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At least 163 records · Page 9

Hydrothermal hydration of Martian crust: illustration via geochemical model calculations

If hydrothermal Systems existed on Mars, hydration of crustal rocks may have had the potential to affect the water budget of the planet. We have conducted geochemical model calculations to investigate the relative roles of host rock composition, temperature, water-to-rock ratio, and initial fluid oxygen fugacity on the mineralogy of hydrothermal alteration assemblages, as well as the effectiveness of alteration to store water in the crust as hydrous minerals. In order to place calculations for Mars in perspective, models of hydrothermal alteration of three genetically related Icelandic volcanics (a basalt, andesite, and rhyolite) are presented, together with results for compositions based on SNC meteorite samples (Shergotty and Chassigny). Temperatures from 150 degrees C to 250 degrees C, water-to-rock ratios from 0.1 to 1000, and two initial fluid oxygen fugacities are considered in the models. Model results for water-to-rock ratios less than 10 are emphasized because they are likely to be more applicable to Mars. In accord with studies of low-grade alteration of terrestrial rocks, we find that the major controls on hydrous mineral production are host rock composition and temperature. Over the range of conditions considered, the alteration of Shergotty shows the greatest potential for storing water as hydrous minerals, and the alteration of Icelandic rhyolite has the lowest potential.

NASA Discipline Exobiology↗

Serpentine Nanotubes in CM Chondrites

The CM chondrites are primitive meteorites that formed during the early solar system. Although they retain much of their original physical character, their matrices and fine-grained rims (FGRs) sustained aqueous alteration early in their histories [1- 3]. Serpentine-group minerals are abundant products of such alteration, and information regarding their structures, compositions, and spatial relationships is important for determining the reactions that produced them and the conditions under which they formed. Our recent work on FGRs and matrices of the CM chondrites has revealed new information on the structures and compositions of serpentine-group minerals [4,5] and has provided insights into the evolution of these primitive meteorites. Here we report on serpentine nanotubes from the Mighei and Murchison CM chondrites [6].

Zega, Thomas J.↗

Anorthositic oceanic crust in the Archean Earth

Ultrapure minerals separated from eclogite inclusions in kimberlites were analyzed for Sm, Nd, Sr, and oxygen isotopes and for major and trace elements. Clinopyroxene (cpx) and garnet (gnt) are the only primary mineral phases in these rocks, and mineral phases and their alteration products. The WR sub calc. is the reconstructed bulk composition excluding all the contamination influences. Two groups of eclogites: are distinguished: (1) type A Noritic-anorthositic eclogites; and (2) type B Ti-ferrogabbroic eclogites. The oxygen isotopes are primary mantle-derived features of these rocks and are not caused by posteruption processes, as they were measured on unaltered, clean mineral separates and show a correlation with REE pattern and Sr and Nd isotopes. It is suggested that the variation of the oxygen isotopes are caused by crustal-level fluid-rock interaction at relatively low temperature. It is shown that oxygen isotopes variation in MORB basalts caused by the hydrothermal system are in the same range as the observed oxygen isotope variation in eclogites. A model to explain the new set of data is proposed. It is thought that some of these eclogites might be emplaced into the upper lithosphere or lower crust at the time corresponding to their internal isochron age. The calculated WR composition was used to estimate model ages for these rocks.

