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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Bronzite Granophyre: New insight on Vredefort

The Vredefort Dome is located near the center of the Witwatersrand Basin, about 120 km southeast of Johannesburg, South Africa. Its origin is enigmatic, ranging from a major impact event to endogenous processes, either igneous or tectonic. A unique melt rock, the 'Bronzite' Granophyr, occurs in the Vredefort structure as vertical ring dikes along the contact between sedimentary collar and core of Archaean granites, and as vertical dikes extending northwest-southeast and northeast-southwest in the granitic core. The granophyre rocks have an unusual composition and high content of recrystallized sedimentary inclusions compared to common intrusive igneous rocks with similar SiO2 content (61 to 70 percent by weight). The unique nature of the granophyre has been underlined in previous studies and origin hypotheses as an impact melt or as a highly contaminated intrusive mafic magma have also been discussed. We present new results obtained from a recent detailed petrographic and geochemical study of a very large and texturally diverse suite of 'Bronzite' Granophyre, representing all dikes occurring at Vredefort.

Therriault, A. M.↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 12

Topics discussed include: The Ancient Lakes in Hellas Basin Region as Seen Through the First Year of Mars Express HRSC-Camera; DISR Observations of Craters at Titan at the Huygens Landing Site: Insights Anticipated; The Sun s Dust Disk - Discovery Potential of the New Horizons Mission During Interplanetary Cruise; Evidence for Aqueously Precipitated Sulfates in Northeast Meridiani Using THEMIS and TES Data; Integrated Spectroscopic Studies of Anhydrous Sulfate Minerals; Venusian Channel Formation as a Subsurface Process; Reexamination of Quartz Grains from the Permian-Triassic Boundary Section at Graphite Peak, Antarctica; Observations of Calcium Sulfate Deposits at High Latitudes by OMEGA/Mex at Km/Pixel Resolutions; Observations of the North Permanent Cap of Mars in Mid-Summer by OMEGA/MEX at km per Pixel Resolutions; Classification and Distribution of Patterned Ground in the Southern Hemisphere of Mars Genesis: Removing Contamination from Sample Collectors; Thermal Characterization of Fe3O4 Nanoparticles Formed from Poorly Crystalline Siderite; Hydrogen Abundances in Metal Grains from the Hammadah Al Hamra (HaH) 237 Metal-rich Chondrite: A Test of the Nebular-Formation Theory; REE and Some Other Trace Elements Distributions of Mineral Separates in Atlanta (EL6); The Composition and Origin of the Dewar Geochemical Anomaly; Asteroid Modal Mineralogy Using Hapke Mixing Models: Testing the Utility of Spectral Lookup Tables; and The Huygens Mission at Titan: Results Highlights. (sup 182)Hf-(sup 182)W Chronometry and an Early Differentiation in the Parent Body of Ureilites Ground Penetrating Radar in Sedimentary Rocks Mars, Always Cold, Sometimes Wet: New Constraints on Mars Denudation Rates and Climate Evolution from Analog Studies at Haughton Crater, Devon Island, High Arctic Europa s Porous Ice Rheology and Implications for Ice-penetrating Radar Scattering Loss Surface Generated Cracks on Europa

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NASA NTRS2012

Antarctic Mirabilite Mounds as Mars Analogs: The Lewis Cliffs Ice Tongue Revisited

It has been proposed, based on geomorphic and geochemical arguments, that subsurface water has played an important role in the history of water on the planet Mars [1]. Subsurface water, if present, could provide a protected and long lived environment for potential life. Discovery of gullies [2] and recurring slopes [3] on Mars suggest the potential for subsurface liquid water or brines. Recent attention has also focused on small (< approx. 1km dia.) mound-like geomorphic features discovered within the mid to high latitudes on the surface of Mars which may be caused by eruptions of subsurface fluids [4, 5]. We have identified massive but highly localized Na-sulfate deposits (mirabilite mounds, Na2SO4 .10H2O) that may be derived from subsurface fluids and may provide insight into the processes associated with subsurface fluids on Mars. The mounds are found on the end moraine of the Lewis Cliffs Ice Tongue (LCIT) [6] in the Transantarctic Mountains, Antarctica, and are potential terrestrial analogs for mounds observed on the martian surface. The following characteristics distinguish LCIT evaporite mounds from other evaporite mounds found in Antarctic coastal environments and/or the McMurdo Dry Valleys: (1) much greater distance from the open ocean (approx.500 km); (2) higher elevation (approx.2200 meters); and (3) colder average annual temperature (average annual temperature = -30 C for LCIT [7] vs. 20 C at sea level in the McMurdo region [8]. Furthermore, the recent detection of subsurface water ice (inferred as debris-covered glacial ice) by the Mars Reconnaissance Orbiter [9] supports the use of an Antarctic glacial environment, particularly with respect to the mirabilite deposits described in this work, as an ideal terrestrial analog for understanding the geochemistry associated with near-surface martian processes. S and O isotopic compositions.

