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2014 Annual Science Report

Astrobiology Roadmap Objective 7.1 Reports Reporting  |  SEP 2013 – DEC 2014

Project Reports

  • Astrobiology of Icy Worlds

    Our goal in the Astrobiology of the Icy Worlds Investigation is to advance our understanding of the role of ice in the broad context of astrobiology through a combined laboratory, numerical, analytical, and field investigations. Icy Worlds team pursues this goal through four major investigations namely, the habitability, survivability, and detectability of life of icy worlds coupled with “Path to Flight” Technology demonstrations. A search for life linked to the search for water should naturally “follow the ice”. Can life emerge and thrive in a cold, lightless world beneath hundreds of kilometers of ice? And if so, do the icy shells hold clues to life in the subsurface? These questions are the primary motivation of our science investigations

    ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.1 3.2 4.1 5.1 5.2 5.3 6.2 7.1
  • Advancing Techniques for in Situ Analysis of Complex Organics: Laser Mass Spectrometry of Planetary Materials

    In this final reporting period under CAN-5, we extended the development of protocols for laser mass spectrometry (MS) for analysis of complex, nonvolatile organic molecules from the progress made last year. In particular the major area of focus was in (1) the use of tunable laser wavelengths for desorption in two-step laser MS (L2MS), and (2) the use of tandem mass spectrometry (MS/MS) for in situ molecular structure analysis. Each of these protocols has been investigated during the course of the CAN-5 project, jointly supported by NAI and instrument development (PIDDP, MatISSE) and flight (MOMA) programs. The unique aspect of these efforts is their implementation and evaluation using truly miniature, flight-like instrumentation, to optimize the benefit to real mission science.

    ROADMAP OBJECTIVES: 2.1 2.2 3.2 7.1
  • Project 3: The Origin of Homochirality

    A universal aspect of living systems on Earth is their homochirality: Life uses dextrorotary sugars and levorotary amino acids. The reasons for this are hotly debated and not close to being settled. However, the leading idea is that autocatalytic reactions grew exponentially fast at the origin of life, and whatever chiral symmetry breaking was accidentally present became amplified subsequently. We are calculating the way in which this can take place using statistical mechanics, and also trying to see how a uniform homochirality could be stable to spatial fluctuations.

    ROADMAP OBJECTIVES: 3.2 3.4 4.1 4.2 5.1 5.2 7.1 7.2
  • Investigation of Electron-Molecule Chemistry and Micrometeorite Induced Reactions on Titan’s Surface

    Low-energy electron-beam irradiation and dissociative electron attachment (DEA) experiments were performed on nitrogen-containing organic condensates as a model for cosmic-ray induced polymerization processes and charging events that can occur within Titan’s atmosphere and on Titan’s organic-rich surface. In addition, detailed analysis of meteorite surfaces were analyzed with an emphasis of understanding the corrosion of schreibersite and the role this may play in the formation of phosphorylated pre-biotic molecules.

    ROADMAP OBJECTIVES: 3.1 3.2 7.1
  • Project 1D: Iron Biogeochemistry in Chocolate Pots Hot Spring, Yellowstone National Park

    Small cores were collected from six locations along a transect following the main fluid flow path at Chocolate Pots (CP) hot spring, Yellowstone National Park. The cores were sectioned at 1 cm intervals, and the solids subjected to sequential extraction to isolate different Fe pools. The results showed that cores proximal to the vent outlet contained significant quantities of dissolved/colloidal and HCl-extractable reduced (ferrous) iron [Fe(II)]. Fe recovered from the other cores was present entirely as Fe(III). The most likely explanation for these observations is that internal generation of Fe(II) via microbial reduction is taking place in deposits proximal to the vent. This interpretation is consistent with rapid Fe(II) production during anaerobic incubation of near-vent deposits. Our results provide direct evidence of Fe(III) oxide reduction in deposits proximal to the main vent at CP, and to our knowledge represent the first demonstration of in situ Fe(III) reduction in a circumneutral-pH geothermal environment analogous to those which may have been present on the ancient Earth and Mars. Preliminary stable Fe isotope measurements on the dissolved/colloidal and 0.5M HCl-extractable Fe fractions in the CP cores suggests that Fe(III) reduction influences the isotopic composition of Fe phases proximal to the vent. A comprehensive analysis of all Fe phases in the cores is underway and will be used to develop conceptual models of controls on the stable Fe isotope composition preserved in the hot spring deposits.

