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.

¹Aaron S. Bell,²Charles Shearer,¹Lydia Pinkham,³Anthony J. Irving
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2023.02.019]
¹Department of Geological Sciences, University of Colorado Boulder
²Institute of Meteoritics and Department of Earth and Planetary Sciences, University of New Mexico
³Department of Earth and Space Sciences, Seattle, WA 98195
Copyright Elsevier

One of the enduring problems in angrite petrogenesis is how to reconcile the extraordinary Fe-rich compositions of many angritic liquids – which seemingly require modestly oxidized fO2 conditions that fall outside the stability field of Fe-Ni alloys during primordial melting – with the geochemical and paleomagnetic evidence that the angrite parent body contains a small metallic Fe-Ni-S-C core. One of the major impediments to resolving these contradictions stems from a distinct lack of rigorous fO2 data for the angrite meteorite clan. To begin addressing this issue, we have developed a new approach for calculating magmatic fO2 values directly from the late-stage olivine-ulvöspinel- silicate liquid assemblages that are common in the volcanic or hypabyssal angrites. The adaptation of the olivine-spinel-oxybarometer for use in angrites requires a careful assessment of
of angritic liquids. We apply the results of metal saturated angrite crystallization experiments and an analysis of the Ca-Tschermak’s-anorthite-equilibrium to obtain estimates of thevalues angritic magmas. We then use the
estimates derived from the experiments and thermodynamic analysis in conjunction with the olivine-spinel-
oxybarometer to calculate the magmatic fO2 of Sahara 99555, D’Orbigny, and Northwest Africa 12004. With this approach we estimate oxygen fugacity values that range from IW+0 to IW+0.25. The relatively reducing fO2 values obtained from our analysis are inconsistent with redox conditions required by the oxidized melting hypothesis. Some caution is warranted in extrapolating these late-stage magmatic fO2 values to higher temperatures; however, we stress that fractionated silicate liquids typically become more oxidized with increasing crystallization via auto-oxidation (i.e., the accumulation of incompatible ferric iron in the liquid). Therefore, we suggest that late stage magmatic fO2 values from our calculations may represent the most oxidized conditions along the angrite liquid line of descent. If this interpretation is correct, a large-scale oxidation event on the APB need not be invoked to reconcile mildly reducing conditions (ΔIW-1.35) thought to have prevailed during core formation with the magmatic fO2 record preserved in angritic meteorites. Future redox studies of compositionally primitive angrites (e.g., Northwest Africa 12774) may shed new light on the redox relationships among primitive angrite magmas, evolved angrite magmas, and core forming alloys.

¹Emerson J. Speyerer,¹Mark S. Robinson,¹Aaron Boyd,¹Victor H. Silva,²Samuel Lawrence
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115506]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85282, United States of America
²NASA Lyndon B. Johnson Space Center, Houston, TX 77058, United States of America
Copyright Elsevier

The Ultraviolet/Visible (UVVIS) camera on the Clementine spacecraft provided a global, multispectral view of the Moon. Scientists commonly use individual observations and derived products (optical maturity, mineral abundance, etc.) over 25 years later, addressing questions concerning the composition and relative age of surface features. However, since the mission concluded, our knowledge of lunar topography and the locations of features on the surface have improved with results from the Lunar Reconnaissance Orbiter (LRO) and Gravity Recovery and Interior Laboratory (GRAIL) missions. Before this work, cross-mission comparisons were impaired by spatial offsets between the derived products, which are as large as 2.5 km in some regions. Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) images, acquired under similar lighting conditions, were used as a cartographic reference. We used image-based feature-matching algorithms to automatically derive control points to improve the positional accuracy of each UVVIS observation with the LROC WAC basemap. From ground control points, we calculate a precise camera model (focal length, optical distortion, etc.) for the UVVIS camera and update the pointing for each UVVIS image. Using the updated geometric information and projecting the UVVIS image to the LOLA global shape model, we map the five-band multispectral UVVIS mosaic, the optical maturity map, and FeO and TiO2 abundance maps. We also analyze pitch observations of the polar regions to investigate the influence phase angle has on the derived optical maturity. The new images are registered to the GRAIL-based LRO geodetic framework within a WAC pixel (Ground Sampling Distance ~75 m; average UVVIS sigma0 = 0.084), creating a foundational geospatial data product that does not require any manual interpretation or nonlinear warping of map products to align with the current lunar reference frame.

