Abstract In the search for life on Mars, understanding the origin of preserved organics is critical. Expected sources include exogenous delivery, endogenous synthesis, and potentially life. Environmental processing by ultraviolet (UV) irradiation can alter these organics, obscuring hallmarks of their origin. To deconvolve these effects, we conducted an experimental study subjecting the Aguas Zarcas (CM2) carbonaceous chondrite to UV–VIS–NIR (200–2500 nm) irradiation under Mars environmental conditions (8.5 mbar pressure, −4 to −7 °C temperature, Mars atmosphere mix of 95.04% CO 2 , 2.59% N 2 , 1.94% Ar, 0.40% O 2 , and 0.03% H 2 O) for 154 sols (days on Mars) equivalent exposure. We measured changes to carboxylic acid abundances and compound‐specific δ 13 C isotopes and bulk carbon, nitrogen, and hydrogen weight percent and isotopes. Compared to unirradiated samples, UV‐exposed samples displayed nearly a twofold increase in total carboxylic acid abundance, due to elevated quantities of formic (C 1 ) and acetic (C 2 ) acids, while indigenous longer‐chained (C 3 –C 6 ) species displayed no change in abundance. Our results suggest that on Mars, UV irradiation of carbonaceous chondrites over short time scales is unlikely to degrade indigenous carboxylic acids and additionally may represent a photochemical synthesis mechanism for producing short‐chain organic acids from meteoritic insoluble organic matter (IOM), meteoritic carbonates, or atmospheric CO 2 precursors.
Abstract How does the energy deposition profile (light curve), deceleration, and penetration depth in Earth's atmosphere depend on asteroid composition and meteorite type? Here, we present the light curve and velocity profile of 75 bolides from camera‐documented meteorite falls. The light curves as a function of altitude generally develop in the following seven phases: Phase (1) an initial rapid brightening; (2) a gradual increase that sometimes shows periodic brightness variations; (3) an onset and rapid increase of brightness until reaching a plateau; (4) a plateau with occasionally chirping brightness oscillations; (5) flares that result in fragments in the meteor wake; (6) an end flare of sometimes different color; and (7) ongoing ablation and fragmentation until dark flight. These seven phases are interpreted as resulting from solid bodies that cause early brightness oscillations from meteoroid spin, a plateau because of melting and reaching melting equilibrium, chirping oscillations due to plasma instabilities, flares due to fragmentations along fractures from dynamic pressure and thermal stress, and an end flare when the surviving back of the meteoroid explodes. This paper discusses the systematics of how the phase heights depend on entry speed, entry angle, initial mass, and meteorite type. The dynamic pressures during the onset of fragmentation and the end flare correlate with the tensile strength of the recovered meteorites. The results have implications for Planetary Defense when anticipating the energy deposition curve of small solid‐body airbursting asteroid impacts like Chelyabinsk .
Abstract We present a comprehensive study of a meteorite collection from the Atacama Desert (Chile), the driest and most climatically stable desert in the world. This collection includes meteorites from three adjacent Dense Collection Areas (DCAs) in the northern part of the Atacama Desert: Calama, Sierra Gorda, and Chug Chug, referred to as the “Calama area.” Within this region (~550 km 2 ), we conducted a systematic search over a 2.5 km 2 zone in the Calama DCA and compared the resulting density to the nonsystematic recovery density in the Calama area. We also present the 36 Cl‐based terrestrial ages of 49 ordinary chondrites selected from the Calama area. The systematic search yielded a meteorite recovery density of 38 meteorites per km 2 (15 meteorites per km 2 for meteorites >20 g), and the collection exhibits a median terrestrial age of 303 ka. Notably, compared with the El Médano and Catalina DCAs, the Calama area is characterized by a lower meteorite density and younger meteorite terrestrial ages, most likely reflecting the region's more humid climate and more dynamic geomorphology due to its proximity to the pre‐Andean range. Our results further show that meteorite weathering is not correlated with terrestrial age but is instead essentially controlled by the initial porosity of the meteorite, itself related to shock stage. Nevertheless, the Calama area still exhibits higher densities and older terrestrial ages than any other hot desert in the world, confirming that the long‐term preservation of meteorites is observed across the entire Atacama Desert.