Jagoutz, E.↗

The nakhlite meteorites: Augite-rich igneous rocks from Mars

The seven nakhlite meteorites are augite-rich igneous rocks that formed in flows or shallow intrusions of basaltic magma on Mars. They consist of euhedral to subhedral crystals of augite and olivine (to 1 cm long) in fine-grained mesostases. The augite crystals have homogeneous cores of Mg' = 63% and rims that are normally zoned to iron enrichment. The core-rim zoning is cut by iron-enriched zones along fractures and is replaced locally by ferroan low-Ca pyroxene. The core compositions of the olivines vary inversely with the steepness of their rim zoning - sharp rim zoning goes with the most magnesian cores (Mg' = 42%), homogeneous olivines are the most ferroan. The olivine and augite crystals contain multiphase inclusions representing trapped magma. Among the olivine and augite crystals is mesostasis, composed principally of plagioclase and/or glass, with euhedra of titanomagnetite and many minor minerals. Olivine and mesostasis glass are partially replaced by veinlets and patches of iddingsite, a mixture of smectite clays, iron oxy-hydroxides and carbonate minerals. In the mesostasis are rare patches of a salt alteration assemblage: halite, siderite, and anhydrite/ gypsum. The nakhlites are little shocked, but have been affected chemically and biologically by their residence on Earth. Differences among the chemical compositions of the nakhlites can be ascribed mostly to different proportions of augite, olivine, and mesostasis. Compared to common basalts, they are rich in Ca, strongly depleted in Al, and enriched in magmaphile (incompatible) elements, including the LREE. Nakhlites contain little pre-terrestrial organic matter. Oxygen isotope ratios are not terrestrial, and are different in anhydrous silicates and in iddingsite. The alteration assemblages all have heavy oxygen and heavy carbon, while D/H values are extreme and scattered. Igneous sulfur had a solar-system isotopic ratio, but in most minerals was altered to higher and lower values. High precision analyses show mass-independent fractionations of S isotopes. Nitrogen and noble gases are complex and represent three components: two mantle sources (Chas-E and Chas-S), and fractionated Martian atmosphere. The nakhlites are igneous cumulate rocks, formed from basaltic magma at approx.1.3 Ga, containing excess crystals over what would form from pure magma. After accumulation of their augite and olivine crystals, they were affected (to various degrees) by crystallization of the magma, element diffusion among minerals and magma, chemical reactions among minerals and magma, magma movement among the crystals, and post-igneous chemical equilibration. The extent of these modifications varies, from least to greatest, in the order: MIL03346, NWA817, Y000593, Nakhla = Governador Valadares, Lafayette, and NWA998. Chemical, isotopic, and chronologic data confirm that the nakhlites formed on Mars, most likely in thick lava flows or shallow intrusions. Their crystallization ages, referenced to crater count chronologies for Mars, suggest that the nakhlites formed on the large volcanic constructs of Tharsis, Elysium, or Syrtis Major. The nakhlites were suffused with liquid water, probably at approx.620 ma. This water dissolved olivine and mesostasis glass, and deposited iddingsite and salt minerals in their places. The nakhlites were ejected from Mars at approx.10.75Ma by an asteroid impact and fell to Earth within the last 10,000 years. Although the nakhlites are enriched in incompatible elements, their source mantle was strongly depleted. This depletion event was ancient, as the nakhlites source mantle was fractionated while short-lived radionuclides (e.g., t(sub 1/2 = 9 my) were still active. This differentiation event may have been core formation coupled with a magma ocean, as is inferred for the moon.

Treiman, Allan H.↗

Formation of Smectite and Carbonate Minerals From Basaltic Glass on Early Mars

Intense aqueous alteration occurred on early Mars and left behind various secondary minerals. Physicochemical characteristics of ancient aquatic systems are still largely unknown, including why widespread smectite but limited carbonate deposits formed. Acidic events caused by sulfuric acid could permit smectite but inhibit carbonate formation on Mars. Gradual acid neutralization by basalts, however, develops conditions favorable for carbonate precipitation, leading to the coexistence of smectite and carbonates. The objectives of our work were to identify pH conditions and mineralogy of smectite and carbonate formed together from Mars analog basaltic glass.