¹Liang Zhang,²Xubing Zhang,¹Maosheng Yang,¹Xiao Xiao,³Denggao Qiu,³Jianguo Yan,¹Long Xiao,^1,2Jun Huang
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2023.115505]
¹State Key Laboratory of planetary processes and mineral resources, School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
²School of Geography and Information Engineering, China University of Geosciences, Wuhan 430078, China
³State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430070, China
⁴Chinese Academy of Sciences Center for Excellence in Comparative Planetology, Hefei 230026, China
Copyright Elsevier

In the past, global maps of major oxides and magnesium number (Mg #) on the lunar surface had been derived from spectral data of remote sensing images, combined with “ground truth” geochemical information from Apollo and Luna samples. These compositional maps provide insights into the chemical variations of different geologic units, revealing the regional and global geologic evolution. In this study, we produced new maps of five major oxides (i.e., Al2O3, CaO, FeO, MgO, and TiO2) and Mg # using imaging spectral data from the KAGUYA multiband imager (MI) and the one-dimensional convolutional neural network (1D-CNN) algorithm. We took advantage of recently acquired geochemical information from China’s Chang’E-5 (CE-5) samples. We used the coefficients of determination (R2) and Root Mean Squared Error (RMSE) as model evaluation indicators. We compared the results with the models used by Wang et al. (2021) and Xia et al. (2019). Our study shows that the 1D-CNN algorithm model used in this study had a higher degree of fit and smaller dispersion between the “ground truth” value of geochemical information and the predicted value of spectral data. The 1D-CNN algorithm generally performs better in describing the complex nonlinear relationship between spectra and chemical components. In addition, we present regions of mare domes in Mairan Dome (43.76°N, 49.90°W) and irregular mare patches (IMPs) in Sosigenes (8.34°N, 19.07°E) to demonstrate the geologic implications of these new maps. With the highest spatial resolution (~ 59 m/pixel), these new maps of five major oxides and Mg # will serve as an important guide in future studies of lunar geology.

¹Ming Ma,¹Jingran Chen,²Clive R. Neal,^3,4Shengbo Chen,¹Bingze Li,¹Chenghao Han,¹Peng Tian
Icarus (in Press) LinktoArticle [https://doi.org/10.1016/j.icarus.2023.115464]
¹School of Surveying and Exploration Engineering, Jilin Jianzhu University, Changchun, China
²Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
³School of Geo-Exploration Science and Techniques, Jilin University, Changchun, China
⁴Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
Copyright Elsevier

High alumina (HA) mare basalts play unique roles in understanding the heterogeneity of lunar mantle. Their presence was confirmed by the Apollo and Luna samples, and their remote sensing identification was implemented using HA sample FeO, TiO2 and Th concentration constraints. This study selected the surfaces with ~0.5% rock abundance as windows into HA basalts identification. The lithology of these rock pixels was first classified based on thorium maps from the Lunar Prospector and major element oxide products from Diviner data onboard the Lunar Reconnaissance Orbiter (LRO). Then, the LRO Diviner Al2O3 (~11 wt%) concentration constraint was applied in the mare basalt rock pixels across the Moon. The mare-highland mixtures were distinguished from HA basalt rocks based on the positive linear relationships between Al2O3 and Mg# in the adjacent pixels for four impact vector directions away from each candidate HA pixel. These HA basalts rock pixels identified by this study indicate that HA basalts are concentrated locally in South Pole-Aitken (SPA) basin, Schiller-Schickard region and 13 maria such as southern and northern Oceanus Procellarum, central Humorum, Tranquillitatis, Fecunditatis and Serenitatis, northern Imbrium and southern Nubium, but are seldom found in Mare Moscoviense and Orientale regions on the farside. Detailed investigations in Mare Fecunditatis found that fifteen HA basalt units or patches could be confidently identified. These HA basalts have the total area and volume of <77,658 km2 and < 54,301 km3, and the maximum depth and thickness of 1147 m and 1062 m respectively. In addition, analyses of the HA rocks indicated that the HA basalts are discontinuous and have variable thicknesses.

^1,2Razvan Caracas,³Sarah T. Stewart
Earth and Planetary Science Letters 608, 118014 Link to Article [https://doi.org/10.1016/j.epsl.2023.118014]
¹Université Paris Cité, Institut de Physique du Globe de Paris, CNRS, 1 rue Jussieu, Paris, 75005, France
²The Center for Earth Evolution and Dynamics, University of Oslo, Oslo, 0371, Norway
³Department of Earth and Planetary Sciences, University of California, Academic Surge, 1124 Crocker Ln, Davis, 95616, CA, USA
Copyright Elsevier

Vaporization is a major outcome of giant impacts during planet formation. The last giant impact marked a major stage in the early history of our planet, with the formation of a highly vaporized protolunar disk, that condenses onto the final Earth and Moon. The thermodynamic state of the disk and its condensation path are still uncertain, as most impact simulations have not used accurate material models. In this study, we compute the critical point and liquid spinodal of the bulk silicate Earth composition. We find that the thermal profiles through portions of the protolunar disk and the post-impact Earth exceeded the mantle critical point of 80-130 MPa kbars and 6500-7000 K. We find that Earth, and most rocky planets, will traverse a temporary state that lacks a surface defined by a magma ocean-atmosphere boundary. Furthermore, the atomic structure of the silicate fluid varies with the radius within the disk due to strong pressure and temperature gradients. Fluffy short-lived chemical species dominate the outer parts of the disk, and long-lasting dense polymers abound in the deeper parts. During cooling, the silicate vapor condenses and the composition of the post-impact atmosphere is dominated by species along the mantle vapor curve.