^1,2Kołodziej, M.,¹Śniadecki, Z.,¹Musiał, A.,³Pierunek, N.,⁴Ivanisenko, Y.,⁵Muszyński, A.,¹Idzikowski, B.
Journal of Magnetism and Magnetic Materials 502, 166577 Link to Article [DOI: 10.1016/j.jmmm.2020.166577]
¹Institute of Molecular Physics, Polish Academy of Sciences, Mariana Smoluchowskiego 17, Poznań, 60-179, Poland
²NanoBioMedical Centre, Adam Mickiewicz University in Poznań, Wszechnicy Piastowskiej 3, Poznań, 61-614, Poland
³Quantum Electronics Laboratory, Faculty of Physics, Adam Mickiewicz University, Uniwersytetu Poznańskiego 2, Poznań, 61-614, Poland
⁴Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, D-76344, Germany
⁵Institute of Geology, Adam Mickiewicz University, Bogumiła Krygowskiego 12, Poznań, 61-680, Poland

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Allegretta, I.,²Marangoni, B.,³Manzari, P.,¹Porfido, C.,¹Terzano, R.,⁴De Pascale, O.,⁴ Senesi, G.S.
Talanta 212, 120785 Link to Article [DOI: 10.1016/j.talanta.2020.120785]
¹Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi di Bari “Aldo Moro”, Via Amendola 165/A, Bari, 70126, Italy
²Physics Institute, Federal University of Mato Grosso do Sul, P.O. Box 549, Campo Grande, MS 79070-900, Brazil
³Agenzia Spaziale Italiana, via del Politecnico, Roma, 00133, Italy
⁴CNR – Istituto per la Scienza e Tecnologia dei Plasmi (ISTP) – Sede di Bari, Via Amendola 122/D, Bari, 70126, Italy

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Gismelssed, A.,²Okunlola, O.,¹Al-Rawas, A.,¹Yousif, A.,²Oyedokun, M.,³Adetunji, J.,¹Widatallah, H.,¹Elzai, M.
Hyperfine Interactions 241, 22 Link to Article [DOI: 10.1007/s10751-019-1683-7]
¹Physics Department, College of Science, Sultan Qaboos university, Muscat, Oman
²Department of Geology University of Ibadan, Ibadan, Nigeria
³School of Environmental Sciences, University of Derby, Kedleston Road, Derby, DE22 1GB, United Kingdom

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹Ferreira, L.M.G.,²Alves, E.I.,³Gonçalves, M., Costa,¹B.F.O.
Hyperfine Interactions 241, 19 Link to Article [DOI: 10.1007/s10751-019-1685-5]
¹CFisUC, Physics Department, University of Coimbra, Coimbra, P-3004-516, Portugal
²CITEUC and Department of Earth Sciences, University of Coimbra, Coimbra, P-3040-004, Portugal
³NEO SKytale, Rua Santiago 30, Castelo Branco, P-6000-179, Portugal

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹JeffA.Berger,²M.E.Schmidt,¹J.L.Campbell,¹E.L.Flannigan,¹R.Gellert,³W.Ming,³R.V.Morris
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113708]
¹University of Guelph, Guelph, Canada
²Brock University, St. Catharines, Canada
³NASA Johnson Space Center, Houston, USA
Copyright Elsevier

The Alpha Particle X-ray Spectrometer (APXS), a field instrument onboard four martian rovers, measures largely unprepared, in situ samples on Mars. The APXS has high precision that enables the determination of elemental concentrations in a wide range of geologic materials. However, lack of sample preparation can lead to heterogeneous matrix effects, and understanding the associated uncertainty is essential for interpreting APXS data. Here we use Particle Induced X-ray Emission spectrometry (PIXE) to analyze a suite of geologic samples from Hawai’i as an analogue study to better understand APXS analyses of martian samples. Wavelength-Dispersive X-ray Fluorescence (WDXRF) analyses of fused glass beads establish higher-accuracy standards for the Hawaiian samples. Sulfate-silicate mixtures were made to evaluate sulfur analysis by PIXE. Results show that the PIXE concentrations for most major elements have 2–6% accuracy, which is comparable to the APXS. However, the PIXE concentrations are systematically high in Al and low in Mg, resulting in lower accuracy (13% and 20%, respectively). Olivine-phyric lavas and most of their altered products have the largest discrepancies with Al concentrations up to 25% high and Mg up to 35% low. Sulfur is systematically high (up to 30% in a basalt matrix) compared to gravimetric S concentrations in the sulfate-silicate mixtures. These systematic deviations in Mg, Al, and S are linked to heterogeneous matrix effects, because PIXE and APXS analyses assume all atoms in a sample to be homogeneously mixed on the sub-micrometer scale, which is not the case. Two key implications for APXS results are: (1) Olivine-bearing samples likely have reported concentrations of Mg that is too low and Al that is too high. Thus, olivine-phyric basalts in Gusev crater and the basaltic sand and soil at three landing sites may have Mg and Al concentrations closer to those of the olivine-phyric shergottites and modelled martian crust than previously thought. (2) Sulfate-silicate mixtures may have overestimated S concentrations reported, resulting in greater uncertainty in the stoichiometry of Ca-sulfates, which is used to deduce the geochemical associations of sulfur in samples.