T. S. Peretyazhko↗

Mechanoregulation of Proliferation, Differentiation, Senescence and Survival of Bone Marrow Primary Osteoprecursor Cells

Cell and animal studies conducted onboard the International Space Station and during the Shuttle program have provided extensive data illustrating bone degenerative responses to mechanical unloading in microgravity. Specifically CDKN1a/p21, an inhibitory modulator of cell cycle progression, is upregulated in osteoprecursor cells of the femur during 15-day spaceflight, suggesting that microgravity can block stem cell-based tissue regenerative process at the level of progenitor proliferation and differentiation. To study a potential role for CDKN1a/p21 in regulating osteogenic mechanosensitivity, we cultured primary bone marrow osteoprogenitor cells from CDKN1a/p21-null (p21-null) and wildtype mice with and without mechanical stimulation, and compared their morphological, proliferative, and in-vitro mineralization responses. Structural cell alterations due to mechanical stimulation were assessed by florescence labeling of f-actin cytoskeleton and focal adhesions. Mechanical stimulation of p21-null cells resulted in more pronounced cytoskeletal alignment with the axis of stretch than for wildtype cells. In addition, p21-null cells subjected to stretch loading also formed significantly more focal adhesions than wildtype cells. Combined these findings suggest that p21-null cells are structurally more responsive to stretch stimulation than the wildtype cells. Because osteoprogenitor cells are well known to respond to mechanical stimulation with increased proliferation, we also tested this response in p21-null cells. Results from those experiments show the proliferative capacity of mechanically stimulated p21-null cells far exceeded that of wildtype controls. Specifically, cell counts from 14, and 21 days post mechanical stimulation, show that p21- null cells to have a 4-fold increase in proliferation compared to wildtype. When the p21-null cell differentiation response to mechanical stimulation was evaluated, the p21-null cultuers elicited more extensive mineralization at earlier assessed timepoints than control cultures. Specifically, Von Kossa staining for mineralized matrix showed that the p21-null cells produced more than twice the mineralized surface area of wildtype cells, and at an earlier 7-day time point in culture. Taken together these results suggest that CDKN1a/p21 normally plays a role in negatively regulating osteoprogenitor proliferation and differentiation responses to mechanostimulation in bone. Findings of CDKN1a/p21's increased expression during spaceflight in microgravity also suggest not only a potential molecular mechanism for arresting regenerative bone growth in space, but potentially also a reduced impact for bone-formation-promoting exercise mechanostimulation. The findings described here constitute a novel role for p21 as a regulator of tissue regeneration in response to mechanical load stimulation, and also suggest a new promising molecular target to promote regenerative health in disuse conditions.

gravity↗

Multispectral Evidence of Alteration from Murray Ridge to Marathon Valley Observed by the Opportunity Pancam on the Rim of Endeavour Crater, Mars

The Mars Exploration Rover Opportunity has been traversing the rim of the Noachian‐aged, 22 km diameter Endeavour crater. Circa sol 3390 of its mission, Opportunity reached the northern tip of the rim segment known as Solander Point and has since been traversing the rim to the south to its current location at the break in the rim known as Marathon Valley. The rocks making up the rim are dominated by impact breccias consisting of clasts and a finer‐grained matrix. Several segments of the rim are transected by fractures as observed from orbital HiRISE imagery. Pancam multispectral observations of outcrop in these fracture regions, including part of the rim crest dubbed Murray Ridge, the Hueytown fracture, and Marathon Valley have been made. Over the range of 430 to 1010 nm there are changes in the multispectral reflectance signature of the breccia matrix with an increase in 535 nm and 904 nm band depth. This is attributed to oxidation and an increase in ferric oxides in these areas. In situ observations by the rover's APXS also indicate chemical differences associated with the matrix along these fractures, including increasing Fe/Mn southward from Solander Point to a region having an Al‐OH signature in CRISM spectra, and generally higher SO3 in the Hueytown fracture region and the area around Spirit of St. Louis. Overturned rocks observed on Murray Ridge were determined by the APXS to have elevated Mn and Pancam spectra of the high Mn spots have a characteristic red, featureless slope. This spectrum was also observed in association with some coatings on blocks of the sulfate‐rich Grasberg formation. Spectra resembling red hematite are observed in some zones in association with the craterform feature Spirit of St. Louis outside the mouth (to the west) of Marathon Valley. Marathon Valley itself has been observed from orbital hyperspectral observations by the CRISM sensor to host occurrences of Fe/Mg smectite minerals‐ indicating extensive aqueous alteration in this region. Pancam observations in Marathon Valley will play an important role in surveying outcrop and making VNIR spectral comparisons with clay bearing outcrop examined earlier in the mission at the Matijevic Hill region.