Abstract Paleomagnetic investigations of pallasites are important for understanding the dynamo histories of their parent bodies and the formation mechanisms of these meteorites themselves. To understand the temporal evolution of pallasite parent‐body dynamos, additional paleomagnetic studies of new meteorites are needed. However, such efforts require a thorough understanding of magnetic carriers and recording properties of pallasites to ensure that any observed remanence reflects primary magnetic records. Here, we investigate olivine grains in the main group Sericho pallasite to evaluate their suitability for paleomagnetic studies. Electron microscopy, combined with rock magnetic analyses, reveals colloidal, euhedral magnetite grains hosted within iron oxide veins (likely goethite) formed during post‐fall aqueous alteration within our Sericho sample. All results indicate that secondary mineral phases dominate the remanence, precluding reliable recovery of primary parent‐body magnetic fields. Our study presents a cautionary tale about how different samples of the same meteorite can experience heterogeneous degrees of weathering, ranging from effectively pristine to so altered that paleomagnetic studies probing parent body processes cannot be conducted. As such, meteorites must be carefully scrutinized on an individual‐sample basis before paleomagnetic studies to ensure high‐fidelity results.
Abstract Carbonaceous chondrites contain phosphorus, whose speciation and thus history remain to be investigated. Phosphorus/sulfur‐bearing assemblages have been reported in carbonaceous CM chondrites, but there is no consensus about their exact compositions and origins. Here, we present submicrometer‐scale investigations by analytical transmission electron microscopy of phosphorus/sulfur‐bearing assemblages from the CM chondrites Murray and Murchison. Results indicate that, in CM chondrites, phosphorus associated with sulfides occurs under distinct oxidation states. In Murray, we identified a pyrrhotite–schreibersite nanocrystalline assemblage associated with carlsbergite and chromite. Its reduced nature and petrographic context are indicative of a nebular formation mechanism, possibly through kamacite sulfidation. In contrast, Murchison contains nanocrystalline pentlandite assemblages associated with carlsbergite and likely with phosphate phases that we interpret as being produced via interactions with an oxidizing fluid under asteroidal conditions. Thermodynamic modeling suggests that such complex assemblages hosting reactive forms of both phosphorus and nitrogen could promote the synthesis of activated phosphate species such as diamidophosphate, an efficient phosphorylation reagent, thereby underscoring their potential prebiotic significance.
Measurements of bulk H, N, and C abundances and isotopic compositions were conducted on (metal-free) aliquots of 12 powdered enstatite chondrite (EC) samples, from both EH and EL chemical groups, and four aubrites. The ECs covered a range of petrologic types, including both falls and finds. To understand the internal H distributions, the H concentrations of individual silicate minerals were analyzed in situ by NanoSIMS in polished thick sections of six of the ECs. Using these data, combined with published data on H carriers and their modal abundances in ECs, we estimate here that the major silicate minerals, matrix, and mesostasis in unequilibrated ECs account for less than 20% of the total H budget. For the metamorphosed E4-6 chondrites, which exhibit a recrystallized matrix and mesostasis, over 99% of the bulk H contents remain unexplained. We attribute the discrepancies between our analyzed bulk H elemental compositions and the bulk H values reconstituted from in situ measurements are attributed to terrestrial contamination, as water adheres to grain boundaries, surfaces, and fractures. Water also reacts with reduced phases, regardless of whether the meteorite is a fall or find. Similar H isotopic compositions for falls and heavily weathered finds are consistent with, but do not require, that the majority of EC H is terrestrial. Attempts to remove organic terrestrial contamination by solvent extractions only served to moderately shift the H, N, and C isotopic compositions. The delta D, delta 15N, and delta 13C values of EC powders are lighter than BSE, although delta D and delta 13C values partially overlap with atmospheric values. Reconstruction of the H budget of an EL-like parent body with an onion-shell structure suggests that such bodies could account for at most a fourth of the bulk silicate Earth's (BSE's) water budget.