¹Xiaoqing Xu,^1,2Hejiu Hui,³Wei Chen,⁴Shichun Huang,⁵Clive R.Neal,¹XishengXu
Earth and Planetary Science Letters 536, 116138 Link to Article [https://doi.org/10.1016/j.epsl.2020.116138]
¹State Key Laboratory of Mineral Deposits Research & Lunar and Planetary Science Institute, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
^sCAS Center for Excellence in Comparative Planetology, Hefei 230026, China
³State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Sciences, China University of Geosciences, Wuhan 430074, China
⁴Department of Geoscience, University of Nevada, Las Vegas, NV 89154, United States
⁵Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, United States
Copyright Elsevier

The lunar magma ocean (LMO) model was proposed after the discovery of anorthosite in Apollo 11 samples. However, the chemical and isotopic compositions of lunar anorthosites are not fully consistent with its LMO origin. We have analyzed major and trace elements in anorthositic clasts from ten lunar feldspathic meteorites, which are related to the solidification of the LMO. The plagioclase rare earth element (REE) abundances and patterns are not correlated with the Mg# of coexisting mafic minerals in anorthosites, implying that mafic minerals and plagioclase may not be in chemical equilibrium, consistent with their textural differences. The REE abundances in plagioclase range approximately fortyfold, which cannot be produced by fractional crystallization of a single magma. Combining plagioclase trace element data from Apollo and meteoritic anorthosites, we propose that plagioclases derived from the LMO floated to the surface to form the primordial crust, which then may have been metasomatized by incompatible-element-rich KREEP (potassium, rare earth element, phosphorus) melts and mantle-derived partial melts. The lunar anorthosites may represent this metasomatized crust rather than solely a derivative from the LMO. Furthermore, silicate melts similar to the metasomatic agents may also have melted the crust to form the Mg-suite rocks. This hypothesis is consistent with overlapping ranges of age and initial ε_Nd between lunar anorthosites and Mg-suite rocks. These events are consistent with an overturn event of the cumulate mantle very early after primordial crust formation to produce the partial melts that metasomatized the crust.

¹Vlastimil Vojáček,¹Jiří Borovička,¹Pavel Spurný,¹David Čapek
Planetary and Space Science (in Press) Link to Article [https://doi.org/10.1016/j.pss.2020.104882]
¹Astronomical Institute of the Czech Academy of Sciences, Fričova 298, 251 65, Ondřejov, Czech Republic

We currently do not have a copyright agreement with this publisher and cannot display the abstract here

¹A.Galiano,¹F.Dirri,^1,2E.Palomba,¹ A.Longobardo,³B.Schmitt,³P.Beck
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113692]
¹INAF-IAPS, Rome, Italy
²SSDC-ASI, Rome, Italy
³Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
Copyright Elsevier

The dwarf planet Ceres is an airless body composed of Mg-phyllosilicates, NH₄-phyllosilicates, Mg/Ca-carbonates and a dark component. The subsurface of Ceres, investigated by the material composing the peak of complex craters (ccp, crater central peak material; Galiano et al., 2019), reveals a composition similar to the surface, with an increasing abundance of phyllosilicates in the interior. A moderate trend between age of craters’ formation and spectral slope of ccps suggests that younger ccps show a negative/blue slope and older ccps are characterized by positive/red slope. To investigate the causes of different spectral slope in ccps, different grain-sized Ceres analogue mixtures were produced and spectrally analysed. First, the end-members of the Ceres surface (using the antigorite as Mg-phyllosilicate, the NH₄-montmorillonite as NH₄-phyllosilicate, the dolomite as carbonate and the graphite as dark component), were mixed, obtaining mixtures with different relative abundance, and identifying the mixture with the reflectance spectrum most similar to the average Ceres spectrum. The selected mixture was reproduced with grain size of 0–25 μm, 25–50 μm and 50–100 μm. The three mixtures were heated and spectrally analysed, both with an acquisition temperature of 300 K (room temperature) and 200 K (typical for surface Ceres temperature during VIR observations).

The best analogue Ceres spectrum is coincident with a mixture composed of 18 M% (mass percentage) of Dolomite, 18 M% of Graphite, 36 M% of Antigorite and 28 M% of NH₄-montmorillonite, after experiencing a heating process.

The heating process produces: 1) a darkening and reddening of spectrum, as consequence of the devolatilization of OH group in phyllosilicates and a more dominant effect of opaque phase; 2) a deepening in the intensity of the 3.4 and 4.0 μm band, as well as the 2.7 and the 3.1 μm band, likely due to the loss of absorbed atmospheric water; 3) narrowing of 3.1 μm band and the shift of band center toward longer wavelength (i.e. at 3.06 μm) coincident with mean Ceres spectrum, related to the loss of absorbed atmospheric water.

The analysis of the best Ceres analogue mixture, reproduced at different grain size and after heating process, reveals a weakening of 2.7, 3.1, 3.4 and 4.0 absorption bands in coarser samples, likely related to large size of dark grains which reduce the spectral contrast. Furthermore, spectra of coarser mixtures are more red-sloped, suggesting that this trend is more affected by the dark component.

The best analogue Ceres mixture produced in this work is almost coincident with the mean spectrum of Haulani ccp, the youngest ccps on Ceres and therefore representative of less altered material on Ceres.

The redder spectral slope observed in the older ccps is probably the consequence of the space weathering effects on the original material composing the peak.

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.