¹R. Christoffersen,²M. J. Loeffler,^1,3S. Kanee,⁴C. J. Cline II,⁴L. P. Keller,¹T. M. Erickson,^5,6J. Fontanese,⁷T. Munsat,^5,6M. Horányi
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2025JE009257]
¹Amentum, NASA Johnson Space Center, Houston, TX, USA,
²Department of Astronomy and Planetary Science, NorthernArizona University, Flagstaff, AZ, USA,
³Now at Department of Earth & Environment, Boston University, Boston, MA,USA,
⁴NASA Johnson Space Center, Houston, TX, USA,
⁵Laboratory for Atmospheric and Space Physics, University ofColorado, Boulder, CO, USA,
⁶NASA SSERVI’s Institute for Modeling Plasma, Atmospheres and Cosmic Dust(IMPACT), University of Colorado, Boulder, CO, USA,
⁷Department of Physics, University of Colorado, Boulder,CO, USA
Published by arrangement with John Wiley & Sons

The flux of solar system meteoroids is dominated by objects less than 1 mm in diameter whose impact effects play a major role in the space weathering of airless body surfaces. These effects remain poorly characterized with respect to their dependence on the range of impact speeds for meteoroids across the inner solar system. We investigated this dependence specifically for the mineral olivine using an electrostatic dust accelerator to bombard olivine single crystals with a stream of Fe metal dust particles traveling at measured speeds between 0.3 and 20 km s⁻¹. The impacting particles produced microcraters 0.2–5.2 μm in diameter whose content of impact melt, and brittle/ductile shock-induced deformation features, were characterized by scanning and transmission electron microscopy. While particles traveling <1 km s⁻¹ were not able to form microcraters, analysis of the size versus speed relations for the faster particles allowed their impact speeds and maximum shock pressures to be statistically constrained. Microcraters 0.2–0.5 μm in diameter contain olivine-composition shock melt estimated to have formed at impact speeds as high as 15–20 km s⁻¹, and shock pressures more than 250 GPa. Transmission electron microscope studies of shock melt in larger, ∼1.5 μm diameter, microcraters found it was free of impact-generated nanophase metallic Fe (npFe⁰). The impact speeds for these craters of 3.0–5.0 km s⁻¹ suggest that in asteroid regoliths dominated by olivine, still higher impact speeds may be necessary to allow npFe⁰ to be produced.

¹F. Alberquilla et al. (>10)
Journal of Geophysical Research: Planets 131, e2025JE009515 Open Access Link to Article [https://doi.org/10.1029/2025JE009515]
¹IBeA Research Group (Ikerkuntza eta Berrikuntza Analitikoa ‐ Analytical Research and Innovation), Department ofAnalytical Chemistry, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Leioa, Spain
Published by arrangement with John Wiley & Sons

The study of terrestrial lava tubes is essential for understanding geological processes occurring during volcanic activity on other planetary bodies, such as Mars. These processes lead to the formation of minerals analogous to those found on other planets. Volcanic eruptions are often associated with hydrothermal activity and gas emissions (e.g., CO2, SO2, H2S, HCl, H2O, H2) through fumaroles, which can simulate Martian atmospheric conditions. These gases and fluids interact with the host rock, leading to mineral alteration and the formation of secondary minerals. This study analyzes the Cueva del Vidrio lava tube on La Palma (Canary Islands, Spain), formed during the 1949 San Juan eruption. Although its materials exhibit low alteration due to their relatively recent origin, the 2021 Tajogaite eruption introduced new gas emissions, groundwater interactions, and surface runoff, thereby promoting the formation of alteration crusts and coatings. The methodology combined minimally invasive techniques, such as X-ray diffraction, and non-destructive techniques, including X-ray fluorescence (μEDXRF) and Raman spectroscopy. In order to facilitate the interpretation of the results, runoff waters were analyzed by ion chromatography. The results highlight the presence of carbonates, sulfates, and iron oxides, notably hematite, which likely formed from silicate weathering, particularly olivine alteration, leading to iron depletion and magnesium enrichment. Additionally, amorphous silica was identified, likely formed through reactions involving sulfate and carbonate precipitation, which leached silicon from silicate-rich host rocks. Similar processes have been described on Mars, where opal is considered a key mineral for astrobiological investigations due to its potential for preserving biosignatures.