Socki, Richard A.↗
NASA NTRS2009

Robotic Recon for Human Exploration

Robotic reconnaissance has the potential to significantly improve scientific and technical return from lunar surface exploration. In particular, robotic recon may increase crew productivity and reduce operational risk for exploration. However, additional research, development and field-testing is needed to mature robot and ground control systems, refine operational protocols, and specify detailed requirements. When the new lunar surface campaign begins around 2020, and before permanent outposts are established, humans will initially be on the Moon less than 10% of the time. During the 90% of time between crew visits, robots will be available to perform surface operations under ground control. Understanding how robotic systems can best address surface science needs, therefore, becomes a central issue Prior to surface missions, lunar orbiters (LRO, Kaguya, Chandrayyan-1, etc.) will map the Moon. These orbital missions will provide numerous types of maps: visible photography, topographic, mineralogical and geochemical distributions, etc. However, remote sensing data will not be of sufficient resolution, lighting, nor view angle, to fully optimize pre-human exploration planning, e.g., crew traverses for field geology and geophysics. Thus, it is important to acquire supplemental and complementary surface data. Robotic recon can obtain such data, using robot-mounted instruments to scout the surface and subsurface at resolutions and at viewpoints not achievable from orbit. This data can then be used to select locations for detailed field activity and prioritize targets to improve crew productivity. Surface data can also help identify and assess terrain hazards, and evaluate alternate routes to reduce operational risk. Robotic recon could be done months in advance, or be part of a continuing planning process during human missions.

Deans, Matthew↗
NASA NTRS1994

The role of chondrules in nebular fractionations of volatiles and other elements

For at least 30 years, cosmochemists have been grappling with the question of how and why groups of geochemically and volatility related elements became fractionated in the major chondrite groups. At least five relatively independent fractionations are known. Virtually everyone who has thought about these facts has been attempted to attribute at least some of the fractionations to the physical separation or mixing of the visible components. By far the most abundant of these components in meteorites is chondrules, and indeed chondrules have long been suspected of playing a direct role in fractionation of volatile elements. The question addressed here is whether chondrules formed before or after chemical components became separated is of fundamental importance to our understanding of the early solar system, as the answer constrains how, when, where, and from what chondrules formed, and tells us about how materials were processed in the nebula.

Grossman, J. N.↗
NASA NTRS2007

Mars Sulfate Formation Sourced in Sulfide-Enriched Subsurface Fluids: The Rio Tinto Model

The extensive evidence for sulfate deposits on Mars provided by analyses of MER and Mars Express data shows that the sulfur played an essential role in the geochemical cycles of the planet, including reservoirs in the atmosphere, hydro-sphere and geosphere. Overall the data are consistent with a fluvial/lacustrine-evaporative origin of at least some of the sulfate deposits, with mineral precipitation through oversaturation of salty acidic fluids enriched in sulfates. This scenario requires reservoirs of sulfur and associated cations, as well as an acidic and oxidizing hydrochemistry which could be provided by surface and subsurface catching of meteoric waters resulting in the presence of sulfur-bearing gases and steam photochemistry. In this work we suggest a new scenario for the extensive generation of sulfates in Mars based on the observation of seasonal changes in the redox and pH of subsurface waters enriched in sulfur that supply the acidic Mars process analog of Rio Tinto. This model considers the long-term subsurface storage of sulfur during most of Noachian and its release from the late Noachian to Hesperian time through weathering by meteoric fluids that would acidify and oxidize the sulfur bearing compounds stored in the subsurface.

