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NASA NTRS2004

Evidence for Terrestrial Organic Contamination of the Tagish Lake Meteorite

The Tagish Lake meteorite is a rare discovery in the meteorite world. Tentatively classified as an ungrouped type 2 carbonaceous chondrite, it is the first known CI2 meteorite [1, 2, 3]. Tagish Lake is the first meteorite to exhibit a reflectance spectrum showing the red color characteristic of the D- and P-type asteroids that populate the outer main-belt [2], although many interplanetary dust particles collected from the Earth s stratosphere exhibit a similar spectrum [4]. Several large pieces of the Tagish Lake meteorite were recovered on Jan. 18, 2000. We obtained two samples of the Tagish Lake meteorite, both collected on April 24, 2000, designated MG02 and MG03, from A. Hildebrand (Univ. of Calgary) and P. Brown (Univ. of Western Ontario). Smaller fragments collected in May 2000 were purchased from the The Meteorite Market (samples designated "MM"). We have reported preliminary results from infrared and X-ray Absorption Near-edge Structure (XANES) spectroscopy on the MM samples [5]. We report evidence to suggest that there was terrestrial contamination of the meteorite, even in fragments in contact with the lake ice for only a few months .

Wirick, S.↗
NASA NTRS2006

Thermal Constraints from Siderophile Trace Elements in Acapulcoite-Lodranite Metals

A fundamental process in the formation of differentiated bodies is the segregation of metal-sulfide and silicate phases, leading to the formation of a metallic core. The only known direct record of this process is preserved in some primitive achondrites, such as the acapulcoite-lodranites. Meteorites of this clan are the products of thermal metamorphism of a chondritic parent. Most acapulcoites have experienced significant partial melting of the metal-sulfide system but not of silicates, while lodranites have experienced partial melting and melt extraction of both. The clan has experienced a continuum of temperatures relevant to the onset of metal mobility in asteroidal bodies and thus could yield insight into the earliest stages of core formation. Acapulcoite GRA 98028 contains relict chondrules, high modal sulfide/metal, has the lowest 2-pyroxene closure temperature, and represents the least metamorphosed state of the parent body among the samples examined. Comparison of the metal-sulfide component of other clan members to GRA 98028 can give an idea of the effects of metamorphism.

Herrin, Jason S.↗
NASA NTRS2009

Elemental Composition of 433 Eros: New Calibration of the NEAR-Shoemaker XRS Data

We present a new calibration of the elemental-abundance data for Asteroid 433 Fros taken by the X-ray spectrometer (XRS) aboard the NEAR-Shoemaker spacecraft. (NEAR is an acronym for "Near-Earth Asteroid Rendezvous,") Quintification of the asteroid surface elemental abundance ratios depends critically on accurate knowledge of the incident solar X-ray spectrum, which was monitored simultaneously with asteroid observations. Previously published results suffered from incompletely characterized systematic uncertainties due to an imperfect ground calibrations of the NEAR gas solar monitor. The solar monitor response function and associated uncertainties have now been characterized by cross-calibration of a large sample of NEAR solar monitor flight data against. contemporary broadband solar X-ray data from the Earth-orbiting GOES-8 (Geostationary Operational Environmental Satellite). The results have been used to analyze XRS spectra acquired from Eros during eight major solar flares (including three that have not previously been reported). The end product of this analysis is a revised set of Eros surface elemental abundance ratios with new error estimates that more accurately reflect the remaining uncertainties in the solar flare spectra: Mg/Si=.753 +0.078/-0.055, Al/Si=0.069 +/-0.055, S/Si=0.005+/-0.008, Ca/Si=0.060+0.023/-0.024, and Fe/Si= 1.578+0.338/-0.320. These revised abundance ratios are consitent within cited uncertainties with the results of Nittler et al. [Nittler, L.R., and 14 colleagues, 2001. Meteorit Planet. Sci 36, 1673-1695] and thus support the prior conclusions that 433 Eros has major-element composition simular to ordinary chondrites with the exception of a stong depletoin in sulfur, most likely caused by space weathering.