    ROADMAP OBJECTIVES: 2.1 4.1 5.3 7.1
  • Biosignatures in Extraterrestrial Settings

    The Biosignatures in Extraterrestrial Environments group works on finding and characterizing exoplanets, in particular through very high resolution spectroscopy; and developing new techniques for finding exoplanets and characterizing their properties. It also works on understanding the evolution and dynamics of planetary systems, including the solar system, and the role of astrophysical processes in establishing and sustaining life in extraterrestrial environments.

    ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 4.1 4.3 6.2 7.1 7.2
  • Project 4: Vistas of Early Mars: In Preparation for Sample Return

    To understand the history of life in the solar system requires knowledge of how hydrous minerals form on planetary surfaces, and the role minerals may play in the development of potential life forms. The minerals hematite and jarosite have been identified on Mars and presented as in situ evidence for aqueous activity. This project seeks to understand (i) the conditions required for jarosite and hematite formation and preservation on planetary surfaces, and (ii) the conditions under which their “radiometric clocks” can be reset (e.g., during changes in environmental conditions such as temperature). By investigating the kinetics of noble gases in minerals, known to occur on Mars and Earth, we will be prepared to analyze and properly interpret ages measured on samples from future Mars sample return missions.

    ROADMAP OBJECTIVES: 2.1 3.1 7.1
  • Biosignatures of Ancient Rocks – Hedges Group

    Our work involves the design, assembly, and release to the public of a tree of life calibrated to geologic time (timetree). It is needed by astrobiologists to help determine the source of biomarkers for the presence of life in the geologic record.

    ROADMAP OBJECTIVES: 3.3 3.4 4.1 4.2 7.1 7.2
  • Project 1E: Microbial Communities in Chocolate Pots Hot Spring, Yellowstone National Park

    DNA was extracted from samples obtained from cores collected at six locations along a transect following the main fluid flow path at at Chocolate Pots (CP) hot spring, Yellowstone National Park. 454 pyrosequencing of 16S rRNA gene amplicons was performed on the extracts, resulting in the generation more than 70 amplicon libraries, each containing a between ca. 2500 and 7500 ca. 300 base pair-long reads. The raw reads were processed and analyzed for their phylogenetic affiliation and other comparisons using the QIIME pipeline. The results indicate that microbial communities in the upper few cm of the Fe/Si-rich CP deposits varied significantly along the sampling transect. Communities at two sites most proximal to the vent source differed substantially from one another and from communities at downstream sites. Although communities at downstream sites were not identical, they were more similar to one another than to the vent-proximal sites. A wide diversity of prokaryotic taxa, including both Bacteria and Archaea, were identified in the libraries, many of which are only distantly (e.g. <90% similarity in 16S rRNA gene sequence) related to known taxa. Communities in cores close to the vent were dominated by anaerobic taxa, many of which have the potential to function as Fe(III) reducers. This result is consistent with the relatively high abundance of reduced (ferrous) iron [Fe(II)] and the rapid rate of Fe(II) production observed in in vitro Fe(III) reduction experiments with material from sites near the vent. Abundant taxa at downstream sites included organisms related to the known Fe(II)-oxidizing organism Sideroxydans paludicola. These results are consistent with Fe geochemical data, which indicate that Fe(II) oxidation is likely the dominant Fe redox cycling pathway in deposits more than 1-2 meters from the vent source. A detailed metagenomic analysis of communities in the upper 1 cm at three sites is underway, with the goal of confirming the function of recognized taxa, and revealing the identity and function of potentially novel Fe redox cycling taxa.

    ROADMAP OBJECTIVES: 2.1 4.1 5.1 5.3 7.1
  • Project 6. Mining Archaeal Genomes for Signatures of Early Life: Comparison of Metabolic Genes in Methanogens

    Methanogenic archaea derive energy from simple starting materials, producing methane and carbon dioxide in the process. The chemical simplicity of the growth substrates and versatility of the organisms in extreme environments provide for a possibility that they could exist on other planets. By characterizing the evolution of methanogens from the most simple to most complex organism as well as their growth characteristics under controlled environments, we hope to address the question as to whether they could exist on planets such as Mars, where bursts of methane have been seen, yet no source has yet been identified.

    ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 3.3 3.4 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2
  • Biosignatures of Life in Ancient Stratified Ocean Analogs

    Instigated by Macalady and Kump in 2010, this project investigates biosignatures of life in modern analogs for stratified ancient and/or extraterrestrial oceans. The primary field site is a sinkhole in Florida. Other field site include stratified ocean analogs in the Bahamas, New York State, and the Dominican Republic. A website monitoring the activities of an informal working group on Early Earth Photosynthesis is maintained by Macalady (

    ROADMAP OBJECTIVES: 2.1 3.3 3.4 4.1 5.2 5.3 6.1 7.1 7.2
  • Titan as a Prebiotic Chemical System – Benner

    In 2007, NASA sponsored a committed of the National Academies of Science to explore whether life might exist in environments outside of the traditional habitable zone, defined as positions in a solar system where liquid surface water might be found. Alternative solvents which have analogous “habitable zones” farther away from their star include hydrocarbons, ammonia, and dinitrogen. The core question asked whether life having genetic biopolymers might exist in these solvents, which are in many cases (including methane) characterized by the need for “cold” (temperatures < 100K in the case of methane).

    These “weird” solvents would require “weird” genetic molecules, “weird” metabolic processes, and “weird” bio-structures. In pursuit of this “big picture” question, we turned to Titan, which has exotic solvents both on its surface (methane-hydrocarbon) and sub-surface (perhaps super-cooled ammonia-rich water). This work sought genetic molecules that might support Darwinian evolution in both environments, including non-ionic polyether molecules in the first and biopolymers linked by exotic oxyanions (such as phosphite, arsenate, arsenite, germanate) in the second.

    In the current year, we completed our studies that identified biopolymers that might work in hydrocarbon solvents. These studies have essentially ruled out biological processes in true cryosolvents. However, a series of hydrocarbons containing different numbers of carbon atoms (one, two, three, and four, for example, in methane, ethane, propane, and butane) cease to be cryosolvents as their chain lengths increase. These might be found on “warm Titans”. Further, they might exist deep in Titan’s hydrocarbon oceans, where heating from below would lead to warm hydrocarbon oceans.

    These studies showed that polyethers are insufficiently soluble in hydrocarbons at very low temperatures, such as the 90-100 K found on Titan’s surface where methane is a liquid at ambient pressures. However, we did show that “warm Titans” could exploit propane (and, of course, higher hydrocarbons) as a biosolvent for certain of these “weird” alternative genetic biopolymers; propane has a huge liquid range (far larger than water). Further, we integrated this work with mineralogy-based work that allows reduced molecules to appear as precursors for less “weird” genetic biomolecules, especially through interaction with various mineral species, including borates, molybdates, and sulfates.

    ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 3.2 3.4 4.1 5.3 6.2 7.1 7.2
  • Project 2A: The Catalysis Effect of Extracellular Polymeric Substances Excreted by Fermentative Bacteria on Ca-Mg Carbonate Precipitation

    Experiments show that purified non-metabolizing biomass from pure cultures of both anaerobic fermenting and sulfate-reducing bacteria closely related to those organisms present in the consortium could also catalyze the precipitation of disordered dolomite. Polysaccharides that are the dominant components in the EPS act as catalysts for weakening surface water and Mg (II) boning and enhancing dolomite crystallization. Our study contributes to the understanding of the “dolomite problem” by revealing (1) the catalytic effect of bound EPS on Ca-Mg carbonate crystallization and (2) the possible involvement of anaerobic fermenting bacteria in sedimentary dolomite formation, which has not been reported previously.

  • Biosignatures of Life in Extremely Energy-Limited Environments

    The terrestrial subsurface is the least explored habitat on earth and is characterized by darkness and reducing conditions that limit how fast microbes can obtain energy (low energy fluxes). The diversity and metabolic strategies of microbes in this environment are the subject of our investigation.

    ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.3 7.1
  • Developing New Biosignatures

    This project works to develop new biosignatures based on element, molecules, or isotopes. For example, we are working with the method secondary ion mass spectrometry (SIMS) to analyze microorganisms or microfossils. We are also looking at the Isolation and analysis of F430, archaeol, and IPL-archaeol from the Cascadia Margin. We are also interested in DNA as a biosignature. For that work, we are extracting DNA from deep sea sediment and other difficult environments. Finally, we are also investigating prebiotic molecules in order to known which carbon-containing biomolecules can not be reasonable biosignatures.