Fernandez-Remolar, D. C.↗
NASA NTRSDate not supplied

Warm-Based Glacial Landforms and Past Climate Signals: Icelandic Eskers as Proxies for Small Sinuous Ridges on Mars

The surface of Mars exhibits plentiful geomorphic evidence for glacial processes, but the history of the cryosphere on Mars remains debated [e.g., 1, 2]. Recent hydrological modeling predicts that warm-based ice sheets on Mars may have resulted in subglacial incised channels (e.g., valley networks) and eskers [3]. Evidence on Mars for warm-based glaciation includes candidate moraines, bedrock channels, and candidate eskers [e.g., 4-6]. Eskers are sinuous ridges comprising glaciofluvial sediments deposited by meltwater flowing through tunnels at the bed of warm-based large glaciers [e.g., 7, 8]. They provide direct evidence of basal melting of ice and preserve glaciofluvial sediments. Warm-based glacial transport is primarily driven by meltwater and can chemically weather the underlying bedrock. An alternative signature of past climate on Mars may thus be the geochemical record, due to alteration by interactions with glacial meltwater, preserved in esker sediments and strata. At present, the sedimentology and stratigraphy of terrestrial eskers is poorly understood. This study will combine sedimentology, geochemistry, and geomorphology to better constrain the unique properties of eskers resulting from warm-based glaciation on Mars-like substrates by leveraging a natural laboratory in Iceland.

A. M. Rutledge↗
DOE OSTI2022

Sulfur cycling at natural hydrocarbon and sulfur seeps in Santa Paula Creek, CA

Biogeochemical cycling of sulfur is relatively understudied in terrestrial environments compared to marine environments. However, the comparative ease of access, observation, and sampling of terrestrial settings can expand our understanding of organisms and processes important in the modern sulfur cycle. Furthermore, these sites may allow for the discovery of useful process analogs for ancient sulfur-metabolizing microbial communities at times in Earth's past when atmospheric O 2 concentrations were lower and sulfide was more prevalent in Earth surface environments. Here, we identified a new site at Santa Paula Creek (SPC) in Ventura County, CA—a remarkable freshwater, gravel-bedded mountain stream charged with a range of oxidized and reduced sulfur species and heavy hydrocarbons from the emergence of subsurface fluids within the underlying sulfur- and organic-rich Miocene-age Monterey Formation. SPC hosts a suite of morphologically distinct microbial biofacies that form in association with the naturally occurring hydrocarbon seeps and sulfur springs. We characterized the geology, stream geochemistry, and microbial facies and diversity of the Santa Paula Creek ecosystem. Using geochemical analyses and 16S rRNA gene sequencing, we found that SPC supports a dynamic sulfur cycle that is largely driven by sulfide-oxidizing microbial taxa, with contributions from smaller populations of sulfate-reducing and sulfur-disproportionating taxa. This preliminary characterization of SPC revealed an intriguing site in which to study geological and geochemical controls on microbial community composition and to expand our understanding of sulfur cycling in terrestrial environments.

58 GEOSCIENCES↗
NASA NTRS2020

Clay Sediments from Basaltic Terrains: Implications for Sedimentary Processes on Mars

The Mars Science Laboratory (MSL) rover, Curiosity, has been traversing across fluvial, lacustrine, and eolian sedimentary rocks since it touched down in 2012. The CheMin X-ray diffractometer (XRD) on board Curiosity has revealed smectite clay minerals in most fluvio-lacustrine samples and abundant X-ray amorphous materials in all samples analyzed to date. For example, mudstones from the Sheepbed member at the base of the stratigraphic section and the lower part of the Murray formation contain on average ~7 to 20 wt% smectite and ~30 to 46 wt% X-ray amorphous abundances. On Earth, smectite and secondary X-ray amorphous materials are juvenile weathering products that are generated in sedimentary environments and ultimately record the interaction between primary igneous minerals and the hydrosphere, atmosphere, and biosphere. For this study, we investigated glacio-fluvio-eolian sediments generated in basaltic terrains as terrestrial analogs for the mudstones from Gale Crater, Mars. This work focuses on the clay sized sediments (<2 μm) from these deposits as this grain size hosts the most mineralogically and geochemically altered detritus in sedimentary environments. The goal of investigating basaltic sedimentation is to create a terrestrial reference frame that sheds light on the paleoclimate and paleoaqueous conditions responsible for shaping the ancient sedimentary environments of Mars (e.g., Gale Crater and Jezero Crater).

