^1,2Lucie Riu,^2,3John Carter,²François Poulet,¹Alejandro Cardesín-Moinelo,¹Patrick Martin
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115537]
¹European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
²Institut d’Astrophysique Spatiale (IAS), Université Paris-Saclay, Orsay, France
³Aix-Marseille Université, CNRS, CNES, LAM, Marseille, France
Copyright Elsevier

Assessing the water content at the surface of Mars is key to understand the history of water and past climate of the planet but it also is very important for future exploration and potential In Situ Resource Utilization (ISRU). Numerous locations on the surface, known to harbor hydrated minerals, have been detected and their mineralogical assemblages quantified. Based on previous analyses resulting from the modelling of OMEGA near-infrared spectra, we evaluated in this paper the amount of water that could still be stored in those hydrated minerals that were previously characterized. Overall, we find that on average at the surface the hydrated silicates are composed of ~5 wt% of water with specific regions with >20 wt% localized in 100 m2 areas, that could present a higher ISRU potential. We find that the global amount of water estimated in hydrated silicates corresponds to ~10−4 Global Equivalent Layer (m) for deposits of 1 m in depth, which represents a lower bound but could still indicate that on the surface the hydrated silicates – as detected by OMEGA (< 1% of the surface) – may not globally be an important sink of water.

^1,2Thorsten Kleine,²Theodor Steller,^1,2Christoph Burkhardt,³Francis Nimmo
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115519]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
Copyright Elsevier

The origin of volatile elements in Mars and whether these elements derive from the inner or outer solar system is unclear. Here we show that Mars exhibits nucleosynthetic zinc (Zn) isotope anomalies similar to those of non‑carbonaceous (NC) but distinct from carbonaceous (CC) meteorites. Like for non-volatile elements, Mars’ Zn isotope composition is intermediate between those of enstatite and ordinary chondrites, demonstrating that Mars acquired volatile elements predominantly from its inner solar system building blocks. The Zn isotope data limit the contribution of CI chondrite-like material to Mars to 4% by mass at most and show that Mars accreted less CC material than Earth. The origin of these disparate CC fractions is unclear, but can place constraints on how and when CC-type material was delivered to the inner solar system.

¹Zachary A. Torrano,²Gregory A. Brennecka,¹Cameron M. Mercer,¹Stephen J. Romaniello,¹Vinai K. Rai,¹Rebekah R. Hines,¹Meenakshi Wadhwa
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.03.018]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, 85287
²Lawrence Livermore National Laboratory, Livermore, CA, 94550
Copyright Elsevier

As the earliest-dated solids in our Solar System, calcium-aluminum-rich inclusions (CAIs) provide a record of their formation environment near the young Sun and hold clues to the formation of planetary-scale isotopic reservoirs in the solar protoplanetary disk. Although CAIs from several CV, CK, CM, CO, and ordinary chondrites have been analyzed previously for their Ti isotopic compositions, CAIs from just three CV chondrites have been analyzed for their Cr isotopic compositions, and only a handful of CAIs have been measured for both their Ti and Cr isotopic compositions. We report mass-independent Ti and Cr isotopic anomalies in several CAIs from CV and CK chondrites; this is the first report of the Cr isotopic composition of a CAI from a CK chondrite. With these additional data, we aim to better constrain the compositional range of CAIs in ε50Ti versus ε54Cr space, thereby facilitating the isotopic characterization of the material inherited by the solar protoplanetary disk and the role of CAIs in the formation of distinct planetary-scale isotopic reservoirs in our early Solar System. The narrow range in isotopic anomalies in CAIs when compared to other early-formed refractory inclusions such as platy hibonite crystals (PLACs) and spinel-hibonite inclusions (SHIBs) suggests that CAIs record the mixing of these precursor materials and the averaging of their larger isotopic anomalies. The isotopic composition of CAIs is therefore likely the result of a combination of factors, including mixing of material inherited from their formation region, heterogeneous carrier phase distribution, and thermal processing in the disk. The ε50Ti and ε54Cr isotopic compositions of CAIs are not correlated, further demonstrating that these isotopic anomalies have different carrier phases. The Ti and Cr isotopic compositions of CAIs additionally show that CAIs alone cannot be responsible for the compositional difference between the non-carbonaceous chondritic (NC) and carbonaceous chondritic (CC) isotopic reservoirs but nevertheless do play a role in the formation of these large-scale isotopic reservoirs in the early Solar System.