Lim, Lucy F.↗
NASA NTRS2008

Proceedings of the 39th Lunar and Planetary Science Conference

Sessions with oral presentations include: A SPECIAL SESSION: MESSENGER at Mercury, Mars: Pingos, Polygons, and Other Puzzles, Solar Wind and Genesis: Measurements and Interpretation, Asteroids, Comets, and Small Bodies, Mars: Ice On the Ground and In the Ground, SPECIAL SESSION: Results from Kaguya (SELENE) Mission to the Moon, Outer Planet Satellites: Not Titan, Not Enceladus, SPECIAL SESSION: Lunar Science: Past, Present, and Future, Mars: North Pole, South Pole - Structure and Evolution, Refractory Inclusions, Impact Events: Modeling, Experiments, and Observations, Mars Sedimentary Processes from Victoria Crater to the Columbia Hills, Formation and Alteration of Carbonaceous Chondrites, New Achondrite GRA 06128/GRA 06129 - Origins Unknown, The Science Behind Lunar Missions, Mars Volcanics and Tectonics, From Dust to Planets (Planetary Formation and Planetesimals):When, Where, and Kaboom! Astrobiology: Biosignatures, Impacts, Habitability, Excavating a Comet, Mars Interior Dynamics to Exterior Impacts, Achondrites, Lunar Remote Sensing, Mars Aeolian Processes and Gully Formation Mechanisms, Solar Nebula Shake and Bake: Mixing and Isotopes, Lunar Geophysics, Meteorites from Mars: Shergottite and Nakhlite Invasion, Mars Fluvial Geomorphology, Chondrules and Chondrule Formation, Lunar Samples: Chronology, Geochemistry, and Petrology, Enceladus, Venus: Resurfacing and Topography (with Pancakes!), Overview of the Lunar Reconnaissance Orbiter Mission, Mars Sulfates, Phyllosilicates, and Their Aqueous Sources, Ordinary and Enstatite Chondrites, Impact Calibration and Effects, Comparative Planetology, Analogs: Environments and Materials, Mars: The Orbital View of Sediments and Aqueous Mineralogy, Planetary Differentiation, Titan, Presolar Grains: Still More Isotopes Out of This World, Poster sessions include: Education and Public Outreach Programs, Early Solar System and Planet Formation, Solar Wind and Genesis, Asteroids, Comets, and Small Bodies, Carbonaceous Chondrites, Chondrules and Chondrule Formation, Chondrites, Refractory Inclusions, Organics in Chondrites, Meteorites: Techniques, Experiments, and Physical Properties, MESSENGER and Mercury, Lunar Science Present: Kaguya (SELENE) Results, Lunar Remote Sensing: Basins and Mapping of Geology and Geochemistry, Lunar Science: Dust and Ice, Lunar Science: Missions and Planning, Mars: Layered, Icy, and Polygonal, Mars Stratigraphy and Sedimentology, Mars (Peri)Glacial, Mars Polar (and Vast), Mars, You are Here: Landing Sites and Imagery, Mars Volcanics and Magmas, Mars Atmosphere, Impact Events: Modeling, Experiments, and Observation, Ice is Nice: Mostly Outer Planet Satellites, Galilean Satellites, The Big Giant Planets, Astrobiology, In Situ Instrumentation, Rocket Scientist's Toolbox: Mission Science and Operations, Spacecraft Missions, Presolar Grains, Micrometeorites, Condensation-Evaporation: Stardust Ties, Comet Dust, Comparative Planetology, Planetary Differentiation, Lunar Meteorites, Nonchondritic Meteorites, Martian Meteorites, Apollo Samples and Lunar Interior, Lunar Geophysics, Lunar Science: Geophysics, Surface Science, and Extralunar Components, Mars, Remotely, Mars Orbital Data - Methods and Interpretation, Mars Tectonics and Dynamics, Mars Craters: Tiny to Humongous, Mars Sedimentary Mineralogy, Martian Gullies and Slope Streaks, Mars Fluvial Geomorphology, Mars Aeolian Processes, Mars Data and Mission,s Venus Mapping, Modeling, and Data Analysis, Titan, Icy Dwarf Satellites, Rocket Scientist's Toolbox: In Situ Analysis, Remote Sensing Approaches, Advances, and Applications, Analogs: Sulfates - Earth and Lab to Mars, Analogs: Remote Sensing and Spectroscopy, Analogs: Methods and Instruments, Analogs: Weird Places!. Print Only Early Solar System, Solar Wind, IDPs, Presolar/Solar Grains, Stardust, Comets, Asteroids, and Phobos, Venus, Mercury, Moon, Meteorites, Mars, Astrobiology, Impacts, Outer Planets, Satellites, and Rings, Support for Mission Operations, Analog Education and Public Outreach.