Farrand, W. H.↗

Stratigraphic Evidence for Early Martian Explosive Volcanism in Arabia Terra

Several large paterae in Arabia Terra are suggested to be calderas that produced colossal explosive eruptions (i.e., supereruptions). If these features are indeed explosive calderas, dispersion modeling suggests extensive ash deposits should be common throughout the region. However, such deposits have not previously been linked with the suggested calderas. Here, we describe layered deposits containing minerals both consistent with and diagnostic of altered volcanic ash throughout Arabia Terra. These deposits include Al-dominant minerals such as montmorillonite, imogolite, and allophane among others. Altered ash deposits are found to thin (from 1-km to 100-m thickness) away from the suggested calderas. We estimate that the volcanic ash observed in Arabia Terra is the result of between 1,000 and 2,000 individual explosive eruptions over 500-million years. Our observations support the hypothesis that Arabia Terra hosted supereruptions in the late Noachian-early Hesperian that repeatedly blanketed the region with layers of ash.

Patrick Whelley↗

Unveiling Clues from Spacecraft Missions to Comets and Asteroids through Impact Experiments

The Deep Impact Spacecraft mission was the first to boldly face the challenge of impacting the surface of a comet, 9P/Tempel 1, to investigate surface and subsurface 'pristine' materials. The Stardust mission to Comet 81P/Wild 2 brought back an exciting surprise: shocked minerals which were likely altered during the comet's lifetime. Signatures of shock in meteorites also suggest that the violent past of the solar system has left our small bodies with signatures of impacts and collisions. These results have led to the question: How have impacts affected the evolutionary path taken by comets and asteroids, and what signatures can be observed? A future planetary mission to a near-Earth asteroid is proposing to take the next steps toward understanding small bodies through impacts. The mission would combine an ESA led AIM (Asteroid Impact Mission) with a JHU/APL led DART (Double Asteroid Redirect Mission) spacecraft to rendezvous with binary near-Earth asteroid 65803 Didymus (1996 G2). DART would impact the smaller asteroid, 'Didymoon' while AIM would characterize the impact and the larger Didymus asteroid. With these missions in mind, a suite of experiments have been conducted at the Experimental Impact Laboratory (EIL) at NASA Johnson Space Center to investigate the effects that collisions may have on comets and asteroids. With the new capability of the vertical gun to cool targets in the chamber through the use of a cold jacket fed by liquid nitrogen, the effects of target temperature have been the focus of recent studies. Mg-rich forsterite and enstatite (orthopyroxene), diopside (monoclinic pyroxene) and magnesite (Mg-rich carbonate) were impacted. Target temperatures ranged from 25 deg to -100 deg, monitored by connecting thermocouples to the target container. Impacted targets were analyzed with a Fourier Transform Infrared Spectrometer (FTIR) and Transmission Electron Microscope (TEM). Here we present the evidence for impact-induced shock in the minerals through both spectra and TEM imaging and compare with unshocked samples.

Lederer, Susan M.↗

Skylab S-192 ratio codes of soil, mineral, and rock spectra for ratio image selection and interpretation

A limited theoretical systems study is made of the Skylab S-192 12-channel multispectral scanner's capabilities for geological remote sensing. Laboratory spectra of rocks, minerals, soils, and some vegetation were used to rank the twelve channels and the best twelve of the 66 possible nonreciprocal spectral ratios according to their ability to discriminate among 17 classes of geological targets. Environmental and instrumental noise sources were ignored. The S-192 should be most useful for discriminating minerals deposited by hydrothermal alteration, weathering, and evaporation. Discrimination of igneous rocks will be difficult. Ratio images are recommended over automatic discrimination methods for those geological targets that can be enhanced by ratio imaging. Ratio codes were found for the twelve highest ranked ratios, for use in selecting the ratio images which will best enhance a target of interest. They can also be searched for false alarm candidates for a given target.

