^1,2,3Phillip Gopon,^3,4James O. Douglas,^3,5Hazel Gardner,³Michael P. Moody,²Bernard Wood,^2,6Alexander N. Halliday,²Jon Wade
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14184]
¹Department of Applied Geosciences and Geophysics, University of Leoben, Leoben, Austria
²Department of Earth Science, University of Oxford, Oxford, UK
³Department of Materials, University of Oxford, Oxford, UK
⁴Department of Materials, Imperial College London, London, UK
⁵Culham Science Centre, UK Atomic Energy Authority, Abingdon, UK
⁶Earth Institute, Columbia University, New York, New York, USA
Published by arrangement with John Wiley & Sons

Millimeter-to-nanometer-sized iron- and nickel-rich metals are ubiquitous on the lunar surface. The proposed origin of these metals falls into two broad classes which should have distinct geochemical signatures—(1) the reduction of iron-bearing minerals or (2) the addition of metals from meteoritic sources. The metals measured here from the Apollo 16 regolith possess low Ni (2–6 wt%) and elevated Ge (80–350 ppm) suggesting a meteoritic origin. However, the measured Ni is lower, and the Ge higher than currently known iron meteorites. In comparison to the low Ni iron meteorites, the even lower Ni and higher Ge contents exhibited by these lunar metals are best explained by impact-driven volatilization and condensation of Ni-poor meteoritic metal during their impact and addition to the lunar surface. The presence of similar, low Ni-bearing metals in Apollo return samples from geographically distant sites suggests that this geochemical signature might not be restricted to just the Apollo 16 locality and that volatility-driven modification of meteoritic metals are a common feature of lunar regolith formation. The possibility of a significant low Ni/high Ge meteoritic component in the lunar regolith, and the observation of chemical fractionation during emplacement, has implications for the interpretation of both lunar remote-sensing data and bulk geochemical data derived from sample return material. Additionally, our observation of predominantly meteoritic sourced metals has implications for the prevalence of meteoritic addition on airless planetary bodies.

^1,2Naoya Imae et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.14178]
¹National Institute of Polar Research (NIPR), Tachikawa, Tokyo, Japan
²The Graduate University for Advanced Studies (SOKENDAI), Tachikawa, Japan
Published by arrangement with John Wiley & Sons

Although CI chondrites are susceptible to terrestrial weathering on Earth, the specific processes are unknown. To elucidate the weathering mechanism, we conduct a laboratory experiment using pristine particles from asteroid Ryugu. Air-exposed particles predominantly develop small-sized euhedral Ca-S-rich grains (0.5–1 μm) on the particle surface and along open cracks. Both transmission electron microscopy and synchrotron-based computed tomography combined with XRD reveal that the grains are hydrous Ca-sulfate. Notably, this phase does not form in vacuum- or nitrogen-stored particles, suggesting this result is due to laboratory weathering. We also compare the Orgueil CI chondrite with the altered Ryugu particles. Due to the weathering of pyrrhotite and dolomite, Orgueil contains a significant amount of gypsum and ferrihydrite. We suggest that mineralogical changes due to terrestrial weathering of particles returned directly from asteroid occur even after a short-time air exposure. Consequently, conducting prompt analyses and ensuring proper storage conditions are crucial, especially to preserve the primordial features of organics and volatiles.

¹KATHERINE DE KLEER,^1,2ERY C. HUGHES,³FRANCIS NIMMO,¹JOHN EILER,⁴AMY E. HOFMANN,^5,6,7STATIA LUSZCZ-COOK,⁸KATHY MANDT
Science 384, 682-687 Link to Article [DOI: 10.1126/science.adj0625]
¹Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
²Earth Structure and Processes, Te Pū Ao | GNS Science, Avalon 5011, Aotearoa New Zealand.
³Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA.
⁴Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
⁵Liberal Studies, New York University, New York, NY 10023, USA.
⁶Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA.
⁷Department of Astrophysics, American Museum of Natural History, New York, NY 10024, USA.
⁸NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA.
Reprinted with permission from AAAS