Amorphous carbon (alpha C) is found in various extraterrestrial particles, including those thought to originate from the outer Solar System. alpha C can form through two main processes involving C-rich materials: exposure to energetic charged particles and thermal processing. Laboratory analyses can constrain the origin of alpha C in space, as it is not easily detectable through remote sensing. We here investigate the formation of alpha C on the icy surface of Trans-neptunian objects and Oort cloud comets throughout their exposure to energetic ions. We use organic refractory residues (ORRs), which are laboratory simulants of refractory organics in space, obtained from the irradiation (200 keV ions) of various icy mixtures (N2, CO, CH4, CH3OH). As formed ORRs were further irradiated at room temperature (alpha C-ORRs) and analyzed by Raman spectroscopy. Our as formed ORRs do not exhibit alpha C that is in turn detected in alpha C-ORRs. The carbonaceous structure of alpha C-ORRs shows high disorder and dependence on the initial icy composition. Nitrogen-bearing alpha C-ORRs exhibit structural properties similar to some extraterrestrial particles likely originating from icy outer bodies, whereas annealed alpha C-ORRs mimic materials that underwent different degrees of metamorphism. Our findings highlight how Raman characterization of alpha C in extraterrestrial samples serves as a strong analysis tool in providing insights into the evolution of different Solar System objects.
Volatile-rich xenolithic clasts in different types of brecciated meteorites represent unique pristine solar system material. This study investigates the maturity and thermal history of organic matter using Raman spectroscopy and aqueous alteration effects using infrared spectroscopy in the matrix of 15 volatile-rich clasts (C1 and CM-like) present in a polymict eucrite (NWA 7542) and a howardite (Sar & imath;& ccedil;i & ccedil;ek). Most of the studied C1 and CM-like clasts show similar maturity of organic matter as CI chondrites and CM chondrites, respectively. One CM-like clast from the polymict eucrite NWA 7542 shows Raman spectral signatures of heating after aqueous alteration, and another C1 and a CM-like clast from the howardite Sar & imath;& ccedil;i & ccedil;ek exhibit unique Raman spectral properties probably related to differences in accreted precursor organics compared to CI and CM-chondrites. One olivine-rich, unclassified clast has a high concentration of fayalitic olivine in its matrix, similar to oxidized CV chondrites and other features similar to CM- or C2 chondrites. Various evidence shows that this clast was heated up to 700-800 degrees C post aqueous alteration followed by the formation of fayalitic olivine during a metasomatic alteration process. Peak metamorphic temperature (PMT) estimated using different thermometric approaches does not provide reliable data for clasts altered at low temperatures (<200 degrees C).
Abstract Recent evidence from primitive achondrites and achondrites suggests that early‐formed melted planetesimals are depleted in hydrogen relative to the bulk silicate Earth. Nevertheless, evidence from angrites, the lone oxidized group of achondrites investigated to date, suggests that oxidized planetesimals may be H‐rich relative to their reduced counterparts. Additionally, we have limited constraints, derived from a few ungrouped samples, on the H budgets of outer solar system planetesimals that underwent melting. Therefore, in order to provide additional constraints on the H budgets of oxidized and outer solar system planetesimals that experienced melting, we measured the H contents of silicate minerals in brachinite and tafassite group meteorites, respectively. We found that olivine, pyroxene, and plagioclase across both groups are essentially devoid of H (<~2.6 μg/g H 2 O T ; total H as H 2 O equivalents). Based upon the thermal histories of the tafassite and brachinite parent bodies as well as their petrology and mineralogy, we argue that both bodies were essentially anhydrous prior to their disruption. This result is consistent with prior work on primitive achondrites and achondrites and requires that Earth's H budget be accounted for by accretion of thermally primitive materials, such as chondrites, comets, and ices or capture of nebular gas.