    ROADMAP OBJECTIVES: 3.1 7.1 7.2
  • Project 2C: Developing the 13C-18O Clumped Isotope Thermometer

    One of the critical parameters in understanding the evolution of the Earth is the temperature of the oceans. Proposals, for example, that early life was hyperthermophilic would be supported if there was evidence for a “hot early ocean”, which some stable isotope data support. However, arguments against a “hot early ocean” include lower solar luminosity early in Earth history, and evidence for widespread glaciations. A new geothermometer is based on the enhanced thermodynamic stability of “clumped isotopes” (e.g., 13C-18O bonds) in carbonate minerals, which exhibits a temperature dependence. However, attempts to calibrate this temperature dependence have identified kinetic isotope effects that can give apparently anomalous results. In this project, experiments were designed to systematically probe formation rate effects on 13C-18O bonding during calcite mineral lattice assembly from aqueous solutions. Preliminary results do not show a correlation between precipitation rate and 13C-18O bonding over the range investigated but do provide evidence that is being used to deconvolute and identify physiochemical conditions and processes that lead to disequilibrium in 13C-18O bonding during carbonate mineral formation.

    ROADMAP OBJECTIVES: 4.1 6.1 7.1 7.2
  • Project 2D: Magnesium Isotopes in Carbonates as a Tracer of Marine Conditions in the Early Earth

    Massive dolomitization events affect seawater Mg concentration and have a profound influence on the carbonate cycle in seawater that ultimately controls seawater chemistry and atmospheric carbon dioxide levels. The Mg isotope fractionation factor between dolomite and aqueous Mg has been experimentally constrained at 130, 160, and 220 degrees C to derive a temperature-dependent fractionation factor. This Mg isotope fractionation function has been determined to allow evaluation of the Mg isotope composition of fluids that have produced dolomite. Based on these new data it is now possible to infer secular changes in seawater Mg isotope compositions based on the analysis of sedimentary dolomites. This information can be used to infer changes in the intensity of dolomitization which removes Mg from seawater and tectonism which controls mid ocean ridge hydrothermal circulation that largely removes Mg from seawater as well as impacts weathering.

    ROADMAP OBJECTIVES: 4.1 7.1 7.2
  • Molecular Biosignatures of Redox-Sensitive Bacteria and Hyperthermophiles

    The Summons lab has been researching a range of molecular and isotopic phenomena aimed at shedding light on what controls Neoproterozoic ocean redox, evolutionary trends in the abundances of molecular fossils (biomarkers) and the enigmatic natural variability carbon isotopic compositions of organic and inorganic carbon at this time. Our studies of carotenoid pigment biomarkers for green and purple sulfur bacteria have revealed that they are ubiquitous in rock extracts of Proterozoic to Paleozoic age—implying that the shallow oceans became sulfidic more frequently than previously thought. Other projects focused on the biosynthesis of another important biomaker, the hopanoids, vesicles released from marine bacteria for interaction between cells and their environment, and the molecular signatures of microbial communities in hot springs in Yellowstone National Park.

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 7.1
  • Laboratory Investigations Into Chemical Evolution in Icy Solids From the Interstellar Medium to the Outer Solar System to Meteorites

    NAI-GCA support in 2014 helped us continue our work on amino-acid stability. In 2014, we performed radiation experiments to measure the destruction rate of glycine in CO2 ice. In particular, we found that this rate depends on concentration and temperature, and is 20-40 times greater than for glycine in H2O-ice.

    ROADMAP OBJECTIVES: 2.1 2.2 3.1 7.1 7.2
  • Project 2E: Carbonate-Associated Sulfate (CAS) as a Tracer of Ancient Microbial Ecosystems

    The chemical compound sulfate is present in ocean water and ratios of its stable isotopes of sulfur and oxygen have varied over geological time and are indicators of global geochemical processes. Other researchers have extracted trace amounts of sulfate from carbonate minerals of various ages as a glimpse into the Earth’s geological past. We are, however, applying this approach to carbonate minerals formed by microbial processes during burial of sedimentary rocks, which we hoped would give information on the microbial ecosystems. We needed to modify and develop existing methods for extracting the trace amounts of sulfate because our samples would be mineralogically much more complex. Initially, just to test the method we tried it on material from the local Monterey Formation rocks, which are of Miocene age (approx. 13 My old) and were delighted to find that the results enabled us to see the workings of a very complex microbial ecosystem with at least three different sorts of metabolism operating.