Thorpe, M. T.↗
DOE OSTI2022

Natural colloids facilitated transport of steroidal estrogens in saturated porous media: Mechanism and processes

Steroid estrogens (SEs) are widely distributed in terrestrial environment, whilst the transport of SEs in groundwater is not well understood. Specifically, the effects of ubiquitous natural colloids on the SEs transport are unclear. Here, the influence of inorganic colloids (i.e. silica and illite) and organic colloids, i.e. Humic acid (HA), on the transport of estrone (E1) and estradiol (E2) in saturated porous media were studied in laboratory scale column experiments. Characterization on the colloids and the column packing material was conducted to provide bases for the interpretation of column test findings. Results showed that the transport of SEs was facilitated by the nature colloids that were migrating through the saturated porous media. About 38.5% of E1 and 24.6% of E2 were retained in the column when colloids were absent in the system. Further, when transporting with silica colloids, illite colloids, and HA colloids, the transport of E1 was enhanced by 15.64%, 11.17%, and 25.60%, respectively; whilst the transport of E2 was improved by 19.56%, 23.06%, and 36.40%, respectively. The colloids’ SEs transport enhancement depended not only on the mobility of the colloids but also on their geochemical characteristics. The tested organic colloids showed 1.5-2.5 times greater ability on promoting the transport of SEs than the inorganic ones. The proposed mechanisms of nature colloids facilitated transport of SEs include competing for adsorption sites on the sand surfaces by the colloids resulting mobilization of adsorbed SEs from solid matrix, and transport of colloids as carriers for SEs.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Impacts: Observations and Experiments

The title in this section include: 1) Impactites of the Haughton Impact Structure, Devon Island, Nunavut, Canada; 2) Geochemical Characteristics of Impactites from the Yaxcopoil-1 ICDP Drill Core, Chicxulub Impact Structure, Mexico; 3) Investigation of the Ries Impact Crater Based upon Old and New Geophysical Data and Numerical Modeling; 4) Potential of Radar Imaging and Sounding Methods in Mapping Heavily Eroded Impact Craters: Mapping Some Structural Elements of the Hico Crater, TX; 5) From Simple to Complex Craters: The Mechanics of Late-time Crater Adjustments; 6) Impact Structures: What Does Crater Diameter Mean? 7) Early-Time Temperature Evolution of the Impact Flash and Beyond; 8) Probing Impact-Generated Vapor Plumes; 9) Non-Ballistic Vapor-Driven Ejecta; 10) Depth and Diameter of Transient Craters; 11) A Plausibility of Z-Model; 12) Experiments with Explosives and Ordnance Disposal Devices for the Simulation of Specific Processes During Shallow-Marine Impacts; 13) Collisional Fragmentation of Rotating Bodies.

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NASA NTRSDate not supplied

Center for Isotope Cosmochemistry and Geochronology at NASA Johnson Space Center

The Center for Isotope Cosmochemistry and Geochronology (CICG) at the NASA Johnson Space Center, led by Justin Simon, applies novel elemental and isotopic analytical techniques to understand solar system formation, from processes occurring during the earliest Solar Nebula, to the evolution of planetary bodies during planet formation and differentiation. CICG consists of an integrated suite of labs including dedicated spaces for specialized handling and preparation of meteorites and planetary return samples, metal-free clean chemistry, and mass spectrometry. In addition to a Thermo-Scientific Triton thermal ionization mass spectrometer (TIMS) for high precision isotopic analyses in processed samples, CICG houses two additional mass spectrometry instruments with added laser ablation capabilities for high spatial resolution in-situ measurements: (1) a Thermo-Scientific Element-XR inductively coupled mass spectrometer (ICP-MS) with a Teledyne Photon Machines Analyte Excite+ laser ablation system, and (2) a Nu Sapphire 1700 multi-collector ICP-MS, a large geometry instrument with a multi-pole collision cell for interference removal, with an Applied Spectra J200 tandem laser induced breakdown spectroscopy (LIBS) femto-second laser ablation system. We detail the analytical capabilities of CICG in the context of current and future research projects related to the studies of protoplanetary disk evolution via early-formed Solar System solids, volatile abundances and distribution within the inner solar system, and geochemical and temporal investigations related to planet formation and differentiation. We also highlight opportunities through the relationship with the Center of the Advancement of Space Safety and Mission Assurance Research (CASSMAR) at the University of Texas at El Paso. CICG is open to collaborations and participates in the NASA Facility for Astromaterials Research (NFAR) program, which accepts research proposals for access to the unique facility capabilities.