Source record↗
DOE OSTI2025

The Simons Observatory: science goals and forecasts for the enhanced Large Aperture Telescope

We describe updated scientific goals for the wide-field, millimeter-wave survey that will be produced by the Simons Observatory (SO). Significant upgrades to the 6-meter SO Large Aperture Telescope (LAT) are expected to be complete by 2028, and will include a doubled mapping speed with 30,000 new detectors and an automated data reduction pipeline. In addition, a new photovoltaic array will supply most of the observatory's power. The LAT survey will cover about 60% of the sky at a regular observing cadence, with five times the angular resolution and ten times the map depth of the Planck satellite. The science goals are to: (1) determine the physical conditions in the early universe and constrain the existence of new light particles; (2) measure the integrated distribution of mass, electron pressure, and electron momentum in the late-time universe, and, in combination with optical surveys, determine the neutrino mass and the effects of dark energy via tomographic measurements of the growth of structure at redshifts z ≲ 3; (3) measure the distribution of electron density and pressure around galaxy groups and clusters, and calibrate the effects of energy input from galaxy formation on the surrounding environment; (4) produce a sample of more than 30,000 galaxy clusters, and more than 100,000 extragalactic millimeter sources, including regularly sampled AGN light-curves, to study these sources and their emission physics; (5) measure the polarized emission from magnetically aligned dust grains in our Galaxy, to study the properties of dust and the role of magnetic fields in star formation; (6) constrain asteroid regoliths, search for Trans-Neptunian Objects, and either detect or eliminate large portions of the phase space in the search for Planet 9; and (7) provide a powerful new window into the transient universe on time scales of minutes to years, concurrent with observations from the Vera C. Rubin Observatory of overlapping sky.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Asteroid 1986 DA: Radar evidence for a metallic composition

Radar observations of the near-Earth asteroid 1986 DA were carried out at the Arecibo Observatory in April 1986, two months after its discovery. Radar results are consistent with the hypothesis that 1986 HA is a piece of NiFe metal derived from the interior of a much larger object that melted, differentiated, cooled and subsequently was disrupted in a catastrophic collision. This 2-km asteroid might be (or have been part of) the parent body of some iron meteorites. Or 1986 DA might share the parentage and/or part of the dynamical history of some meteorites without ever having contributed any of its own ejecta to our meteorite sample. Analysis of the samples returned from 1986 DA might ultimately involve economic considerations. Meteoritic metal is mostly iron with about 8 percent nickel, but also contains substantial concentrations of precious and strategic metals, including approx. 1 ppm of gold and approx. 10 ppm of platinum group elements. If these abundances apply to 1986 DA, it contains some 10(exp 16) g of iron, 10 (exp 15) g of nickel, 10(exp 11) g of platinum group metals, and 10(exp 10) g of gold.