Vincent, R. K.↗

Effective use of principal component analysis with high resolution remote sensing data to delineate hydrothermal alteration and carbonate rocks

Methods of applying principal component (PC) analysis to high resolution remote sensing imagery were examined. Using Airborne Imaging Spectrometer (AIS) data, PC analysis was found to be useful for removing the effects of albedo and noise and for isolating the significant information on argillic alteration, zeolite, and carbonate minerals. An effective technique for using PC analysis using an input the first 16 AIS bands, 7 intermediate bands, and the last 16 AIS bands from the 32 flat field corrected bands between 2048 and 2337 nm. Most of the significant mineralogical information resided in the second PC. PC color composites and density sliced images provided a good mineralogical separation when applied to a AIS data set. Although computer intensive, the advantage of PC analysis is that it employs algorithms which already exist on most image processing systems.

Feldman, Sandra C.↗

Dark matter in the solar system

Many small bodies in the solar system, including planetary satellites, comets, and asteroids, have a surface component consisting at least in part of a very low albedo (0.06 or less) solid substance of neutral or red color in the wavelength region 0.3-2.5 microns. Laboratory spectra of organic residues from meteorites and mixtures with hydrous silicates suggest that complex mixtures of complex organic molecules (kerogens) together with aqueous alteration products of igneous minerals may be the source of the dark matter that is distributed so widely throughout the solar system.

Cruikshank, Dale P.↗

Materials dispersion and biodynamics project research

The Materials Dispersion and Biodynamics Project (MDBP) focuses on dispersion and mixing of various biological materials and the dynamics of cell-to-cell communication and intracellular molecular trafficking in microgravity. Research activities encompass biomedical applications, basic cell biology, biotechnology (products from cells), protein crystal development, ecological life support systems (involving algae and bacteria), drug delivery (microencapsulation), biofilm deposition by living organisms, and hardware development to support living cells on Space Station Freedom (SSF). Project goals are to expand the existing microgravity science database through experiments on sounding rockets, the Shuttle, and COMET program orbiters and to evolve,through current database acquisition and feasibility testing, to more mature and larger-scale commercial operations on SSF. Maximized utilization of SSF for these science applications will mean that service companies will have a role in providing equipment for use by a number of different customers. An example of a potential forerunner of such a service for SSF is the Materials Dispersion Apparatus (MDA) 'mini lab' of Instrumentation Technology Associates, Inc. (ITA) in use on the Shuttle for the Commercial MDAITA Experiments (CMIX) Project. The MDA wells provide the capability for a number of investigators to perform mixing and bioprocessing experiments in space. In the area of human adaptation to microgravity, a significant database has been obtained over the past three decades. Some low-g effects are similar to Earth-based disorders (anemia, osteoporosis, neuromuscular diseases, and immune system disorders). As new information targets potential profit-making processes, services and products from microgravity, commercial space ventures are expected to expand accordingly. Cooperative CCDS research in the above mentioned areas is essential for maturing SSF biotechnology and to ensure U.S. leadership in space technology. Currently, the MDBP conducts collaborative research with investigators at the Rockefeller University, National Cancer Institute, and the Universities of California, Arizona, and Alabama in Birmingham. The growing database from these collaborations provides fundamental information applicable to development of cell products, manipulation of immune cell response, bone cell growth and mineralization, and other processes altered by low-gravity. Contacts with biotechnology and biopharmaceutical companies are being increased to reach uninformed potential SSF users, provide access through the CMDS to interested users for feasibility studies, and to continue active involvement of current participants. We encourage and actively seek participation of private sector companies, and university and government researchers interested in biopharmaceuticals, hardware development and fundamental research in microgravity.

Lewis, Marian L.↗

Preliminary Raman Spectroscopic Survey on a Martian Meteorite - Los Angeles

A Raman survey on a flat-sawn rock slab provides the major mineralogy of martian meteorite Los Angeles. Three unreported accessory minerals and seven terrestrial alteration products and contaminants (organic and inorganic) were also found. Additional information is contained in the original extended abstract.