Jacob B. Setera↗
NASA NTRS1994

Volatiles in the Earth: All shallow and all recycled

A case can be made that accretion of the Earth was a high-temperature process and that the primordial Earth was dry. A radial zone-refining process during accretion may have excluded low-melting point and volatile material, including large-ion lithophile elements toward the surface, leaving a refractory and zoned interior. Water, sediments and altered hydrous oceanic crust are introduced back into the interior by subduction, a process that may be more efficient today than in the past. Seismic tomography strongly suggests that a large part of the uppermantle is above the solidus, and this implies wet melting. The mantle beneath Archean cratons has very fast seismic velocities and appears to be strong to 150 km or greater. This is consistent with very dry mantle. It is argued that recycling of substantial quantities of water occurs in the shallow mantle but only minor amounts recycle to depths greater than 200 km. Recycling also oxidizes that mantle; ocean island ('hotspot') basalts are intermediate in oxidation state to island-arc and midocean ridge basalts (MORB). This suggests a deep uncontaminated reservoir for MORB. Plate tectonics on a dry Earth is discussed in order to focus attention on inconsistencies in current geochemical models of terrestrial evolution and recycling.

Anderson, Don L.↗
NASA NTRS2012

NASA Tech Briefs, March 2012

The topics include: 1) Spectral Profiler Probe for In Situ Snow Grain Size and Composition Stratigraphy; 2) Portable Fourier Transform Spectroscopy for Analysis of Surface Contamination and Quality Control; 3) In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer; 4) Physics Mining of Multi-Source Data Sets; 5) Photogrammetry Tool for Forensic Analysis; 6) Connect Global Positioning System RF Module; 7) Simple Cell Balance Circuit; 8) Miniature EVA Software Defined Radio; 9) Remotely Accessible Testbed for Software Defined Radio Development; 10) System-of-Systems Technology-Portfolio-Analysis Tool; 11) VESGEN Software for Mapping and Quantification of Vascular Regulators; 12) Constructing a Database From Multiple 2D Images for Camera Pose Estimation and Robot Localization; 13) Adaption of G-TAG Software for Validating Touch and Go Asteroid Sample Return Design Methodology; 14) 3D Visualization for Phoenix Mars Lander Science Operations; 15) RxGen General Optical Model Prescription Generator; 16) Carbon Nanotube Bonding Strength Enhancement Using Metal Wicking Process; 17) Multi-Layer Far-Infrared Component Technology; 18) Germanium Lift-Off Masks for Thin Metal Film Patterning; 19) Sealing Materials for Use in Vacuum at High Temperatures; 20) Radiation Shielding System Using a Composite of Carbon Nanotubes Loaded With Electropolymers; 21) Nano Sponges for Drug Delivery and Medicinal Applications; 22) Molecular Technique to Understand Deep Microbial Diversity; 23) Methods and Compositions Based on Culturing Microorganisms in Low Sedimental Fluid Shear Conditions; 24) Secure Peer-to-Peer Networks for Scientific Information Sharing; 25) Multiplexer/Demultiplexer Loading Tool (MDMLT); 26) High-Rate Data-Capture for an Airborne Lidar System; 27) Wavefront Sensing Analysis of Grazing Incidence Optical Systems; 28) Foam-on-Tile Damage Model; 29) Instrument Package Manipulation Through the Generation and Use of an Attenuated-Fluent Gas Fold; 30) Multicolor Detectors for Ultrasensitive Long-Wave Imaging Cameras; 31) Lunar Reconnaissance Orbiter (LRO) Command and Data Handling Flight Electronics Subsystem; and 32) Electro-Optic Segment-Segment Sensors for Radio and Optical Telescopes.