Ostro, Steven J.↗
NASA NTRS2012

Regolith Depth, Mobility, and Variability on Vesta from Dawn's Low Altitude Mapping Orbit

Regolith, the fragmental debris layer formed from impact events of all sizes, covers the surface of all asteroids imaged by spacecraft to date. Here we use Framing Camera (FC) images [1] acquired by the Dawn spacecraft [2] from its low-altitude mapping orbit (LAMO) of 210 km (pixel scales of ~20 m) to characterize regolith depth, variability, and mobility on Vesta, and to locate areas of especially thin regolith and exposures of competent material. These results will help to evaluate how the surface of this differentiated asteroid has evolved over time, and provide key contextual information for understanding the origin and degree of mixing of the surficial materials for which compositions are estimated [3,4] and the causes of the relative spectral immaturity of the surface [5]. Vestan regolith samples, in the form of howardite meteorites, can be studied in the laboratory to provide complementary constraints on the regolith process [6].

Denevi, B. W.↗
NASA NTRS1991

Occultation studies of the solar system

Occultations of stars by planets, satellites, planetary ring systems, and asteroids offer opportunities to study the occulting bodies in ways not otherwise possible from the surface of the Earth. For example, one can detect even an extremely tenuous atmosphere and can measure the temperature and density profiles of the atmosphere in regions not ordinarily sampled by spacecraft. Occultations also permit direct measurement of the size and shape of solar system objects too small to be directly resolved by groundbased telescopes. The accuracy of such determinations is typically 1-2 percent and, moreover, is independent of the distance to the object. In this investigation, upcoming occultations through wide-ranging computer searches are identified, and accurate predictions for the more important events are provided. Selected occultations are observed with specially designed portable photometric equipment.

Millis, Robert L.↗
NASA NTRS2017

Interstellar and Solar Nebula Materials in Cometary Dust

Laboratory studies of cometary dust collected in the stratosphere and returned from comet 81P/Wild 2 by the Stardust spacecraft have revealed ancient interstellar grains and molecular cloud organic matter that record a range of astrophysical processes and the first steps of planetary formation. Presolar materials are rarer meteorites owing to high temperature processing in the solar nebula and hydrothermal alteration on their asteroidal parent bodies. The greater preservation of presolar materials in comets is attributed to their low accretion temperatures and limited planetary processing. Yet, comets also contain a large complement of high temperature materials from the inner Solar System. Owing to the limited and biased sampling of comets to date, the proportions of interstellar and Solar System materials within them remains highly uncertain. Interstellar materials are identified by coordinated isotopic, mineralogical, and chemical measurements at the scale of individual grains. Chondritic porous interplanetary dust particles (CP IDPs) that likely derive from comets are made up of 0.1 - 10 micron-sized silicates, Fe-Ni-sulfides, oxides, and other phases bound by organic material. As much as 1% of the silicates are interstellar grains that have exotic isotopic compositions imparted by nucleosynthetic processes in their parent stars. Crystalline silicates in CP IDPs dominantly have normal isotopic compositions and probably formed in the Solar System. 81P samples include isotopically normal refractory minerals that resemble Ca-Al rich inclusions and chondrules common in meteorites. The origins of sub-micron amorphous silicates in IDPs are not certain, but at least a few % of them are interstellar grains. The remainder have isotopic compositions consistent with Solar System origins and elemental compositions that are inconsistent with interstellar grain properties, thus favoring formation in the solar nebula [4]. The organic component in comets and primitive meteorites has large enrichments in D/H and N-15/N-14 relative to terrestrial materials. These isotopic signatures are probably due to low temperature chemical processes in cold molecular clouds or the outermost reaches of the protoplanetary disk. The greatest isotopic anomalies are found in sub-micron organic nanoglobules that show chemical signatures of interstellar chemistry. The observation that cometary dust is mostly composed of isotopically normal minerals within isotopically anomalous organic matter is difficult to reconcile with the formation models of each component. The mineral component likely formed in high temperature processes in the inner Solar System, while the organic fraction shows isotopic and chemical signatures of formation near 10 K. Studying more primitive remnants of the Solar System starting materials would help in resolving this paradox. Comets formed across a vast expanse of the outer disk under differing thermal and collisional regimes, and some are likely to be better preserved than others. Finding truly pristine aggregates of presolar materials may require return of a pristine sample of comet nucleus material.