¹Mehmet Yesiltas,²Andrew Dopilka,²Robert Kostecki,¹Timothy D. Glotch,¹Paul Northrup
Proceedings of the National Academy of Sciences of the USA (PNAS) 123, e2601891123 Link to Article [https://doi.org/10.1073/pnas.2601891123]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY 11794
²Energy Technologies and Systems Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Asteroid Bennu preserves primitive material from the early solar system, and returned samples allow direct examination of how organics and minerals were assembled and altered. We applied nanoscale infrared spectroscopy together with Raman spectroscopy to the Bennu sample OREX-800066-3 to characterize chemical variability at ~20 nm scales. Analysis of nano-Fourier-transform infrared spectroscopy spectra identifies three recurring compositional domains; aliphatic-rich, carbonate-rich, and nitrogen-bearing organic-rich regions. Statistical evaluation shows that these domains are compositionally and spatially distinct at the nanoscale, with strong negative correlations between aliphatic signatures and both carbonates and N-bearing organics, and negligible correlation between carbonates and N-bearing organics. Organosulfur compounds are spatially restricted to carbonate-rich regions, indicating organic-sulfate interactions during late-stage brine evolution. Raman spectra indicate highly disordered, thermally minimally metamorphosed carbonaceous matter, consistent with preservation of labile functional groups. These results demonstrate that Bennu’s angular lithology (characterized by planar facets and sharp edges) is not chemically uniform and records heterogeneous aqueous alteration rather than pervasive uniform processing. N-bearing organic functional groups are widely preserved despite extensive alteration, and carbonate-rich areas show intimate nanoscale mixing of different carbonate species. The coexistence of distinct organic- and carbonate-rich domains suggests contributions from both primordial compositional diversity and subsequent rock–fluid interaction. Comparison with Ryugu samples highlights shared features but key differences in organic-carbonate associations and carbonate distributions. Overall, Bennu’s nanoscale heterogeneity provides constraints on organic preservation, carbonate formation, organic-sulfate chemistry, and parent-body evolution in volatile-rich early solar system materials.

¹Thomas M. McCollom,²Sally L. Potter-McIntyre,¹Andres Reyes,³Bruce Moskowitz,³Peter Solheid,⁴Victoria E. Hamilton
Jpurnal of Geophysical Research: Planets Link to Article [https://doi.org/10.1029/2025JE009489]
¹Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO, USA
²Southern Illinois University, Carbondale, IL, USA
³Department of Earth and Environmental Sciences and Institute for Rock Magnetism, University of Minnesota, Minneapolis, MN, USA
⁴Southwest Research Institute, Boulder, CO, USA
Published by arrangement with John Wiley & Sons

A key early discovery of the Mars Exploration Rover Opportunity on Meridiani Planum was the hematite spherules that are a ubiquitous component of the Burns formation sandstones at the rover’s landing site (colloquially known as “blueberries”). The Meridiani spherules possess a suite of characteristics that are collectively very rare in terrestrial settings, including their gray color, a thermal spectral signature that indicates preferential exposure of the c crystal axis, a spherical shape that is evidently attributable to radially oriented crystallite growth, and high chemical and mineralogical purity. The origin of the Meridiani “blueberries” has remained a matter of considerable debate, but one leading hypothesis is that they formed through the decomposition of iron-rich sulfate minerals from the alunite group, specifically jarosite. To date, however, there has been no described terrestrial analog where the formation of hematite spherules is shown to be directly linked to jarosite decomposition. Here, we report the discovery of hematite spherules in Aztec Sandstone that possess many of the same characteristics as the martian “blueberries,” albeit with substantially smaller size. The spherules occur primarily in narrow gray bands within mineralized fractures where the pore spaces are predominantly occupied by jarosite-alunite solid solutions (JASS). The spherules formed through partial decomposition and release of Fe³⁺ from adjacent JASS, supporting the possibility that analogous processes may have been responsible for the formation of hematite spherules during diagenesis of the sulfate-rich Burns sandstones on Mars. Continued study of the Aztec Sandstone spherules may provide new constraints on near-surface environmental conditions on early Mars.