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DOE OSTI2020

Conventional and Next Generation Treatment Technologies for PFAS - 20067

In 2016, the United States Environmental Protection Agency (USEPA) established a Health Advisory Limit (HAL) for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) (individually and the summation) of 70 nanograms per liter (ng/L) based on developing toxicological information. These two compounds are among several thousand per- and polyfluoroalkyl substances (PFAS). Due to a multitude of commercially beneficial physical and chemical properties, the availability of PFAS-relevant and practical water treatment technologies is limited. The use of conventional adsorbents, such as activated carbon (AC) and anion exchange (AIX) resins, have become a 'de facto' interim measure to immediately address drinking water above this criterion. However, these adsorbents can have marginal long-term efficiency and are relatively unproven against the diversity of polyfluorinated compounds. Additionally, geochemical and/or co-contaminant competition can significantly impede adsorption based PFAS removal. These challenges may be addressed using engineered filtration, such as reverse osmosis or nanofiltration (RO/NF); however, for larger flow systems RO/NF may have unacceptable reject ratios as high as 35% and the capital cost may preclude these technologies. Extending these technologies to natural waters, which have various degrees of geochemical and co-contaminant competition, often requires a treatment train, combining conventional adsorbents or engineered filtration with pretreatment and more innovative and emerging remediation solutions for PFAS. Conventional and Next Generation water treatment technologies for PFAS generally employ one of three mechanisms (adsorption, separation, or destruction). These mechanisms include many types of technologies for both municipal drinking water and extracted natural water applications. The previously mentioned AC, AIX, and RO/NF are commercially available technologies that are actively being deployed for PFAS treatment. Research and development around these technologies is focused on optimization, and ultimate destruction of PFAS is achieved through incineration. Next Generation water treatment technologies include PFAS-specific flocculants, foam fractionation, novel AIX resins, new engineered adsorptive media, electrochemical treatment, sonolysis, and photolysis, radiation, and plasma (forms of advanced reductive processes [ARP]). Research and development around these technologies is focused on proof of concept and assimilation to real world applications. As the PFAS-relevant destructive technologies (such as incineration, electrochemical treatment, sonolysis, and ARP) are energy intensive, the state of the practice for PFAS water treatment is to focus adsorption/separation based technologies on reducing and concentrating the volume of water requiring destructive treatment. This enables more flexibility with respect to circulation frequency, residence time, and more control over energy usage. Water treatment for PFAS presently requires multiple technologies (i.e. a treatment train) to protect human health in a cost-conscious manner. An investment in research and development to explore new technologies is part of a key initiative for efficient protection of human health. This presentation attempts to review PFAS-relevant water treatment technologies and provide perspective as to their status with respect to applicability and commercial relevance. (authors)

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
NASA NTRS2004

Reflectance and Thermal Infrared Spectroscopy of Mars: Relationship Between ISM and TES for Compositional Determinations

Reflectance spectroscopy has demonstrated that high albedo surfaces on Mars contain heavily altered materials with some component of hematite, poorly crystalline ferric oxides, and an undefined silicate matrix. The spectral properties of many low albedo regions indicate crystalline basalts containing both low and high calcium pyroxene, a mineralogy consistent with the basaltic SNC meteorites. The Thermal Emission Spectrometer (TES) experiment on the Mars Geochemical Surveyor has acquired critical new data relevant to surface composition and mineralogy, but in a wavelength region that is complementary to reflectance spectroscopy. The essence of the completed research was to analyze TES data in the context of reflectance data obtained by the French ISM imaging spectrometer experiment in 1989. This approach increased our understanding of the complementary nature of these wavelength regions for mineralogic determinations using actual observations of the martian surface. The research effort focused on three regions of scientific importance: Syrtis Major-Isidis Basin, Oxia Palus-Arabia, and Valles Marineris. In each region distinct spatial variations related to reflectance, and in derived mineralogic information and interpreted compositional units were analyzed. In addition, specific science questions related to the composition of volcanics and crustal evolution, soil compositions and pedogenic processes, and the relationship between pristine lithologies and weathering provided an overall science-driven framework for the work. The detailed work plan involved colocation of TES and ISM data, extraction of reflectance and emissivity spectra from areas of known reflectance variability, and quantitative analysis using factor analysis and statistical techniques to determine the degree of correspondence between these different wavelength regions. Identified coherent variations in TES spectroscopy were assessed against known atmospheric effects to validate that the variations are due to surface properties. With this new understanding of reflectance and emission spectroscopy, mineralogic interpretations were derived and applied to the science objectives of the three regions.