Jupiter’s moon Io hosts extensive volcanism, driven by tidal heating. The isotopic composition of Io’s inventory of volatile chemical elements, including sulfur and chlorine, reflects its outgassing and mass-loss history and thus records information about its evolution. We used submillimeter observations of Io’s atmosphere to measure sulfur isotopes in gaseous sulfur dioxide and sulfur monoxide, and chlorine isotopes in gaseous sodium chloride and potassium chloride. We find 34S/32S = 0.0595 ± 0.0038 (equivalent to δ34S = +347 ± 86‰), which is highly enriched compared to average Solar System values and indicates that Io has lost 94 to 99% of its available sulfur. Our measurement of 37Cl/35Cl = 0.403 ± 0.028 (δ37Cl = +263 ± 88‰) shows that chlorine is similarly enriched. These results indicate that Io has been volcanically active for most (or all) of its history, with potentially higher outgassing and mass-loss rates at earlier times.

¹Justin Filiberto,²Molly C. McCanta
American Mineralogist 109, 805-813 Link to Article [https://doi.org/10.2138/am-2023-9015]
¹Astromaterials Research and Exploration Science (ARES) Division, NASA Johnson Space Center, Houston, Texas 77058, U.S.A.
²Department of Earth and Planetary Sciences, University of Tennessee at Knoxville, Knoxville, Tennessee 37996, U.S.A.
Copyright: The Mineralogical Society of America

The surface of Venus is in contact with a hot (~470 °C), high pressure (92 bars), and caustic (CO2 with S, but little H2O) atmosphere, which should cause progressive alteration of the crust in the form of sulfate and iron-oxide coatings; however, the exact rate of alteration and mineral species are not well constrained. Different experimental approaches, each with its own limitations, are currently being used to constrain mineralogy and alteration rates. One note is that no experimental approach has been able to fully replicate the necessary conditions and sustain them for a significant length of time. Furthermore, geochemical modeling studies can also constrain surface alteration mineralogy, again with different assumptions and limitations. Here, we review recent geochemical modeling and experimental studies to constrain the state of the art for alteration mineralogy, rate of alteration, open questions about the surface mineralogy of Venus, and what can be constrained before the fleet of missions arrives later this decade.

Combining the new results confirms that basalt on the surface of Venus should react quickly and form coatings of sulfates and iron-oxides; however, the mineralogy and rate of alteration are dependent on physical properties of the protolith (including bulk composition, mineralogy, and crystallinity), as well as atmospheric composition, and surface temperature. Importantly, the geochemical modeling results show that the mineralogy is largely controlled by atmospheric oxygen fugacity, which is not well constrained for the near-surface environment on Venus. Therefore, alteration experiments run over a range of oxygen and sulfur fugacities are needed across a wide range of Venus analog materials with varying mineralogy and crystallinity.

^1,2Andrew B. Foerder,¹Peter A.J. Englert,^3,4Janice L. Bishop,⁵Christian Koeberl,⁶Zachary F.M. Burton,^3,4Shital Patel,⁵Everett K. Gibson
American Mineralogist 109, 682-700 Link to Article [https://doi.org/10.2138/am-2022-8779]
¹Hawai’i Institute of Geophysics and Planetology, University of Hawai’i at Mānoa, Honolulu, Hawai’i 96822-2336, U.S.A.
²Department of Earth, Environmental, and Planetary Sciences, University of Tennessee, Knoxville, Knoxville, TN, 37996-1526, U.S.A.
³SETI Institute, Mountain View, California 94043-5139, U.S.A.
⁴NASA Ames Research Center, Moffet Field, California 94035-1000, U.S.A.
⁵Department of Lithospheric Research, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
⁶Department of Geological Sciences, Stanford University, Stanford, California, 94305, U.S.A.
⁷NASA Johnson Space Center, Houston, Texas 77058-3607, U.S.A.
Copyright: The Mineralogical Society of America

The McMurdo Dry Valleys of Antarctica provide a testbed for alteration processes on Mars due to the cold, arid, and windy conditions. Analysis of three sediment cores collected from Don Juan Basin, Wright Valley, Antarctica, reveals that surface sediment formation is primarily dominated by physical alteration. Chemical alteration occurs sporadically in this region and is frequently indicated by the accumulation of sulfates and Cl-bearing salts. We investigated the effects of physical and chemical alteration in Don Juan Basin by considering major and trace element abundances in the sediments based on depth and location. Our results indicate inversely related chemical- and physical-alteration gradients with proximity to Don Juan Pond where the current center of the pond represents a more chemically altering environment and the perimeter a more physically altering one. Comparing calculated sulfate abundances for Don Juan Basin cores to rock and soil samples taken by the rover Curiosity at Gale crater, we observed that the core from within Don Juan Pond best matches Curiosity soil sulfate abundances.

