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At least 595 records · Page 33

Petrology of Amoeboid Olivine Aggregates in Antarctic CR Chondrites: Evidence for Aqueous Alteration and Shock Metamorphism

CR chondrites are the group of carbonaceous chondrites that preserve records of formation of their components in the solar nebula. Although they are affected by aqueous alteration, many chondrules and CAIs are well-preserved, suggesting they have experienced little thermal metamorphism. We have been investigating the petrologic variations among the CR chondrites in Japanese-NIPR Antarctic meteorite collection. Especially we focused on the petrology of amoeboid olivine aggregates (AOAs) in order to understand secondary alteration on CR chondrite parent body. AOAs are composed of fine-grained forsteritic olivine and refractory minerals formed by condensation from solar nebula, and can be used as sensitive indicators of secondary alteration processes.

Komatsu, M.↗

Stable Carbon Isotopic Signatures of Abiotic Organics from Hydrothermal Synthesis Experiments

Stable carbon isotopes can be powerful biogeochemical markers in the study of life's origins. Biogenic carbon fixation produces organics that are depleted in C-13 by about -20 to -30%0. Less attention has been paid to the isotopic signatures of abiotic processes. The possibility of abiotic processes producing organics with morphologies and isotopic signatures in the biogenic range has been at the center of recent debate over the Earth's earliest microfossils. The abiotic synthesis of organic compounds in hydrothermal environments is one possible source of endogenous organic matter to the prebiotic earth. Simulated hydrothermal settings have been shown to synthesize, among other things, single chain amphiphiles and simple lipids from a mix of CO, CO2, and H2. A key characteristic of these amphiphilic molecules is the ability to self-assemble in aqueous phases into more organized structures called vesicles, which form a selectively permeable boundary and serve the function of containing and concentrating other organic molecules. The ability to form cell like structures also makes these compounds more likely to be mistaken for biogenic. Hydrothermal simulation experiments were conducted from oxalic or formic acid in water at 175 C for 72 hr. The molecular and isotopic composition of the products of these reactions were determined and compared to biogenic fractionations . Preliminary results indicate isotopic fractionation during abiotic hydrocarbon synthesis in hydrothermal environments is on par with biological carbon fixation.

Stern, Jennifer C.↗

Aqueous Alteration and Shock Metamorphism of Antarctic CR Chondrites

CR chondrites are the group of carbonaceous chondrites that best preserve records of formation of their components in the solar nebula. Although they are affected by aqueous alteration, many chondrules and CAIs are well-preserved, suggesting they have experienced little thermal metamorphism. We have been investigating the petrologic variations among the CR chondrites in the NIPR Antarctic meteorite collection. We focused particular attention on the petrology of amoeboid olivine aggregates (AOAs) in order to understand secondary alteration on the CR chondrite parent body. AOAs are composed of fine-grained forsteritic olivine and refractory minerals formed by condensation in the solar nebula, and can be used as sensitive indicators of secondary alteration processes.

Komatsu, M.↗

Mineral-Catalysed Formation of Marine NO and N 2 O on the Anoxic Early Earth

Microbial denitrification converts fixed nitrogen species into gases in extant oceans. However, it is unclear how such transformations occurred within the early nitrogen cycle of the Archean. Here 5we present experimental anoxic surface-catalyzed reduction of nitrite and nitrate via green rust and magnetite combined with diffusion and photochemical modeling. We find that in a Fe 2+ -rich marine environment, Fe minerals could have catalyzed abiotic denitrification reactions leading to the formation of nitric oxide (NO) and nitrous oxide (N 2 O). Nitrate did not exhibit reactivity in the presence of either mineral or aqueous Fe2+, however, both minerals induced rapid nitrite reduction 10to NO and N 2 O. While N 2 O escaped into the atmosphere (63% of nitrite-nitrogen, with green rust as catalyst), NO remained associated with precipitates (7%) serving as a potential shuttle to the benthic ocean.The modeling suggests that marine N 2 O emissions would have sustained 0.8-6 ppb of atmospheric N 2 O without a protective ozone layer. Our findings add detail to the as yet incompletely documented Archean nitrogen cycle, implying a globally distributed process driven 15by chemical kinetics similar to those of modern enzymatically mediated conversions.