    ROADMAP OBJECTIVES: 5.2 6.1 7.1
  • Project 2F: Silicon Isotopes as a Tracer of the Coupled Fe-Si Cycle in the Archean

    Before the appearance of marine Si secreting organisms in the early Phanerozoic, the Precambrian ocean was characterized by high Si concentrations, as demonstrated by unusually abundant Precambrian age chert deposits. The Precambrian oceanic Si cycle was controlled by Si input from continental and hydrothermal sources, Si sorption and precipitation during Fe cycling, and export of Si in chemical precipitates. Reconstruction of the Precambrian Si cycle provides a better understanding of key processes that have governed the Si-rich ocean and associated environment where the earliest life on the Earth originated. Si isotopes are potential tracers for Si cycle where δ30Si values range over 4 ‰ in Precambrian rocks. However, unambiguous interpretation of Precambrian Si isotope data is limited by a lack of knowledge on Si isotope fractionation factors determined for systems applicable to the Precambrian. We have established protocols for high-precision Si isotope analysis, and conducted a series of laboratory experiments to determine Si isotope fractionation factors in simulated systems directly relevant to deposition and preservation of Archean cherts. These experiments represent the first attempt for a mechanistic understanding of Precambrian Si isotope data, and our results highlight the importance of deposition and preservation processes in affecting Si isotopic compositions preserved in Archean sedimentary records.

  • Project 2G: Iron Isotope Fractionations Among Oxide Minerals Under Acidic Conditions

    The study of Fe isotope exchange and fractionation between aqueous Fe(II) and goethite was motivated by the inferred acidic environment for early Mars, where iron oxides (i.e. jarosite, goethite) were likely present. We found that the extent of atom exchange positively correlates with increasing pH during interactions between Fe(II)aq and goethite. The decrease in extent of exchange correlates with a decrease in the amount of sorbed Fe(II) to the goethite surface, which strongly suggests that sorbed Fe(II) is the primary catalyst for inducing Fe isotope exchange. The slow rate of isotopic exchange at acidic pH suggests that stable Fe isotope compositions may be resistant to change in acidic aqueous environments, thus leading to preservation of signatures that might contribute to the understanding of ancient Mars paleoenvironments.

    ROADMAP OBJECTIVES: 2.1 5.3 7.1 7.2
  • Remote Sensing of Organic Volatiles on Mars and Modeling of Cometary Atmospheres

    During this period, Dr. Villanueva mainly worked on processing high-resolution (spectral and spatial) data of Mars acquired in January/2014 and in the observational campaigns of 2008, 2009 and 2010, using the recently developed new analytical and modeling capabilities. Unprecedented maps of the D/H ratio in water were extracted from these data, and a paper was recently accepted by Science (see below). In addition, he participated in several international conferences and collaborated on several Titan and cometary projects.

    ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 4.1 7.1
  • Taphonomy, Curiosity and Missions to Mars

    Members of our team continue to be involved in both the MER and MSL missions on Mars. On the latter mission, team members have recently documented a long-lived, habitable environment in Gale Crater dominated by rivers and lakes. Research on the mineralogy and geochemistry of rocks at the base of Mt Sharp has improved our understanding of their complex diagenetic history. Progress has also been made in linking orbital observations with those made by the rovers; this has been advanced particularly by field research at Rio Tinto and detailed laboratory experiments that constrain the relationship between mineral combinations and their signatures in infrared reflectance spectroscopy—and their effect on our ability to detect organics.