A new Chemical Index of Alteration equation that adjusts for salt dilution was also applied to the Antarctic cores and Curiosity rocks and soils. Our analysis indicates a significantly higher degree of chemical alteration than originally reported for most Antarctic and martian samples. Our investigation provides evidence for aqueous-based chemical alteration under cold, hyper-arid conditions in Don Juan Basin, Antarctica. Our work also demonstrates the analogous nature of terrestrial microenvironments to similar, local-scale sample sites on Mars, thereby supporting past or present chemical alteration on Mars.

^1,2Oriel A. Humes,³Audrey C. Martin,¹Cristina A. Thomas,¹Joshua P. Emery
The Planetary Science Journal 5, 5 108 Open Access Link to Article [DOI 10.3847/PSJ/ad3a69]
¹Northern Arizona University, Flagstaff, AZ 86011, USA; oriel.humes@tu-braunschweig.de
²Technische Universität Braunschweig, Braunschweig, NI 38106, Germany
³University of Central Florida, Orlando, FL 32816, USA

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

¹P.J.Gasda et al.(>10)
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE007923]
¹Los Alamos National Laboratory, Los Alamos, NM, USA
Published by arrangement with John Wiley & Sons

Manganese has been observed on Mars by the NASA Curiosity rover in a variety of contexts and is an important indicator of redox processes in hydrologic systems on Earth. Within the Murray formation, an ancient primarily fine-grained lacustrine sedimentary deposit in Gale crater, Mars, have observed up to 45× enrichment in manganese and up to 1.5× enrichment in iron within coarser grained bedrock targets compared to the mean Murray sediment composition. This enrichment in manganese coincides with the transition between two stratigraphic units within the Murray: Sutton Island, interpreted as a lake margin environment, and Blunts Point, interpreted as a lake environment. On Earth, lacustrine environments are common locations of manganese precipitation due to highly oxidizing conditions in the lakes. Here, we explore three mechanisms for ferromanganese oxide precipitation at this location: authigenic precipitation from lake water along a lake shore, authigenic precipitation from reduced groundwater discharging through porous sands along a lake shore, and early diagenetic precipitation from groundwater through porous sands. All three scenarios require highly oxidizing conditions and we discuss oxidants that may be responsible for the oxidation and precipitation of manganese oxides. This work has important implications for the habitability of Mars to microbes that could have used Mn redox reactions, owing to its multiple redox states, as an energy source for metabolism.

¹K.Yumoto et al. (>10)
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2024.116122]
¹Department of Earth and Planetary Science, The University of Tokyo, Bunkyo, Tokyo, Japan
Copyright Elsevier

Asteroids (162173) Ryugu and (101955) Bennu observed by Hayabusa2 and Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) share many global properties, but high-spatial-resolution spectral observations by the telescopic Optical Navigation Camera (ONC-T) and MapCam detected subtle but significant differences (e.g., opposite space weathering trends), which may reflect differences in their origin and evolution. Comparing these differences on the same absolute scale is necessary for understanding their causes and obtaining implications for C-complex asteroids. However, ONC-T and MapCam have a large imager-to-imager systematic error of up to 15% caused by the difference in radiometric calibration targets. To resolve this problem, we cross calibrated albedo and colour data between the two instruments using the Moon as the common calibration standard. The images of the Moon taken by ONC-T and MapCam were compared with those simulated using photometry models developed from lunar orbiter data. Our results show that the cross-calibrated reflectance of Ryugu and Bennu can be obtained by upscaling the pre-cross-calibrated reflectance of Bennu by 13.3 ± 1.6% at b band, 13.2 ± 1.5% at v band, 13.6 ± 1.7% at w band, and 14.8 ± 1.8% at x band, while those for Ryugu are kept the same. These factors compensate for the imager-to-imager bias caused by differences in targets used for radiometric calibration and solar irradiance models used for data reduction. Need for such large upscaling underscore the importance of using the cross-calibrated data for accurately comparing the Ryugu and Bennu data. The uncertainty in these factors show that the reflectance of Ryugu and Bennu can be compared with <2% accuracy after applying our results. By applying our cross calibration, the geometric albedo of Bennu became consistent with those observed by ground-based telescopes and the OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS). Our result can be simply applied by multiplying a constant to the publicly available data and enables accurate comparison of the optical spectra of Ryugu and Bennu in future studies.