^1,2Marina E. Gemma,³Katherine A. Shirley,¹Timothy D. Glotch,^2,4,5Denton S. Ebel,^2,5,6Kieren T. Howard
Journal of Geopyhsical Research: Planets (in Press) Link to Article [https://doi.org/10.1029/2025JE008963]
¹Department of Geosciences, Stony Brook University, Stony Brook, NY, USA
²Department of Earth and PlanetarySciences, American Museum of Natural History, New York, NY, USA,
³Atmospheric, Oceanic, and Planetary Physics,University of Oxford, Oxford, UK
⁴Lamont‐Doherty Earth Observatory, Columbia University, Palisades, NY, USA
⁵Department of Earth and Environmental Sciences, Graduate Center of the City University of New York, New York, NY,USA
⁶Department of Physical Sciences, Kingsborough College, City University of New York, Brooklyn, NY, USA
Published by arrangement with John Wiley & Sons

aboratory spectral analysis of well-characterized meteorite samples can be employed to more quantitatively analyze asteroid remote sensing data in conjunction with returned extraterrestrial samples. In this work, we examine the combined effects of physical (temperature, particle size) and chemical (petrologic type, metal fraction) variables on visible and near-infrared (VNIR) spectra of ordinary chondrite meteorite powders. Six equilibrated ordinary chondrite meteorite falls were prepared at a variety of particle sizes to capture the spectral diversity associated with asteroid regoliths dominated by various grain sizes. Mineral compositions and abundance were determined from electron microprobe analysis of meteorite thick sections to precisely characterize changes in spectral features due to variations in mineralogy. VNIR spectra of the ordinary chondrites were measured under simulated asteroid surface conditions at a series of temperatures chosen to mimic near-Earth asteroid surfaces. The resulting spectra show minimal variation in both major absorption bands across the simulated near-Earth asteroid temperature regime. Changes in particle size result in variations in band centers and band area ratios for material of the same composition, two key parameters typically used to derive asteroid composition. Unlike previous spectral investigations of ordinary chondrites, we retained the metal fraction in our powders instead of analyzing only the silicate fraction. Metal has a subtle but non-negligible effect on the VNIR spectra of ordinary chondrites. The more petrologically pristine samples from each ordinary chondrite group display relatively weaker absorption bands than their more thermally altered counterparts. The band centers shift to longer wavelengths as grain size and petrologic type increase.

¹S. P. Aithala,¹R. A. Lange,¹M. M. Hirschmann
Journal of Geophysical Research: Planets (in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009148]
¹Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, USA, 2Department ofEarth and Environmental Sciences, University of Michigan, Ann Arbor, MI, USA
Published by arrangement with John Wiley & Sons