Messenger, Scott↗
DOE OSTI2018

Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short-term heating on chondritic organics

We present in this study the effects of short-term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmothermometers. The kinetics of short-term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short-duration local heating. In an attempt to understand the effects of short-term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X-ray microscopy utilizing X-ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s-σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long-term internal heating.

Chan, Queenie H. S.↗
DOE OSTI2020

OrganiCam: First Camera for Noncontact Biodetection in Space

Los Alamos National Laboratory designed a compact laser-induced fluorescence imaging camera with Raman spectrometer to identify organic molecules and biosignatures in environments such as Martian caves, icy-moons, and asteroid surfaces. OrganiCam is the primary instrument on the Laser-Induced Fluorescence Exploration of Caves for Organics and Volatiles using an Elevated Platform (LIFE COVE) NASA mission concept. OrganiCam could also determine if instruments being sent into space for NASA are sterile and analyze samples returned to Earth. OrganiCam’s robust design for extreme environments, portability, simple operation, and low power requirement build on LANL’s 50+ years designing robotic instruments for space applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 22

The Lunar and Planetary Science XXXVI, Part 22 is presented. The topics include: 1) Pressure Histories from Thin and Thick Shock-induced Melt Veins in Meteorites; 2) Nano-structured Minerals as Signature of Microbial Activity; 3) The Insoluble Carbonaceous Material of CM Chondrites as Possible Source of Discrete Organics During the Asteroidal Aqueous Phase; 4) Discovery of Abundant Presolar Silicates in Subgroups of Antarctic Micrometeorites; 5) Characteristics of a Seismometer for the LUNAR-A Penetrator; 6) Heating Experiments of the HaH 262 Eucrite and Implication for the Metamorphic History of Highly Metamorphosed Eucrites; 7) Measurements of Ejecta Velocity Distribution by a High-Speed Video Camera; 8) Petrological Comparison of Mongolian Jalanash Ureilite and Twelve Antarctic Ureilites; 9) Metallographic Cooling Rate of IVA Irons Revisited; 10) Inhomogeneous Temperature Distribution in Chondrules in Shock-Wave Heating Model; 11) Subsurface Weathering of Rocks and Soils at Gusev Crater; 12) Extinct Radioactivities in the Early Solar System and the Mean Age of the Galaxy; 13) Correlation of Rock Spectra with Quantitative Morphologic Indices: Evidence for a Single Rock Type at the Mars Pathfinder Landing Site; 14) Silicon Isotopic Ratios of Presolar Grains from Supernovae; 15) Current Status and Readiness on In-Situ Exploration of Asteroid Surface by MINERVA Rover in Hayabusa Mission; 16) Long Formation Period of Single CAI: Combination of O and Mg Isotope Distribution; 17) Supra-Canonical Initial 26Al/27Al Indicate a 105 Year Residence Time for CAIs in the Solar Proto-Planetary Disk; 18) Evolution of Mercury's Obliquity; 19) First Results from the Huygens Surface Science Package; 20) Polyhedral Serpentine Grains in CM Chondrites; 21) Mountainous Units in the Martian Gusev Highland Region: Volcanic, Tectonic, or Impact Related? 22) Petrography of Lunar Meteorite MET 01210, A New Basaltic Regolith Breccia; 23) Earth-Moon Impacts at ~300 Ma and ~500 Ma Ago; 24) Chemical and Isotopic Analyses of Apollo 16 Glasses: An Integrated Approach; 25) Measuring the Surfaces on Mars; 26) Melting in Martian Snowbanks; 27) The Effect of Ni on Fe-FeS Phase Relations: Implications for the Chemistry of the Martian Core; 28) Shorelines in the Western United States as Analogs for Hypothesized Shoreline Features on Mars; 29) Al and Ti Isotopic Ratios of Presolar SiC Grains of Type Z; 30) Physicochemical Conditions of Clinopyroxene Crystallization in the Parental Bodies of Ordinary Chondrites; 31) Metamorphosed CM and CI Carbonaceous Chondrites Could be from the Breakup of the Same Earth-crossing Asteroid; 32) Aqueous Alteration and Hydrogen Generation on Parent Bodies of Unequilibrated Ordinary Chondrites: Thermodynamic Modeling for the Semarkona Composition; and 33) Preliminary Analysis of Relative Abundances of Hydrothermal Alteration Products in the C1-N10, Y6-N19, and Yax-1_863.51 Impact Melt Samples, Chicxulub Structure, Mexico