Abstract Here we report on the microstructure and chemistry of sulfide minerals returned from asteroid (162173) Ryugu. We identify a unique sulfide population in particle A0016 composed of violarite (FeNi 2 S 4 ), pyrite (FeS 2 ), chalcopyrite (CuFeS 2 ), pyrrhotite (Fe 1‐x S), and pentlandite ([Fe,Ni] 9 S 8 ). Violarite, pyrrhotite, and pyrite reveal evidence of formation from a fluid including porosity, phyllosilicate inclusions, and gaps along grain boundaries due to volume change. Violarite grains are polycrystalline with spatially correlated Ni and Co enrichments and contain pyrrhotite lamellae measuring 100s nanometers across. Pyrite assemblages are polycrystalline with spatially anticorrelated Ni and Co enrichments. In comparison, the chalcopyrite grain is a compositionally homogeneous single crystal spatially associated with rutile (TiO 2 ). The data suggest that particle A0016 experienced multiple generations of fluid flow. The first generation of fluid flow occurred at low temperatures (25 to 100 °C) under alkaline (pH > 8) conditions, leading to the precipitation of pyrrhotite and pentlandite. In comparison, the second generation of fluid flow was acidic (pH < 6.5) and reducing (−0.14 ≤ Eh ≤ −0.36) at elevated temperatures (230 to 300 °C), leading to formation of pyrite, violarite, and chalcopyrite. The elevated temperatures required to produce this sulfide population are consistent with heating from an impact on Ryugu's parent body.
The 40K-K cosmic-ray exposure (CRE) dating system offers a promising method for determining exposure ages of iron meteorites by combining the radioactive cosmogenic 40K with the stable cosmogenic isotopes 39K and 41K. However, earlier applications relied on semi-empirical production models and inconsistent analytical data sets, limiting their reliability. This study presents a comprehensive reassessment of the 40K-K and 4He/21Ne system using state-of-the-art model calculations. Production rates of 39K, 40K, and 41K were simulated with the GEANT4-INCL++6 framework, incorporating updated excitation functions and fully considering depth-dependent shielding effects. The resulting model yields physically robust relationships between K isotopes and noble gas shielding proxies, such as 4He/21Ne. In addition to revisiting the classical approach used by Voshage and co-workers, we introduce two new alternative strategies for calculating CRE ages: a two-component mixing model and a native-K correction approach that mitigates contamination effects. Overall, these developments establish a more accurate and physically consistent framework for future applications of the 40K-K system in cosmochemistry and studies of galactic cosmic rays.
Space weathering significantly alters the optical, chemical, and structural properties of lunar regolith at micro- and nanoscales; yet detailed nanoscale variability within individual soils remains underexplored. Here we apply transmission electron microscopy (TEM) and atom probe tomography to four mineral grains (olivine, ilmenite, and two agglutinitic grains) from mature Apollo 17 soil 79221, characterizing solar wind-induced damage, vesiculation, nanophase Fe formation, and volatile retention with nanometer resolution. Our analyses reveal pronounced heterogeneity in vesicle morphology, nanophase Fe abundance, and volatile content that varies with mineralogy and exposure history. Oxygen depletion near grain surfaces indicates sputtering effects. Beyond confirming nanoscale heterogeneity, our coordinated analyses resolve, by APT, the Fe-depleted halos around npFe0 in mature ilmenite that we previously documented with the same technique in submature Apollo 17 ilmenite. We identify impact-melt quench textures that contribute non-weathering npFe0 to agglutinitic grains, and find a thick damage rim with few npFe0 in Mg-rich olivine accumulates. TEM observations of elongated, linear vesicles aligned parallel to ilmenite blade margins within a bladed agglutinitic grain further suggest crystallographic rather than directional control of vesicles in ilmenite inclusions. We also establish that vesicles distort APT reconstructions and degas during field evaporation, complicating quantitative inventories of npFe0 and volatiles in space-weathered grains.