^1,2Kaitlyn R. Goss,^2,3Mabel L. Gray,^2,3,4Michael K. Weisberg,^2,3Denton S. Ebel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13962]
¹Department of Geology, Mount Holyoke College, South Hadley, Massachusetts, USA
²Department of Earth and Planetary Sciences, American Museum of Natural History (AMNH), New York, New York, USA
³Department of Earth and Environmental Sciences, City University (CUNY) of New York Graduate Center, New York, New York, USA
⁴Department of Physical Sciences, Kingsborough Community College—CUNY, Brooklyn, New York, USA
Published by arrangement with John Wiley & Sons

We studied a thin section of Lewis Cliff (LEW) 87223, an unusual EL3-related, enstatite chondrite (EC) that has primary and secondary features not observed in other ECs. We studied its metal-rich nodules, possible shock features, and chondrules, eight of which are Al-rich chondrules (ARCs). LEW 87223 has petrologic and compositional features similar to EL3s. Enstatite is the dominant mineral; chondrule boundaries are well defined; Si content of metal (0.5–0.6 wt%) is consistent with typical EL3; it has Cr-bearing troilite, oldhamite, and alabandite; and its O-isotopic composition is similar to other ECs. However, metal abundance in LEW 87223 (~13 vol%) is slightly higher than in other EL3s and its metal nodules are texturally and mineralogically different from other ECs. Both high and low Ni metals are present, and its alabandite has higher Fe (27.8 wt% Fe) than in other EL3s. Silicates appear darkened in plane polarized light, largely due to reduction of Fe from silicate. A remarkable feature of LEW 87223 is the high abundance of ARCs, which contain Ca-rich plagioclase and varying amounts of Na-rich plagioclase along chondrule edges and as veins. This suggests Na metasomatism and the possibility of hydrothermal fluids, potentially related to an impact event. LEW 87223 expands the range of known EC material. It shows that ECs are more diverse and record a wider range of parent body processes than previously known. LEW 87223 is an anomalous EL3, potentially the first member of a new EC group should similar samples be discovered.

¹Sandeepan Dhoundiyal,^1,2Alok Porwal,³C.V. Niveditha,³Guneshwar Thangjam,¹Malcolm Aranha¹, Shivam Kumar,¹Debosmita Paul,¹R. Kalimuthu
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115504]
¹Centre of Studies in Resources Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
²Centre for Exploration Targeting, University of Western Australia, Crawley 6009, Western Australia, Australia
³National Institute of Science Education and Research, HBNI, Bhubaneswar 752050, India
Copyright Elsevier

The algorithms for mapping carbonates from Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) data use the depths of the diagnostic carbonate absorption features at ~2.3 μm and ~ 2.5 μm. However, because the band depths are estimated using fixed shoulder wavelengths, subtle shifts in band centres caused by different cations in the carbonates could result in false negatives for carbonates or false positives for other minerals that have absorption features in a similar wavelength range (eg. phyllosilicates, zeolites). This paper proposes a new algorithm that is based on the following attributes of carbonate spectra in the 2.0 to 3.0 μm range: (1) presence of two diagnostic overtones features around ~2.3 μm and ~2.5 μm; however, these features may show red shift or blue shift depending on the nature of cation(s); (2) the inter band gap between ~2.3 μm and ~2.5 μm carbonate absorption features, which remains relatively constant at ~0.2 μm, even if there is a shift in the absorption features; (3) the contiguity of these two features, that is, carbonate spectra do not show any absorption features in between the above two features. The algorithm also includes a novel geometric continuum removal technique for locating the absorption features. The effectiveness of the algorithm is demonstrated using laboratory spectra, CRISM machine learning toolkit’s mineral dataset, as well as CRISM images. The true positive rate (TPR), true negative rate (TNR) and overall accuracy for the method over the CRISM machine learning toolkit’s mineral dataset are 29%, 87% and 83%, respectively.

Dagmara Oszkiewicz¹ et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115520]
¹Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
Copyright Elsevier

Basaltic V-type asteroids are common in the inner part of the Main Asteroid Belt and much less abundant in the mid and outer parts. They are of scientific interest because they sample crusts and mantles of theoretically plentiful differentiated planetesimals that existed in the Solar System four billion years ago. Some Solar System theories suggest that those objects formed in the terrestrial planet region and were then implanted in the main asteroid belt. In consequence, we should observe a large number of fragments of multiple differentiated planetesimals in the inner Main Belt. That region of the Asteroid Belt is filled with V-type fragments; however, they are difficult to tell apart from typical Vestoids and Vesta fugitives. In this work, we focus on physical and dynamical characterization of V-types in the inner Main-Belt and aim to reconcile those properties with the planetesimal formation and evolution theories.