Source record↗
NASA NTRS2001

Exploration of the Eltanin Impact Area (Bellingshausen Sea): Expedition ANT XVIII5a

The impact of the Eltanin asteroid into the Bellingshausen Sea (2.15 Ma) is the only known impact in a deep-ocean (approx. 5 km) basin. On 26 March 2001, the FS Polarstern returned to the impact area during expedition ANT XVIII/5a. Over a period of 14 days, this region was explored by detailed bathymetric mapping, acoustic profiling of sediment deposits, and direct sampling with 18 piston cores and four gravity cores. Preliminary shipboard examination of microfossils showed that sixteen of the piston cores and three gravity cores contained sediments at least as old as the impact event and have a high probability of containing a record of the disturbances caused by the impact. During the expedition, portions of eleven piston cores were opened for preliminary examination of the impact deposits. Visual examination of cores and microscopic identification of suspect impact melt particles were were used to identify ejecta and X-ray radiographs of the opened core segments permitted analysis of sediment structures. Impact deposits were found in nine of the eleven opened cores, and a similar success rate is anticipated in the seven cores remaining to be opened. These preliminary observations indicate that the highest concentrations of meteoritic ejecta and the largest particle sizes appear to occur in the region north of the San Martin seamounts. Recovered debris includes cm-sized melt rocks and a 2.5 cm meteorite. This expedition has confirmed the presence of high concentrations of meteoritic ejecta across a region at least as large as 10(exp 5) sq km. Quantitative analyses of ejecta distribution within this region will require further study, but previous estimates of 1 km for the minimum diameter of the Eltanin asteroid, appear safe.

Gersonde, Rainer↗
NASA NTRS2013

Two-step Laser Time-of-Flight Mass Spectrometry to Elucidate Organic Diversity in Planetary Surface Materials.

Laser desorption/ionization time-of-flight mass spectrometry (LD-TOF-MS) holds promise to be a low-mass, compact in situ analytical capability for future landed missions to planetary surfaces. The ability to analyze a solid sample for both mineralogical and preserved organic content with laser ionization could be compelling as part of a scientific mission pay-load that must be prepared for unanticipated discoveries. Targeted missions for this instrument capability include Mars, Europa, Enceladus, and small icy bodies, such as asteroids and comets.

Europa↗
NASA NTRS2023

Characterizing Space Weathering Features in Grains From Asteroid Ryugu

Airless bodies such as asteroids are characterized by a lack of a protective atmosphere to guard against the effects of micrometeorite bombardment and solar wind irradiation. These processes, cumulatively known as space weathering, alter the microstructural and chemical properties of grains on asteroidal surfaces, signatures of which are recognized as vesiculated textures, amorphous grain rims, and fe-bearing nanoparticles. The accumulation of these features also causes changes in the optical properties of the surface regolith, complicating the interpretation of remote sensing data and the characterization of returned samples.

L. E. Melendez↗
NASA NTRS2010

The Impact History Of The Moon

The bombardment history of the Earth-Moon system has been debated since the first recognition that the circular features on the Moon may be impact craters. Because the lunar impact record is the only planetary impact record to be calibrated with absolute ages, it underpins our understanding of geologic ages on every other terrestrial planet. One of the more remarkable results to come out of lunar sample analyses is the hypothesis that a large number of impact events occurred on the Moon during a narrow window in time approximately 3.8 to 4.1 billion years ago (the lunar cataclysm ). Subsequent work on the lunar and martian meteorite suites; remote sensing of the Moon, Mars, asteroids, and icy satellites; improved dynamical modeling; and investigation of terrestrial zircons extend the cataclysm hypothesis to the Earth, other terrestrial planets, and possibly the entire solar system. Renewed US and international interest in exploring the Moon offers new potential to constrain the Earth-Moon bombardment history. This paper will review the lunar bombardment record, timing and mechanisms for cataclysmic bombardment, and questions that may be answered in a new age of exploration.