To elucidate the relationship between oxygen fugacities (f_O2) recorded in martian basalts and redox processes in the martian interior, superliquidus 100-kPa furnace experiments on a composition similar to Humphrey (Adirondack basalt) were conducted at variable f_O2 and temperature. Quenched glasses were analyzed by EPMA, Mössbauer spectroscopy, colorimetric wet chemistry, and microbeam X-ray absorption near edge structure (XANES) spectroscopy. The experiments reveal Mössbauer and wet chemical determinations of silicate glass Fe³⁺/Fe^T agreeing within uncertainty, supporting the accuracy of extended-Voigt-based fitting of Mössbauer spectra when recoil-free fraction is considered. Fe³⁺/Fe^T ratios determined from Mössbauer spectroscopy from Humphrey and previously studied martian-relevant glass compositions are combined to calibrate models that characterize the relationship between Fe³⁺/Fe^T, f_O2, temperature, and composition in martian silicate liquids. The models demonstrate, similar to previously investigated silicate liquids, that the correlation between $$ and log f_O2 in martian magmas has a slope less than the value (0.25) expected if ferric and ferrous iron oxide mixed ideally. Martian magma Fe³⁺/Fe^T ratios are more temperature-sensitive compared to non-martian compositions, suggesting that temperature variations may contribute to comparatively large f_O2 variations in martian basalt. The models are applied to demonstrate that the Fe³⁺/Fe^T increases required to explain multiple-log unit changes in f_O2 in shergottite magma would not increase terrestrial magma f_O2 as effectively. To aid in future investigations of martian magma redox, a XANES technique that allows for non-destructive, microanalytical characterization of Fe³⁺/Fe^T in natural martian materials and martian-relevant experiments is introduced.

¹Megan Broussardet al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701381]
¹Department of Earth, Environmental, and Planetary Sciences and the McDonnell Center for the Space Sciences,Washington University in St. Louis, St. Louis, Missouri, USA
Published by arrangement with John Wiley & Sons

CI chondrites are a compositionally primitive group of meteorites that haveundergone extensive aqueous alteration, providing insights into the evolution of primitiveplanetesimals. Oued Chebeika 002 is the most pristine CI chondrite to date. In this work,we report its mineralogy, bulk chemistry, oxygen and potassium isotope ratios, andcosmogenic radionuclides 10 Be, 26 Al, and 36 Cl. The 10 Be cosmic ray exposure ages of OuedChebeika 002 samples are 2.6 0.5 and 2.9 0.7 Myr. The d41 K of two samples is0.114 0.019 and 0.247 0.044 &. We find that the mineralogy, oxygen isotopes,potassium isotopes, and bulk chemistry of Oued Chebeika 002 overlap with those ofsamples returned from the asteroids Ryugu and Bennu. We therefore propose that CI chondrites and the asteroids Bennu and Ryugu may have originated from a common parentbody, for which we propose the name “Naunet,” after an Egyptian goddess of primordialwater. Naunet formed in the outer solar system and underwent aqueous alteration. In themain belt, Naunet broke up, producing rubble-pile asteroids, including Bennu, Ryugu, andthe secondary CI chondrite parent body/bodies, fragments of which survived passage to theEarth’s surface, becoming CI chondrites.

¹Tetsuya Yokoyama et al. (>10)
Meteoritics & Planetary Science (in Press) Open Access Link to Article [doi: 10.1111/maps.701411]
¹Department of Earth & Planetary Sciences, Institute of Science Tokyo, Meguro, Japan
Published by arrangement with John Wiley & Sons

Sample return missions play a significant role in planetary science by providing
pristine extraterrestrial materials. JAXA’s Hayabusa2 and NASA’s OSIRIS-REx missions
have returned samples from the C-type asteroids Ryugu and Bennu, respectively. The
chemical and mineralogical compositions of these samples closely resemble those of CI
chondrites, the traditional reference material for solar system abundances. Based on the
findings of the Hayabusa2 mission, JAXA launched the Ryugu Reference Project (RRP) to
maximize the scientific value of the returned samples and formed the RRP Measurement
Definition Team (RRP-MDT) to elucidate the RRP’s scientific goal and objectives. The
RRP-MDT defined the goal of RRP to reassess the elemental abundances and isotopic
compositions of the solar system through comprehensive analyses of the returned asteroid
samples and CI chondrites. To this end, the team recommended preparing homogeneously
powdered Ryugu reference materials (RRM) using approximately 750 and 400mg of
samples from Chambers A and C, respectively, to address observed compositional
heterogeneities. The team proposed to measure the elemental abundances and isotopic
compositions of the RRM by analytical techniques involving seven specific measurement
groups. Through comprehensive analytical methodologies, interlaboratory calibration, and
statistical evaluation, the RRP aims to refine our understanding of solar system formation
and evolution