Steffen Buessecker↗

Energy yields in the prebiotic synthesis of hydrogen cyanide and formaldehyde

Prebiotic experiments are usually reported in terms of carbon yields, i.e., the yield of product based on the total carbon in the system. These experiments usually involve a large input of energy and are designed to maximize the yields of product. However, large inputs of energy result in multiple activation of the reactants and products. A more realistic prebiotic experiment is to remove the products of the activation step so they are not exposed a second time to the energy source. This is equivalent to transporting the products synthesized in the primitive atmosphere to the ocean, and thereby protecting them from destruction by atmospheric energy sources. Experiments of this type, using lower inputs of energy, give energy yields (moles of products/joule) which can be used to estimate the relative importance of the different energy sources on the primitive earth. Simulated prebiotic atmospheres containing either CH4, CO or CO2 with N2, H2O and variable amounts of H2 were subjected to a high frequency Tesla coil. Samples of the aqueous phase were taken at various time intervals from 1 hr to 7 days, and the energy yields were obtained by extrapolation to zero time. The samples were analyzed for HCN with the cyanide electrode and for H2CO by chromotropic acid. The spark energy was estimated by calorimetry. The temperature rise in an insulated discharge flask was compared with the temperature rise from a resistance heater in the same flask. These results will be compared with calculated production rates of HCN and H2CO from lightning and a number of photochemical processes on the primitive Earth.

Stribling, R.↗

Workshop on Parent-Body and Nebular Modification of Chondritic Materials

Topics considered include: thermal Metamorphosed Antarctic CM and CI Carbonaceous Chondrites in Japanese Collections, and Transformation Processes of Phyllosilicates; use of Oxygen Isotopes to Constrain the Nebular and Asteroidal Modification of Chondritic Materials; effect of Revised Nebular Water Distribution on Enstatite Chondrite Formation; interstellar Hydroxyls in Meteoritic Chondrules: Implications for the Origin of Water in the Inner Solar System; theoretical Models and Experimental Studies of Gas-Grain Chemistry in the Solar Nebula; chemical Alteration of Chondrules on Parent Bodies; thermal Quenching of Silicate Grains in Protostellar Sources; an Experimental Study of Magnetite Formation in the Solar Nebula; the Kaidun Meteorite: Evidence for Pre- and Postaccretionary Aqueous Alteration; a Transmission Electron Microscope Study of the Matrix Mineralogy of the Leoville CV3 (Reduced-Group) Carbonaceous Chondrite: Nebular and Parent-Body Features; rubidium-Strontium Isotopic Systematic of Chondrules from the Antarctic CV Chondrites Yamato 86751 and Yamato 86009: Additional Evidence for Late Parent-Body Modification; oxygen-Fugacity Indicators in Carbonaceous Chondrites: Parent-Body Alteration or High-Temperature Nebular Oxidation; thermodynamic Modeling of Aqueous Alteration in CV Chondrites; asteroidal Modification of C and O Chondrites: Myths and Models; oxygen Fugacity in the Solar Nebular; and the History of Metal and Sulfides in Chondrites.

Zolensky, M. E.↗

What if chondritic porous interplanetary dust particles are not the real McCoy

To select a target comet for a Comet Nucleus Sample Return Mission (CNSRM) it is necessary to have an experimental data base to evaluate the extent of diversity and similarity of comets. For example, the physical properties (e.g., low density) of chondritic porous (CP) interplanetary dust particles (IDPs) are believed to resemble these properties of cometary dust although it is yet to be demonstrated that the porous structure of CP IDPs is inherent to presolar dust particles stored in comet nuclei. Porous structures of IDPs could conceivably form during sublimation at the surface of active comet nuclei. Porous structures are also obtained during annealing of amorphous Mg-SiO smokes which initially forms porous aggregates of olivine + platey tridymite and which, upon continued annealing, react to fluffy enstatite aggregates. It is therefore uncertain that CP IDPs are entirely composed of unmetamorphosed presolar dust. Conceivably, new minerals and textures may form in situ in nuclei of active comets as a function of their individual thermal history. Unmetamorphosed comet dust is probably structurally amorphous. Thermal annealing of this dust can produce ultra fine-grained minerals and this ultrafine grain size of CP IDPs should be considered in assessments of aqueous alterations that could affect presolar dust in comet nuclei between 200 and 400 K. Devitrification and hydration may occur in situ in ice-dust mixtures and the mantle of active comet nuclei. Devitrification, or uncontrolled crystallization, of amorphous precursor dust can produce a range of chemical compositions of ultrafine-grained minerals and (non-equilibrium) mineral assemblages and textures in dust contained in comet nuclei as a function of period and trajectory of orbit and number of perihelion passages (not considering internal heating). Thus, experimental data on relevant processes and reaction rates between 200 and 400 K are needed in order to evaluate comet selection, penetration depth for sampling device and curation of samples for CNSRM.