We conducted an observing campaign over the years 2013–2022 and obtained photometric observations of V-type asteroids located mostly outside the Vesta family at specific locations of the inner Main Belt (the so-called Cells I and II). The total number of partial dense photometric lightcurves obtained in this study was
2910. We were able to model
100 V-types. We further supplement those data with 133 spins of V-types from the DAMIT database and 237 objects derived from Gaia DR3 (Ďurech & Hanuš 2023). We found 78%
11% and 38%
13% retrograde rotators in Cell I and II, respectively. This statistic is remarkably consistent with the numerical simulations of the escape paths of Vesta fugitives that predict 81% retrograde rotators in Cell I and 40% in Cell II after the dynamical integration of 2 Gys. Based on our statistics we conclude that if there are non-Vestoids in the inner main belt, they are likely to be very few. This is consistent with the small fraction of anomalous HED meteorites in meteorite collections, small number of non-Vestoids in the middle and outer Main Belt and points to planetesimal formation location close to the Sun.

S. Sidhu ¹, E.A. Cloutis ¹, P. Mann ¹, D. Applin ¹, T. Hiroi ², K. Mengel ³, T. Kareta ⁴, V. Reddy ⁵, P. Beck ⁶, S.A. Mertzman ⁷
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115522]
¹Centre for Terrestrial and Planetary Exploration, University of Winnipeg, Winnipeg, Manitoba R3B 2E9, Canada
²Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
³Technical University of Clausthal, Clausthal-Zellerfeld 38678, Germany
⁴Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001, USA
⁵Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
⁶Institut de Planétologie et d’Astrophysique de Grenoble, University of Grenoble Alpes, Grenoble 38000, France
⁷Department of Earth and Environment, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604-3003, USA
Copyright Elsevier

Several carbonaceous chondrites (CCs) display evidence of aqueous and thermal alteration. However, the process of thermal alteration is not fully understood. To investigate the spectral variations caused by thermal alteration, we heated powders of CM2 CCs Murchison and Jbilet Winselwan, as well as a simulant Murchison mixture (WMM) and its end members. Heating was conducted up to 1200 °C, in 100 °C increments under a purified nitrogen environment. We also compared the findings of our study with results of previous heating experiments conducted on CCs to better understand the effect differing conditions have on the spectral properties observed. Formation of Fe3+ oxyhydroxides and the decomposition of serpentine due to heating are confirmed by both reflectance and X-ray diffraction (XRD) data. Fe3+ oxyhydroxides features such as a steep slope in between 350 to ~700 nm, and an ~850 nm feature can be seen starting at ~300 and 400 °C, respectively. The serpentine-associated features start to decompose at ~700 °C and disappear by ~900 °C. Spectra >1000 °C are generally dark and featureless and above this temperature, mafic silicate absorption bands begin to appear. Our results show that heating-induced spectral variations are evident, and the nature of these changes depends on various parameters including temperature, experimental conditions, duration of heating, sample grain size, as well as mineralogical changes accompanying heating, and heterogeneity between CCs.

Thorsten Kleine^1,2, Theodor Steller², Christoph Burkhardt^1,2, Francis Nimmo³
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115519]
¹Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
²Institut für Planetologie, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
³Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
Copyright Elsevier

The origin of volatile elements in Mars and whether these elements derive from the inner or outer solar system is unclear. Here we show that Mars exhibits nucleosynthetic zinc (Zn) isotope anomalies similar to those of non‑carbonaceous (NC) but distinct from carbonaceous (CC) meteorites. Like for non-volatile elements, Mars’ Zn isotope composition is intermediate between those of enstatite and ordinary chondrites, demonstrating that Mars acquired volatile elements predominantly from its inner solar system building blocks. The Zn isotope data limit the contribution of CI chondrite-like material to Mars to 4% by mass at most and show that Mars accreted less CC material than Earth. The origin of these disparate CC fractions is unclear, but can place constraints on how and when CC-type material was delivered to the inner solar system.