^1,2Anna E. Engle, ³Helen E. Maynard-Casely, ^2,1Jennifer Hanley, ³Christopher Baldwin
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117069]
¹Northern Arizona University, Flagstaff, 86011, AZ, USA
²Lowell Observatory, Flagstaff, 86001, AZ, USA
³Australian Centre for Neutron Scattering, ANSTO, Kirrawee DC, 2232, NSW, Australia
Copyright Elsevier

Ethane (CH), propane (CH), and butane (CH₁₀) are present on many outer solar system bodies but our understanding of their solid phase behaviors is still limited. Linear alkanes are known to exhibit multiple solid phases, with at least one of them being a disordered crystalline phase, wherein the molecules remain in a structured placement but have a freedom of rotation about one or multiple axes. Elucidating the properties of these solid phases is critical for understanding the geochemical and geomorphological processes occurring on icy bodies, thus we undertook an investigation of these three simple alkanes at temperatures relevant to the outer solar system via neutron diffraction. We report on extracted thermal expansion properties, observed phase behaviors, and subsequent analysis of their ’loosely packed’ crystal structures through calculations of crystal voids, contact parameters, and fingerprint plots.

^1,2,3Christopher J. Barnes,⁴Aleksander Błasiak,⁵Helge Vinje Birgerheim,⁵Matthias Konrad-Schmolke,⁵Delia Rösel,^3,4Jarosław Majka,⁵Thomas Zack
Meteoritics & Planetary Science (in Press) Open Access Link to Article [https://doi.org/10.1111/maps.70137]
¹Institute of Geological Sciences, Polish Academy of Sciences, Krakow, Poland
²Department of Earth and Environmental Sciences, University of British Columbia Okanagan, Kelowna, British Columbia,Canada
³Department of Earth Sciences, Uppsala University, Uppsala, Sweden
⁴Faculty of Geology, Geophysics & Environmental Protection, AGH University of Krakow, Krakow, Poland
⁵Department of Earth Sciences, University of Gothenburg, Gothenburg, Sweden
Published by arrangement with John Wiley & Sons

The mineralogy and textures of several fragments from the Ribbeck aubrite were analyzed using a combination of scanning electron microscopy, electron microprobe analysis, μRaman spectroscopy, and laser ablation inductively coupled reaction cell mass spectrometry (LA-ICP-MS/MS). The meteorite fragments are strongly brecciated and show evidence of shock melting. The silicate phases of the fragments predominantly consist of enstatite, albite, and roedderite, with subordinate forsterite, diopside, K-feldspar. Non-silicate phases include kamacite, troilite, oldhamite, and Fe-Ti, Fe-Mn, and Fe-Cr rich sulfides. Tridymite and cristobalite, the latter contained in Si-rich glass, are also present within one enstatite grain. Vesicular fusion crust is apparent in several fragments. The discovery of roedderite is the first reported for the Ribbeck aubrite. In situ Rb/Sr dating combined with chemical analysis of the roedderite was performed via laser ablation ICP-MS/MS using the single-spot dating approach. The average chemistry of 20 roedderite analyses is 68.7 wt% of SiO2, 23.1 wt% of MgO, 4.9 wt% of K2O, and 3.3 wt% of Na2O and is <0.1 wt% of FeO. The total concentrations of Rb and Sr are 282 and <1 μg g−1, respectively. Single-spot Rb/Sr dates from the same 20 analyses yielded a weighted average of 4570 ± 27 Ma, interpreted as the formation age of the Ribbeck aubrite parent body. The result highlights advantages of single-spot Rb/Sr dating compared to short-lived isotopic systems (e.g., 26Al-26Mg, 53Mn-53Cr, and 129I-129Xe), long-lived systems with radiogenic noble gasses (e.g., 40K-40Ar and 238/235U-232Th-4He), and the conventional Rb/Sr isochron approach for meteorite cosmochronology.