Rietmeijer, Frans J. M.↗

Acid Vapor Weathering of Apatite and Implications for Mars

Phosphorus is an essential nutrient for terrestrial life, and therefore may be important in characterizing habitability on Mars. In addition, phosphate mobility on Mars has been postulated as an indicator of early aqueous activity [1]. Rock surfaces analyzed by the Spirit Mars Exploration Rover indicate elemental concentrations consistent with the loss of a phosphate-containing mineral [2], and the highly altered Paso Robles deposit contains ~5% P2O5, modeled as 8-10 % phosphate [3]. Depending on the pH of the solution, phosphate can exist as one of four charge states, which can affect its solubility, reactivity and mobility. Phosphate may therefore prove a useful and interesting tracer of alteration conditions on Mars. Acid vapor weathering has been previously studied as a potentially important process on Mars [4-6], and Paso Robles may have been formed by reaction of volcanic vapors with phosphate-bearing rock [3, 7]. Here we present preliminary results of acid vapor reactions in a Parr vessel [6] using fluorapatite, olivine and glass as single phases and in a mixture.

Hausrath, E. M.↗

Alanine synthesis from glyceraldehyde and ammonium ion in aqueous solution

The formation of alanine (ala) form C(14)-glyceraldehyde and ammonium phosphate in the presence or absence of a thiol is reported. At ambient temperature, ala synthesis was six times more rapid in the presence of 3-mercaptopropionic acid than in its absence (0.6 and 0.1 percent, respectively, after 60 days). Similarly, the presence of another thiol, N-acetylcysteinate, increased the production of ala, as well as of lactate. The reaction pathway of thiol-catalyzed synthesis of ala, with the lactic acid formed in a bypath, is suggested. In this, dehydration of glyceraldehyde is followed by the formation of hemithioacetal. In the presence of ammonia, an imine is formed, which eventually yields ala. This pathway is consistent with the observation that the rate ratio of ala/lactate remains constant throughout the process. The fact that the reaction takes place under anaerobic conditions in the presence of H2O and with the low concentrations of simple substrates and catalysts makes it an attractive model prebiotic reaction in the process of molecular evolution.

Weber, A. L.↗

Less-Altered CI Lithology in the Kaidun Meteorite Breccia

One of the most interesting initial results of the characterization of the asteroid Ryugu regolith material returned by the Hayabusa2 spacecraft is the presence of a significant quantity of less-aqueously altered CI material, tentatively called “CI2”. This lithology is characterized by an approximately ten-fold increase in the amount of an hydrous ferromagnesian silicates over what is found n CI1 chondrites, with these being principally olivine, low- and high-calcium pyroxene. Remnant CAI phases are found as well as probable chondrule fragments. Magnetite, pyrrhotite and hydroxyapatite are abundant. The main carbonate is calcite. Matrix is mainly a mixture of saponite and serpentine phases. Assuming that this lithology should be a better representative of the more “primordial” mineralogy of early nebular solids than more processed CI1 material, we have been re-examining CI lithologies found as separate meteorites as well as clasts in other meteorites, seeking similar CI2 material. The Kaidun breccia is notorious for including almost every type of meteorite class except CR2 (which is ironic considering that Kaidun is still officially classified as CR2). We report here the discovery of a probable CI2 lithology in one carbonaceous chondrite-rich Kaidun sample.

Michael Zolensky↗

Acrolein Microspheres Are Bonded To Large-Area Substrates

Reactive cross-linked microspheres produced under influence of ionizing radiation in aqueous solutions of unsaturated aldehydes, such as acrolein, with sodium dodecyl sulfate. Diameters of spheres depend on concentrations of ingredients. If polystyrene, polymethylmethacrylate, or polypropylene object immersed in solution during irradiation, microspheres become attached to surface. Resulting modified surface has grainy coating with reactivity similar to free microspheres. Aldehyde-substituted-functional microspheres react under mild conditions with number of organic reagents and with most proteins. Microsphere-coated macrospheres or films used to immobilize high concentrations of proteins, enzymes, hormones, viruses, cells, and large number of organic compounds. Applications include separation techniques, clinical diagnostic tests, catalytic processes, and battery separators.

Rembaum, Alan↗

The Origin and Evolution of Organic Matter in Carbonaceous Chondrites and Links to Their Parent Bodies

The nature of organic matter in meteorites reveals information about early solar system chemistry and the histories of parent bodies as recorded in the effects of physical and chemical processes that occurred over the past 4.5 billion years. Asteroids and their fragments impact the Earth with approximately 40 million kg of material each year and contributed to the inventory of organics available for the origin of life. Analyses of primitive carbonaceous chondrites over the last five decades have revealed a major insoluble organic component, as well as a complex and highly diverse suite of soluble organic molecules that includes aliphatic and aromatic hydrocarbons, carboxylic acids, hydroxy acids, N-heterocycles, polyols, amino acids, amines, and many other molecules that have not yet been identified. Thermal and aqueous alteration in primitive asteroids played an important role in the formation and destruction organics, including amplification of L-amino acid and D-sugar acid enantiomeric excesses that may have contributed to the origin of homochirality in life on Earth.