Boyce, Joseph↗
DOE OSTI2022

Biogeochemical fingerprinting of magnetotactic bacterial magnetite

Biominerals are important archives of the presence of life and environmental processes in the geological record. However, ascribing a clear biogenic nature to minerals with nanometer-sized dimensions has proven challenging. Identifying hallmark features of biologically controlled mineralization is particularly important for the case of magnetite crystals, resembling those produced by magnetotactic bacteria (MTB), which have been used as evidence of early prokaryotic life on Earth and in meteorites. In this work, we show that magnetite produced by MTB displays a clear coupled C–N signal that is absent in abiogenic and/or biomimetic (protein-mediated) nanometer-sized magnetite. We attribute the presence of this signal to intracrystalline organic components associated with proteins involved in magnetosome formation by MTB. These results demonstrate that we can assign a biogenic origin to nanometer-sized magnetite crystals, and potentially other biominerals of similar dimensions, using unique geochemical signatures directly measured at the nanoscale. This finding is significant for searching for the earliest presence of life in the Earth’s geological record and prokaryotic life on other planets.

58 GEOSCIENCES↗
NASA NTRS1997

Impact Crises, Mass Extinctions, and Galactic Dynamics: A Unified Theory

A general hypothesis linking mass extinctions of life with impacts of large asteroids and comets is based on astronomical data, impact dynamics, and geological information. The waiting times of large-body impacts on the Earth, derived from the flux of Earth-crossing asteroids and comets, and the estimated size of impacts capable of causing large-scale environmental disasters predict that impacts of objects (sup 3)5 km in diameter ((sup 3)10(exp 7) Mt TNT equivalent) could be sufficient to explain the record of about 25 extinction pulses in the last 540 m.y., with the five recorded major mass extinctions related to the impacts of the largest objects of (sup 3)10 km in diameter ( (sup 3)10(exp 8) Mt events). Smaller impacts (about 10(exp 6)-10(exp 7) Mt), with significant regional and even global environmental effects, could be responsible for the lesser boundaries in the geologic record. Tests of the "kill curve" relationship for impact-induced extinctions based on new data on extinction intensities and several well-dated large impact craters suggest that major mass extinctions require large impacts, and that a step in the kill curve may exist at impacts that produce craters of -100 km diameter, with smaller impacts capable of only relatively weak extinction pulses. Single impact craters < about 60 km in diameter should not be associated with global extinction pulses detectable in the Sepkoski database (although they may explain stage and zone boundaries marked by lesser faunal turnover), but multiple impacts in that size range may produce significant stepped extinction pulses. Statistical tests of the last occurrences of species at mass-extinction boundaries are generally consistent with predictions for abrupt or stepped extinctions, and several boundaries are known to show "catastrophic" signatures of environmental disasters and biomass crash, impoverished postextinction fauna and flora dominated by stress-tolerant and opportunistic species, and gradual ecological recovery and radiation of new taxa. Isotopic and other geochemical signatures are also generally consistent with the expected after-effects of catastrophic impacts. Seven of the recognized extinction pulses are associated with concurrent (in some cases multiple) stratigraphic impact markers (e.g., layers with high Ir, shocked minerals, microtektites), and/or large, dated impact craters. Other less-well-studied crisis intervals show elevated Ir, still well below that of the K/T spike, which might be explained by low-Ir impactors, ejecta blowoff, or the sedimentary reworking and dilution of impact signatures. The best explanation for a possible periodic component of about 30 m.y. in mass extinctions and clusters of impacts is the modulation of the comet flux associated with the solar system's periodic passage through the plane of the Milky Way Galaxy. The quantitative agreement among paleontological, geological, and astronomical data suggests an important underlying unification of the processes involved.

Rampino, M.R.↗