguel Rodríguez-Espinosa,²Isabel Márquez,¹Donaji Esparza-Arredondo,¹Natalia Osorio-Clavijo,^1,6Mariela Martínez-Paredes,¹César Victoria-Ceballos,¹Alice Pasetto,⁷Deborah Dultzin
The Astrophysical Journal 884, 10 Link to Article [DOI
https://doi.org/10.3847/1538-4357/ab3e6b]
¹Instituto de Radioastronomía y Astrofísica (IRyA-UNAM), 3-72 (Xangari), 8701, Morelia, Mexico
²Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n E-18008, Granada, Spain
³Instituto de Física de Cantabria (CSIC-UC), Avenida de los Castros, E-39005 Santander, Spain
⁴Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea, s/n, E-38205 La Laguna, Spain
⁵Departamento de Astrofísica, Universidad de La Laguna (ULL), E-38205 La Laguna, Spain
⁶Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
⁷Instituto de Astronomía (IA-UNAM), Apartado Postal 70-264, 04510, Mexico DF, Mexico

At distances from the active galaxy nucleus where the ambient temperature falls below ~1500–1800 K, dust is able to survive. It is thus possible to have a large dusty structure present that surrounds the active galaxy nucleus. This is the first of two papers aiming at comparing six dusty torus models with available spectral energy distributions, namely, Fritz et al., Nenkova et al., Hönig & Kishimoto, Siebenmorgen et al., Stalevski et al., and Hönig & Kishimoto. In this first paper we use synthetic spectra to explore the discrimination between these models and under which circumstances they allow us to restrict the torus parameters, while our second paper analyzes the best model to describe the mid-infrared spectroscopic data. We have produced synthetic spectra from current instruments GTC/CanariCam and Spitzer/IRS and future James Webb Space Telescope (JWST)/MIRI and JWST/NIRSpec instruments. We find that for a reasonable brightness (F _{12 μm} > 100 mJy) we can actually distinguish among models except for the two pairs of parent models. We show that these models can be distinguished based on the continuum slopes and the strength of the silicate features. Moreover, their parameters can be constrained within 15% of error, irrespective of the instrument used, for all the models except Hönig & Kishimoto. However, the parameter estimates are ruined when more than 50% of circumnuclear contributors are included. Therefore, future high spatial resolution spectra such as those expected from JWST will provide enough coverage and spatial resolution to tackle this topic.

^1,2Ai-Cheng Zhang,³Noriyuki Kawasaki,³Minami Kuroda,¹Yang Li,⁴Hua-Pei Wang,⁵Xue-Ning Bai,⁶Naoya Sakamoto,⁷Qing-Zhu Yin,^3,6,8Hisayoshi Yurimoto
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2020.02.014]

¹State Key Laboratory for Mineral Deposits Research and School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
²CAS Center for Excellence in Comparative Planetology, China
³Department of Natural History Sciences, Hokkaido University, Sapporo 060-0810, Japan
⁴School of Earth Sciences, Chinese University of Geosciences, Wuhan 430074, China
⁵Institute for Advanced Study and Department of Astronomy, Tsinghua University, Beijing 100084, China
⁶Isotope Imaging Laboratory, Creative Research Institution, Hokkaido University, Sapporo 001-0021, Japan
⁷Department of Earth and Planetary Sciences, University of California Davis, One Shields Avenue, Davis, California 95616, USA
⁸Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 252-5210, Japan
Copyright Elsevier

Most meteorites are believed to be chips from planetesimals and can provide clues to constrain the chemical evolution and dynamic history of the early Solar System. In this study, we report two unique fragments (ALF-1 and ALF-2) enclosed in the CH3 carbonaceous chondrite Sayh al Uhaymir 290. These two fragments are dominated by Ca,Fe-rich olivine with various amounts of Al,Ti-rich augite, anorthite, oxide minerals, Ca-phosphate mineral, FeNi metal, enstatite, and less Al,Ti-rich augite. The Ca-Mg-Fe systematics and Fe/Mn ratios of olivine grains in the two fragments are similar to that of the volcanic angrites. These similar features imply that the parent body of the two fragments might have bulk chemistry, oxygen fugacity, and differentiation resembling the angrite parent body. However, high-precision SIMS measurements reveal oxygen isotope compositions Δ¹⁷O=0.91 ±0.18 ‰ (2σ) of olivine in the two fragments are distinctly different from that of known angrite meteorites, possibly representing a new type of basaltic planetesimal.

The two fragments also have a few mineralogical features distinct from angrite meteorites. They include: (1) the lack of a typical igneous texture; (2) the coexistence of two spatially associated Al,Ti-rich augites with different contents of CaO, Al₂O₃, MgO, and P₂O₅; (3) the presence of an enstatite-dominant rim in ALF-1; (4) the presence of a Cr,Mn-rich margin in ALF-1; and (5) complex microscale heterogeneity in oxide minerals. We argue that these features could be due to complex thermal histories in their parent body and/or after ejection from their parent body. Among these features, the Mn,Cr-rich margin and the enstatite-dominant rim in ALF-1 can be best explained with thermal events in nebular settings. This implies that the differentiation of the parent body of the two fragments might have taken place prior to the dissipation of the nebular gas.

¹Zhukovska, S.
Proceedings of the International Astronomical Union 2019, 258-264 Link to Article [DOI: 10.1017/S1743921318007561]
¹Max Planck Institute for Astrophysics, Karl-Schwarzshild-Str. 1, Garching, 85748, Germany

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^1,2Pignatale, F.C.,²Charnoz, S.,²Chaussidon, M.,¹Jacquet, E.
Proceedings of the International Astronomical Union 2019, 137-140 Link to Article [DOI: 10.1017/S1743921318008311]
¹Muséum National d’Histoire Naturelle, UMR 7590, CP52, 57 rue Cuvier, Paris, 75005, France
²Institut de Physique du Globe de Paris (IPGP), 1 rue Jussieu, Paris, 75005, France

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^1,2J.N.Rasera,¹J.J.Cilliers,²J.-A.Lamamy,¹K.Hadler
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.104879]
¹Earth Science and Engineering, Imperial College London, SW7 2AZ, United Kingdom
²Ispace Europe S.A., Rue de l’Industrie 5, L-1811, Ville de Luxembourg, Luxembourg

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¹Young, E.D.,¹Elmegreen, B.G.,¹Tóth,L.V.,¹Güdel, M.
Proceedings of the International Astronomical Union
2019,70-77 Link to Article [DOI: 10.1017/S1743921319001777]
¹Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, United States

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