Cohen, B. A.↗
NASA NTRS2017

Organic Matter in Extraterrestrial Water-Bearing Salt Crystals

Introduction: Direct samples of early Solar System fluids are present in two thermally-metamorphosed ordinary chondrite regolith breccias (Monahans (1998) [H5] and Zag [H3-6]), which were found to contain brine-bearing halite (NaCl) crystals that have been added to the regolith of an S-type asteroid following asteroidal metamorphism [1, 2]. The brine-bearing halite grains were proposed to be formed on an icy C-type asteroids (possibly Ceres), and transferred to an S-type asteroid via cryovolcanic event(s) [3]. A unique aspect of these halites is that they contain abundant organic rich solid inclusions hosted within the halites alongside the water inclusions. Methods: We analyzed in detail the compositions of the organic solids and the amino acid content of the halite crystals with two-step laser desorption/laser ionization mass spectrometry (L(sup 2) MS), Raman spectroscopy, X-ray absorption near edge structure (XANES), nanoscale secondary ion mass spectrometry (NanoSIMS), and ultra-performance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry (UPLC-FD/QToF-MS). Results and Discussion: The L(sup 2) MS results show signatures of low-mass polyaromatic hydro-carbons (PAHs) indicated by sequences of peaks separated by 14 atomic mass units (amu) due to successive addition of methylene (CH2) groups to the PAH skeletons [4]. Raman spectra of the micron-sized solid inclusions of the halites indicate the presence of abundant and highly variable organic matter that include a mixture of short-chain aliphatic compounds and macromolecular carbon. C-XANES analysis identified C-rich areas with peaks at 285.0 eV (aromatic C=C) and 286.6 eV (vinyl-keto C=O). However, there is no 1s-sigma* exciton peak (291.7 eV) that is indicative of the development of graphene structure [5], which suggests the organics were synthesized cold. Na-noSIMS analyses show C-rich and N-rich areas that exhibit similar isotopic values with that of the IOM in the unweathered CR chondrites and less metamorphosed meteorites [6], and are moderately enriched in N-15 (delta N-15 = 106.1-164.5 per mille). The total amino acid distribution and abundance of the Zag matrix (approximately 1,940 parts per billion [ppb]) is comparable to other ordinary chondrites (60-3,330 ppb) [7, 8]. While the Zag matrix is gamma-ABA and EACA-deficient, the halite is shown to exhibit an opposite trend and is almost depleted in amino acids. The striking difference in the amino acid contents between the halite and matrix indicates their separate synthetic origins. Conclusion: Abundant, primitive, and highly-diverse N-15-rich organic compounds were detected in brine-water bearing halite crystals that were synthesized on a cryovolcanically-active asteroid. Our study suggests that the asteroidal parent body where the halite precipitated, potentially Ceres, is a host to abundance large variety organic precursors. Insoluble organic matter and amino acids can be synthesized from similar organic precusors under hydrous conditions [9].We envision that similar organic synthetic processes could have occurred on Ceres that synthesized organic solids as well as biologically relevant molecules.

Chan, Q. H. S.↗
NASA NTRS2017

Historical Trends in U.S. Antarctic Meteorite Allocations, With a Close Look at Cr Chondrites

ANSMET samples have been housed at and allocated from NASA-JSC since 1978. This nearly 40 year history of allocations from the collection has been contemporaneous with many major milestones such as the discovery that we have meteorites from Moon and Mars, missions to S-type asteroids (NEAR, Hayabusa, Dawn), and C-type asteroids (Dawn, Hayabusa 2, and OSIRIS-REx). We look for the possible influence of these major milestones on historical trends in the meteorite allocations, identify other factors that might contribute to allocation trends, and focus on the allocation history of a few select meteorites.

Righter, K.↗