Chondrites↗

An integrated view of the chemistry and mineralogy of martian soils

The mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.

Geologic Sediments/chemistry↗

Aqueous Alteration on Mars

The occurrence of extensive valley networks and layered deposits of phyllosilicates and sulfates during the late Noachian/Hesperian periods (approx. 3-4 Gyrs) indicates a past martian climate that was capable of maintaining liquid water at the surface. The planet’s climate drastically changed after these early “episodes” of water to a drier and colder environment during the Amazonian period (past 3.0 Gyrs). The objective of this paper is to describe aqueous alteration/weathering scenarios on Mars based on observations returned by rover and lander missions. The chemistry of most outcrops, rocks, and “soils” that have interacted with water has not been extensively changed from average Mars crustal basaltic composition. Little chemical variation suggests closed hydrologic systems were prominent on early Mars and/or the water/rock ratios were low. Open hydrologic systems occur at local scales, e.g., high Si and Ti rocks and “soil” deposits around a volcanic feature in Gusev crater. Geochemical and mineralogical indicators for aqueous alteration include jarosite and other Fe-sulfates at several locations suggesting acid-sulfate alteration conditions. High Si and Ti rocks, sediments, and “soil” deposits are consistent with basaltic residues extenively leached by extremely acidic fluids. Variations in the Fe/Mn ratio of fracture veins infilled with sulfate-rich materials suggest changes in redox and/or pH conditions of the migrating fluids. The increase of nanophase iron oxides and salts with depth in several “soil” pits escavated by the Spirit rover’s wheel in Gusev crater suggests the translocation/mobolization of these phases by liquid water. This “pedogenic” process is the result of limited water movement through the surface sediments during the Amazonian period; however, it is likely that paleosols exist on Mars that formed during the early “wetter” history of the planet. Soil scientists have the opportunity to continue to (and should) be involved in the exploration of the Red planet.

Ming, Douglas W.↗

An integrated view of the chemistry and mineralogy of Martian soils.

The mineralogical and elemental compositions of the martian soil are indicators of chemical and physical weathering processes. Using data from the Mars Exploration Rovers, we show that bright dust deposits on opposite sides of the planet are part of a global unit and not dominated by the composition of local rocks. Dark soil deposits at both sites have similar basaltic mineralogies, and could reflect either a global component or the general similarity in the compositions of the rocks from which they were derived. Increased levels of bromine are consistent with mobilization of soluble salts by thin films of liquid water, but the presence of olivine in analysed soil samples indicates that the extent of aqueous alteration of soils has been limited. Nickel abundances are enhanced at the immediate surface and indicate that the upper few millimetres of soil could contain up to one per cent meteoritic material.

Zipfel, Jutta↗

The Spatial Distribution of Soluble Organic Matter and Their Relationship to Minerals in the Asteroid (162173) Ryugu

We performed in-situ analysis on a ~1 mm-sized grain A0080 returned by the Hayabusa2 spacecraft from near-Earth asteroid (162173) Ryugu to investigate the relationship of soluble organic matter (SOM) to minerals. Desorption electrospray ionization-high resolution mass spectrometry (DESI-HRMS) imaging mapped more than 200 CHN, CHO, CHO–Na (sodium adducted), and CHNO soluble organic compounds. A heterogeneous spatial distribution was observed for different compound classes of SOM as well as among alkylated homologues on the sample surface. The A0080 sample showed mineralogy more like an Ivuna-type (CI) carbonaceous chondrite than other meteorites. It contained two different lithologies, which are either rich (lithology 1) or poor (lithology 2) in magnetite, pyrrhotite, and dolomite. CHN compounds were more concentrated in lithology 1 than in lithology 2; on the other hand, CHO, CHO–Na, and CHNO compounds were distributed in both lithologies. Such different spatial distribution of SOM is likely the result of interaction of the SOM with minerals, during precipitation of the SOM via fluid activity, or could be due to difference in transportation efficiencies of SOMs in aqueous fluid. Organic-related ions measured by time-of-flight secondary ion mass spectrometry (ToF–SIMS) did not coincide with the spatial distribution revealed by DESI-HRMS imaging. This result may be because the different ionization mechanism between DESI and SIMS, or indicate that the ToF–SIMS data would be mainly derived from methanol-insoluble organic matter in A0080. In the Orgueil meteorite, such relationship between altered minerals and SOM distributions was not observed by DESI-HRMS analysis and field-emission scanning electron microscopy, which would result from differences of SOM formation processes and sequent alteration process on the parent bodies or even on the Earth. Alkylated homologues of CHN compounds were identified in A0080 by DESI-HRMS imaging as observed in the Murchison meteorite, but not from the Orgueil meteorite. These compounds with a large C number were enriched in Murchison fragments with abundant carbonate grains. In contrast, such relationship was not observed in A0080, implying different formation or growth mechanisms for the alkylated CHN compounds by interaction with fluid and minerals on the Murchison parent body and asteroid Ryugu.