Wang, A.↗

Column Experiments to Interpret Weathering in Columbia Hills

Phosphate mobility has been postulated as an indicator of early aqueous activity on Mars. In addition, rock surfaces analyzed by the Mars Exploration Rover Spirit are consistent with the loss of a phosphate- containing mineral To interpret phosphate alteration behavior on Mars, we performed column dissolution experiments leaching the primary phases Durango fluorapatite, San Carlos olivine, and basalt glass (Stapafjell Volcano, courtesy of S. Gislason, University of Iceland) [3,4]) with acidic solutions. These phases were chosen to represent quickly dissolving phases likely present in Columbia Hills. Column dissolution experiments are closer to natural dissolution conditions than batch experiments, although they can be difficult to interpret. Acidic solutions were used because the leached layers on the surfaces of these rocks have been interpreted as resulting from acid solutions [5].

Hausrath, E. M.↗

Carbon and Sulfur Isotopic Signatures of Ancient Life and Environment at the Microbial Scale: Neoarchean Shales and Carbonates

An approach to coordinated, spatially resolved, in situ carbon isotope analysis of organic matter and carbonate minerals, and sulfur three- and four-isotope analysis of pyrite with an unprecedented combination of spatial resolution, precision, and accuracy is described. Organic matter and pyrite from eleven rock samples of Neoarchean drill core express nearly the entire range of delta(sup 13)C, delta(sup 34)S, Delta(sup 33)S, and Delta(sup 36)S known from the geologic record, commonly in correlation with morphology, mineralogy, and elemental composition. A new analytical approach (including a set of organic calibration standards) to account for a strong correlation between H/C and instrumental bias in SIMS delta(sup 13)C measurement of organic matter is identified. Small (2-3 microns) organic domains in carbonate matrices are analyzed with sub-permil accuracy and precision. Separate 20- to 50-micron domains of kerogen in a single approx. 0.5 cu cm sample of the approx. 2.7 Ga Tumbiana Formation have delta(sup 13)C = −52.3 +/- 0.1per mille and −34.4 +/- 0.1per mille, likely preserving distinct signatures of methanotrophy and photoautotrophy. Pyrobitumen in the approx. 2.6 Ga Jeerinah Formation and the approx. 2.5 Ga Mount McRae Shale is systematically 13C-enriched relative to co-occurring kerogen, and associations with uraniferous mineral grains suggest radiolytic alteration. A large range in sulfur isotopic compositions (including higher Delta(sup 33)S and more extreme spatial gradients in Delta(sup 33)S and Delta(sup 36)S than any previously reported) are observed in correlation with morphology and associated mineralogy. Changing systematics of delta(sup 34)S, Delta(sup 33)S, and Delta(sup 36)S, previously investigated at the millimeter to centimeter scale using bulk analysis, are shown to occur at the micrometer scale of individual pyrite grains. These results support the emerging view that the dampened signature of mass-independent sulfur isotope fractionation (S-MIF) associated with the Mesoarchean continued into the early Neoarchean, and that the connections between methane and sulfur metabolism affected the production and preservation of S-MIF during the first half of the planet's history.

isotopic signatures↗

The First Returned Samples From A C-Type Asteroid Show Kinship to the Chemically Most Primitive Meteorites

Bulk chemical and isotopic compositions, and mineralogy in the asteroid (162173) Ryugu samples show that Ryugu is mainly composed of materials related to the CI (Ivuna-like) carbonaceous chondrite group. The samples consist predominantly of minerals produced by aqueous alteration in a parent planetesimal from which Ryugu was derived. The 53Mn-53Cr systematics of dolomite suggest that this alteration occurred 5.2 (+0.7/–0.8) million years after formation of Ca-Al-rich inclusions, the first solids formed in the Solar System. The aqueous alteration temperature at the time dolomite and magnetite coprecipitated was 37±10°C. Unlike in CI chondrites, phyllosilicates in Ryugu have lost most of their interlayer water, but retained structural water. This indicates that following aqueous alteration the Ryugu samples avoided heating above ~90°C.

Tetsuya Yokoyama↗