Hummeln is a simple impact structure located in south-eastern Sweden. It is approximately 1.2 km in diameter and almost completely covered by a lake. Here, we present the first detailed investigation of impactites and mapping of the 164.25 m deep drill core Hummeln-1 with a focus on impact metamorphism and the impact process. We find that the drilling has penetrated a complex sedimentary succession representing syn- to postimpact crater fill. It consists of (from base to top) lithic impact breccia (Unit 1), overlain by diamictite and graywacke with an overall fining upward trend grading from sandy into silty to clayey turbidites (Units 2, 3), and, lastly, suspension dominated marine clays and limestone (Units 4, 5). The crater fill was deposited mostly as gravity slides and sediment gravity flows (debris flows, (hyper)concentrated density flows and turbidity flows), which transported sediment into the crater as a series of fan lobes prograding toward the crater center. We have identified shocked quartz in 12 samples covering the interval of 160.69-56.60 m in the drill core and in samples of polymict and suevitic breccia obtained during fieldwork. Shocked quartz grains dominantly record planar fractures (PFs), with an average of 1.5-3.5 sets per grain. We measured a total of 122 PF sets in 54 grains, with orientations parallel to the , (0001), and orientations being most common (30%, 26%, 21%, respectively). In the same samples, we also measured and indexed 14 sets of planar deformation features (PDFs) in eight grains, oriented parallel to the basal plane (50%), as well as rhombohedral planes , , and (21%, 21%, and 7%, respectively). Feather features occur associated with PFs in seven of the samples. The quartz grains with shock microstructures in the drill core occur exclusively in beige graywacke-diamictite interbedded with the basal lithic breccia unit and in distinct graywacke-diamictite beds in the late syn- to early postimpact crater fill. We suggest that Hummeln was formed just prior to the deposition of parallel bedded marine mudrock with trilobites of the species Ellipsocephalus polytomus, indicating an early "middle" Cambrian (Wuliuan) age for the impact.
Meteorite finds are commonly used to assess the chemical and isotopic compositions of their parent bodies. Among these, lithium (Li) isotopes in ordinary chondrites (OCs) have been applied to infer the Li abundance and isotopic characteristics of their parent bodies. However, Li is highly mobile in aqueous conditions and readily undergoes isotopic fractionation during fluid-mineral interactions. It remains uncertain whether Li isotopic compositions in meteorite finds reliably preserve their original parent-body signatures, particularly after prolonged terrestrial exposure. In this study, we investigated Li isotope behavior in Kumtag 015 (W3, L5) by conducting a series of leaching experiments. The untreated whole-rock sample yields a delta 7Li value of +6.1 parts per thousand, whereas all leachates exhibit heavier delta 7Li values, ranging from +8.4 parts per thousand to +14.8 parts per thousand, indicating the presence of weathering-related secondary components enriched in heavy Li isotopes. Combined with the petrographic observations and mass-balance results, these data suggest that the relatively heavy whole-rock delta 7Li of Kumtag 015 is mainly related to the addition of heavy-delta 7Li surficial fluids during terrestrial weathering, followed by the sequestration of Li into secondary minerals such as carbonates and Fe-(oxyhydr)oxides. This finding is consistent with prior work showing heavy delta 7Li in carbonates. We conclude that terrestrial alteration can substantially modify Li isotope compositions in meteorite finds, highlighting the need for caution when using such samples to trace pristine planetary Li inventories.
Geraisites are a newly recognized class of tektite from Brazil. They occur as centimeter-sized, elongated to subspherical bodies scattered across surface gravel and shallow subsurface layers within a similar to 90-km-long strewn field extending between the municipalities of Sao Joao do Paraiso and Curral de Dentro, near the border between the states of Minas Gerais and Bahia. This study presents a rock magnetic characterization of geraisites, aimed at understanding their magnetic mineralogy and remanent magnetization. The samples exhibit weak bulk magnetization dominated by a paramagnetic contribution, consistent with typical tektite compositions. In addition, rock magnetic analyses indicate the presence of a ferromagnetic fraction, as evidenced by demagnetization curves and hysteresis behavior. Lowrie-Fuller test and isothermal remanent magnetization decomposition indicate a dominant low-coercivity component consistent with nanoscale magnetite grains in the single-domain to pseudo-single-domain range. In some samples, the remanence behavior suggests overprinting by transient high-field processes, such as lightning-induced remanent magnetization. Furthermore, geraisites show a distinct relationship between magnetic susceptibility and iron content compared to other splash-form tektites, reflecting their relatively enhanced ferromagnetic contribution. Overall, these results provide new insights into the magnetic properties of geraisites and their comparison with other tektite populations.