    ROADMAP OBJECTIVES: 2.1 4.1 4.2 6.1 7.1
  • The Variability of Carbon Monoxide Abundances Among Oort Cloud Comets

    Direct observations of neutral CO in multiple wavelength regimes (radio, infrared and ultraviolet) have established a wide range for measured CO abundances (relative to water), ranging from a few tenths of a percent to ~30%. But the largest complexity when interpreting measurements of CO stems from its competing roles as a primary (parent) vs product species. For instance, CO is a principal product of CO2 dissociation, so comets rich in CO2 should also reveal a significant production rate for CO — this product CO is extended and its detection is strongly dependent on the instrumental field-of-view (FOV). Prior to 2013, only six comets within 2.5 AU of the Sun (where both H2O and CO are active primary volatiles) were identified as being enriched in native CO. During late 2013, we confirmed a relatively high abundance of CO in C/2013 R1 (Lovejoy; hereafter C/2013 R1), supporting the existence of a so-far sparse (yet growing) fraction of CO-rich comets.

    ROADMAP OBJECTIVES: 1.1 3.1 3.2 7.1
  • Project 3C: The Role of Early Continental Weathering in Providing a Habitable Planet

    Recent studies of biogeochemical cycles recorded in Archean sedimentary rocks suggest an early diverse microbial ecology that may have required extensive continentally-sourced nutrients (i.e., phosphorus) early in Earth history. Widespread continental weathering is at odds, however, with studies that suggest a majority of continental crust was submerged and seawater chemistry was largely controlled by oceanic hydrothermal fluids. Here, we present new Sr and O isotope results from stratiform barite deposits from the 3.23 Ga Fig Tree Group, South Africa. The Sr and O isotope data indicate the barite was formed from a mixture of hydrothermal fluids and seawater, and that seawater was more radiogenic then previously predicted. The only appreciable source of radiogenic Sr is from continental weathering, and thus we propose that continental weathering was more extensive throughout the Archean than previously thought. This in turn has important implications for the availability of continentally-sourced nutrients to early marine environments on Earth.

    ROADMAP OBJECTIVES: 1.1 4.1 6.1 7.1 7.2
  • Project 3D: A Microbial Iron Shuttle in Early Earth Marine Basins

    Iron-based metabolisms are deeply rooted in the tree of life, and yet comparatively little attention has been paid to searching for Fe-based biosignatures as compared, for example, photosynthetically-based metabolisms. Dissimilatory Iron Reduction (DIR) is found in both Archaea and Bacteria domains of life, its electron acceptors and donors are widespread in the solar system. This project focuses on determining the basin-scale footprint of DIR in well preserved samples of Mesoarchean age (~3 Ga) in the Witwatersrand Supergroup of South Africa. Preliminary results show a trend of iron enrichment that correlates with δ56Fe depletion from the proximal shelf to the deep distal basin, which is interpreted to indicate a DIR-driven “iron pump” or “shuttle”, where microbially-produced aqueous Fe(II) on continental shelves was pumped to the deep basin and trapped as Fe-bearing sulfides or oxides. These results not only confirm that Fe-based metabolisms were important on the early Earth ~3 b.y. ago, but that it had a substantial “footprint” in the biosphere on a basin-wide scale.

    ROADMAP OBJECTIVES: 4.1 5.2 6.1 7.1 7.2
  • Project 4A: New in Situ Techniques (CLSM and Raman) Solve the Problem Presented by the Disaggregation of Acid-Macerated Organic-Walled Microfossils

    The search for evidence of past life in rocks to be returned from Mars seems likely to hinge on the use of non-intrusive, non-destructive techniques that can establish the biogenicity of any detected fossil-like objects by analyses both of their cellular morphology and molecular composition. The most promising rock types to preserve such evidence are chemically precipitated sediments such as cherts, gypsums, carbonates and phosphates — examples of all of which on Earth have been shown to be richly fossiliferous. The organic-walled microbes in such rocks are typically not amenable to investigation by the commonly used but rock-destroying technique of acid maceration. This study shows that the combined use of optical microscopy, confocal laser scanning microscopy, and Raman spectroscopy solves this problem, documenting effective means for the investigation of Mars rocks.

  • Project 4B: New SIMS Procedures for in Situ Analysis of Mass-Independent Fractionation of S Isotopes

    An in situ sulfur four-isotope analysis technique with multiple Faraday cup detectors by ion microprobe was developed and applied to detrital pyrite grains in ~2.4 Ga glaciogenic sandstone from the Meteorite Bore Member of the Turee Creek Group, Western Australia.

    ROADMAP OBJECTIVES: 4.1 7.1 7.2