^1,2R. L. Cheng,^1,2J. R. Michalski,^3,4K. A. Campbell
Journal of Geophyiscal Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE007999]
¹Department of Earth Sciences, The University of Hong Kong, Hong Kong, China
²Laboratory for Space Research, The University of Hong Kong, Hong Kong, China
³School of Environment, The University of Auckland, Auckland, New Zealand
⁴Te Ao Mārama—Centre for Fundamental Inquiry, Faculty of Science, The University of Auckland, Auckland, New Zealand
Published by arrangement with John Wiley & Sons

Siliceous hot spring deposits, or sinters, deposit from hot spring discharge at Earth’s surface and are sites of exceptional preservation of biosignatures. Their macro- and micro-textures are regarded as important evidence of past microbial activities in hydrothermal environments. However, biology mimics do occur, and bona fide microbial textures could be destroyed by subsequent diagenesis or other post-depositional processes. Thus, it is paramount to narrow the search for prospective Martian silica-rich deposits that may contain biosignatures from both orbital and rover-based perspectives. This study investigates hydrothermal deposits in Chile, which are analogs of high-silica deposits discovered in the Gusev crater on Mars, through remote sensing and laboratory analysis. Results indicate that compositional remote sensing based on multispectral data with a high spatial resolution of <4 m/pixel reflects various concentrations of silica, which assisted in identifying the direction of discharged hydrothermal flows from the vent to the apron. Micro-infrared mapping of sinters from similar hydrothermal fields linked spectral features to specific textures revealed by scanning electron microscope and chemical compositions confirmed by electron microprobe analysis, indicating that sinters with no shift in their emissivity minimum in the thermal infrared range were more likely to preserve cellular structures. An instrument for collecting multispectral data with higher spatial resolution could aid in characterizing the geologic settings of potential hot springs on Mars. Locating emissivity minima in the infrared regions of silica that do not shift to a lower position would suggest the potential for well-preserved microbial structures in Martian sinters, if life ever did exist there.

¹Carolyn A. Crow,¹Cynthia Tong,²Timmons M. Erickson,³Desmond E. Moser,¹Aaron S. Bell,⁴Nigel M. Kelly,⁵Tabb C. Prissel
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14162]
¹Department of Geological Sciences, University of Colorado Boulder, Boulder, Colorado, USA
²NASA JSC\Jacobs Technology, Houston, Texas, USA
³Western University, London, Ontario, Canada
⁴Bruker Corporation, Billerica, Massachusetts, USA
⁵NASA JSC, Houston, Texas, USA
Published by arrangement with John Wiley & Sons

Investigations of trapped melt inclusions in minerals can yield insights into the compositions and conditions of parent magmas. These insights are particularly important for detrital grains like many of the lunar zircons found in samples returned by the Apollo missions. However, unlike their terrestrial counterparts, lunar zircons have potentially been exposed to billions of years of impact bombardment. Samples from terrestrial impact structures and impact shock experiments have revealed that deformation during an impact event produces melt and glass blebs that can mimic igneous melt inclusions in both morphology and composition. We have undertaken a geochemical and textural investigation of zircons from Apollo impact melt breccia 14311 to assess their formation mechanisms. The association of trapped melts with shock microtwins and monomineralic melt compositions suggests some inclusions formed as a result of the high pressures and temperatures of impact shock. All other inclusions in this study are associated with curviplanar features, planar features, crystal plastic deformation, or embayments (large regions in contact with adjacent melts or minerals) suggesting that they are not igneous melt inclusions. While these textures can be produced in tectonic environments, impacts are a likely formation mechanism since impacts are the main driver of tectonics on the Moon. The results of this study demonstrate that a combination of textural and compositional analyses can be employed distinguish between igneous melt inclusions and melt blebs in zircons from impact environments.