Zixu Zhao, Jian Chen, Zongcheng Ling, Xuejin Lu, Zexi Li
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115531]
Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, School of Space Science and Physics, Shandong University, Weihai 264209, China
Copyright Elsevier

The timeline of volcanic activity is critical for constraining the thermal evolution of the Moon. The spatial extents of mare basalts, major products of lunar volcanism, have been precisely extracted from LROC (Lunar Reconnaissance Orbiter Camera) image mosaics. With the maria extents newly extracted from LROC mosaics, we found that a large area of mare basalts in the junction of Oceanus Procellarum, Mare Imbrium, Mare Insularum, and Mare Vaporum (the PIV region) has not yet been dated. This study analysed the chronology, composition, and mineralogy of the PIV region, aiming to finish the picture of basaltic volcanism in the Procellarum region, which is a key puzzle of our global geological mapping of the Moon. According to the topographical, spectral, and compositional characteristics, mare units of the PIV region are defined, and the crater size frequency distribution is measured. The primary craters with diameters >0.1 km in the PIV region are measured, and the absolute model ages of basalt units between ~3.78 Ga and ~ 1.71 Ga are derived. Most western PIV basalt units are Eratosthenian-aged, while eastern units mostly formed in the Imbrian period. The spectra of 4965 small impact craters are extracted to interpret the mineral compositions of the PIV basalt units using Chandrayaan-1 Moon Mineralogy Mapper data. Using a Modified Gaussian Model, the reflectance spectra are deconvoluted, and the obtained modal proportions of mafic minerals show low olivine and high low-Ca pyroxene abundances in the eastern PIV region, while the western region features high olivine and calcic pyroxene concentrations. Three episodes of volcanic events occurring in the PIV region are identified. The first (main) occurred at approximately 3.5 Ga (Late Imbrian), with erupted lava flows with less evolved compositions covering most of the PIV area. The peak of volcanic activity in the Eratosthenian period occurred around 2.5 Ga, where mare basalts with moderately evolved compositions and mineralogy were formed. The last major eruption occurred at approximately 1.8 Ga, forming mare basalts with highly evolved compositions.

¹Shaofan Che, ¹Kenneth J. Domanik, ^1,2Thomas J. Zega
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.03.010]
¹Lunar and Planetary Laboratory, University of Arizona, Tucson AZ
²Department of Materials Science and Engineering, University of Arizona, Tucson AZ
Copyright Elsevier

The microstructures and chemistry of secondary feldspars and phosphates in equilibrated ordinary chondrites (OCs) suggest that fluids were involved in the formation of these phases, challenging the conventional view that secondary alteration of equilibrated OCs occur under water-absent conditions. The newly discovered Sidi El Habib 001 (SEH 001), a halite-bearing H5 OC, provides a unique opportunity to further probe the role of fluids during thermal metamorphism on the OC parent bodies. Here we report a petrographic and mineralogic study of SEH 001, with the aim of understanding the origins of halite grains and their implications for the alteration histories of equilibrated OCs. Our investigation reveals a main halite-bearing lithology and a halite-free lithology, both of which show equilibrated textures. Except for halides, no significant textural or compositional differences were observed between halite-bearing and -free lithologies. Halite occurs at all spatial scales in the main lithology and shows clear textures of replacing albitic plagioclase and Cl-apatite. Chlorapatite grains in SEH 001 are Cl-rich and many of them contain elevated amounts of “other” anions.

Our observations suggest that halite grains in SEH 001 formed in situ on the parent body via precipitation from an aqueous fluid. The replacement of plagioclase and Cl-apatite by halite and the equilibrated textures of halite-bearing and halite-free lithologies point to a hydrothermal alteration history where halite formed during advanced thermal metamorphism before the fluid was completely lost. The two lithologies were likely affected by fluids with different Cl concentrations that resulted from heterogeneous distribution of HCl hydrate. Based on comparison to experimental data, halite in SEH 001 could have survived peak metamorphism because of its relatively high thermal stability. Collisional disruption of its original parent body could also facilitate the preservation of halite via release of heat. In the rubble pile model of the OC parent body formation, subsequent accretion of hot fragments into a rubble pile body could have resulted in the blurred boundaries between halite-free and -bearing lithologies now observed in our sample. The occurrence of halite in SEH 001 is clear evidence that aqueous fluids were involved in the alteration of equilibrated OCs.

Combined with previous reports of hydrous minerals (such as phyllosilicates) and other related aqueous products in unequilibrated OCs, our study further suggests that S-type asteroids, the parent bodies of OCs, could be more hydrated than previously thought and might serve as a potential source of water for terrestrial planets in the inner solar system. Nevertheless, whether the proposed hydrothermal history of SEH 001 can be extrapolated to other equilibrated OCs needs to be tested. The in-situ formation origin of halite in SEH 001 contrasts with the exogeneous origin of halite in Monahans (1998) and Zag, suggesting that halites with different origins occurred on the OC parent bodies. The rarity of halite in OCs could be attributed to the heterogeneous distribution of HCl hydrate in the OC parent bodies, although the fragile nature of halite in terrestrial and laboratory environments also increases the likelihood of halite being destroyed in OC samples.