Ryugu↗

Extraterrestrial Amino Acids in the C2 Ungrouped Carbonaceous Chondrite Tarda: A Unique Distribution

Introduction: Meteorites provide a record of the chemical processes that occurred in the early solar sys-tem. The delivery of organic matter by carbonaceous chondrites to the early Earth could have been an im-portant source of amino acids and other prebiotic or-ganic molecules required for the emergence of life [1]. To date, 96 amino acids have been named in meteor-ites, most of which are rare or absent in the biosphere [2]. The variability in amino acid concentrations and isomer distributions measured in carbonaceous chon-drites can be explained by differences in parent body chemistry and alteration conditions [3]. In addition, aqueous alteration was likely important in the amplifi-cation of some left-handed amino acids over their right-handed forms (L-excesses up to ~60%) in the Tagish Lake meteorite [3], suggesting that the origin of life on Earth and possibly elsewhere in the solar sys-tem was biased towards L-amino acids. On August 25, 2020, a fireball was witnessed in southern Morocco and the first pieces of the meteorite fall were recovered the following day near the town of Tarda [4]. Thousands of individual fragments were recovered from the strewn field totaling ~4 kg [4]. Based on petrographic observations, bulk mineralogy, and chemical and O-isotopic analyses, Tarda has been classified as a C2 ungrouped carbonaceous chondrite with similarities to Tagish Lake (though more primi-tive), as well as CI, CY, and CR chondrites [4,5]. The fall and rapid recovery of the Tarda stones provide an important opportunity to investigate a C-rich meteorite using the state-of-the-art techniques that will also be used to study the samples returned from asteroids Ryugu and Bennu by the Hayabusa2 and OSIRIS-REx missions, respectively. Here, we report the first amino acid analyses of the Tarda meteorite. The total concentrations, enantio-meric ratios and relative distributions of amino acids were determined using ultrahigh performance liquid chromatography with UV fluorescence and time-of-flight mass spectrometry (LC-FD/ToF-MS) at NASA GSFC. This analytical technique was employed on extracts from two different pre-rain Tarda meteorite fragments and a sample of sand collected from the Tarda fall site for the purpose of assessing potential terrestrial contamination. Bulk H, C, and N elemental and isotopic analyses were also conducted at the Car-negie Institution for Science (CIS) to assist with petro-logic type classification using elemental analysis iso-tope ratio mass spectrometry (EA-IRMS).

D P Glavin↗

Microgravity Compatible Reagentless Instrumentation for Detection of Dissolved Organic Acids and Alcohols in Potable Water

The Organic Acid and Alcohol Monitor (OAAM) program has resulted in the successful development of a computer controlled prototype analyzer capable of accurately determining aqueous organic acids and primary alcohol concentrations over a large dynamic range with high sensitivity. Formic, acetic, and propionic acid were accurately determined at concentrations as low as 5 to 10 micrograms/L in under 20 minutes, or as high as 10 to 20 mg/L in under 30 minutes. Methanol, ethanol, and propanol were determined at concentrations as low as 20 to 100 micrograms/L, or as high as 10 mg/L in under 30 minutes. Importantly for space based application, the OAAM requires no reagents or hazardous chemicals to perform these analyses needing only power, water, and CO2 free purge gas. The OAAM utilized two membrane processes to segregate organic acids from interfering ions. The organic acid concentration was then determined based upon the conductiometric signal. Separation of individual organic acids was accomplished using a chromatographic column. Alcohols are determined in a similar manner after conversion to organic acids by sequential biocatalytic and catalytic oxidation steps. The OAAM was designed to allow the early diagnosis of under performing or failing sub-systems within the Water Recovery System (WRS) baselined for the International Space Station (ISS). To achieve this goal, several new technologies were developed over the course of the OAAM program.

Akse, James R.↗