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2012 Annual Science Report

Carnegie Institution of Washington Reporting  |  SEP 2011 – AUG 2012

Executive Summary

The NASA Astrobiology Institute team led by the Carnegie Institution of Washington is dedicated to the study of the extrasolar planets, solar system formation, organic rich primitive planetary bodies, deep sequestration of CHON volatiles in terrestrial planets, prebiotic molecular synthesis through geocatalysis, and the connection between planetary evolution the emergence, and sustenance of biology – processes central to the missions of the NAI. Our program attempts to integrate the sweeping narrative of life’s history through a combination of bottom-up and top-down studies. On the one hand, we study processes related to chemical and physical evolution in plausible prebiotic environments – circumstellar disks, extrasolar planetary systems and the primitive Earth. Complementary to these bottom-up investigations of life’s origin, we will continue our field and experimental top-down efforts to document the nature of microbial life at extreme conditions, as well as the characterization of organic matter in ancient fossils. Both types of efforts inform our development of biotechnological approaches to life detection on other worlds.

Our team’s research focus on life’s chemical and physical evolution, from the interstellar medium, through planetary systems, to the emergence and detection of life, across five integrated and interdisciplinary areas of research:

1. We continue to apply theory and observations to investigate the nature and distribution of extrasolar planets both through radial velocity and astrometric methods, the composition of circumstellar disks, early mixing and transport in young disks, and late mixing and planetary migration in the Solar System, and Solar System bodies.

2. We conduct observational analytical research on the volatile and organic rich Solar System Bodies by focusing on astronomical surveying of outer solar system objects and performing in-house analyses of meteorite, interplanetary dust particle, and Comet Wild 2/81P samples with an emphasis on characterizing the distribution, state and chemical history of primitive organic matter.

3. We study the origin and evolution of the terrestrial planets with a special emphasis on CHON volatiles, their delivery and retention in the deep interiors of terrestrial planets. We will experimentally investigate how CHON volatiles may be retained even during magma ocean phases of terrestrial evolution. We investigate the early Earth’s recycling processes studying the isotopic composition of diamonds, diamond inclusions, and associated lithologies. We address how early geotectonic processes lead to the diversification of minerals perhaps required for the origin of life and certainly later modified by the presence of life.

4. We investigate the geochemical steps that may have lead to the origin of life, focusing on identifying and characterizing mineral catalyzed organic reaction networks that lead from simple volatiles, e.g., CO2, NH3, and H2, up to greater molecular complexity. We explore the role of minerals to enhance molecular selection, both isomeric and chiral selection, as well as molecular organization on mineral surfaces.

5. We study the intersection between geology and biology. We continue to explore how sub-seafloor interactions support deep ocean hydrothermal ecosystems. We study life’s adaption to extremes of pressure, cold, and salinity. We adapt and apply multiple isotopic sulfur geochemistry towards the understanding of microbial metabolism and as a means of detecting ancient metabolisms recorded in the rock record through characteristic sulfur isotopic signatures. We apply state-of-the-art methods to derive chemical and isotopic biosignatures of life in the Earth’s most ancient rocks.

Fuller understanding of life’s origin, evolution, and distribution requires major advances on all these topics, as well as the extensive challenge of integrating these topics. During the next three years of NAI support we anticipate significant progress in each of these six areas, as well as considerable advances derived from integrating these theoretical, experimental, and field studies.

Highlights in the area of Studies of the Physical and chemical evolution of planetary systems during the past year (2011-2012) include the following:

*Co-I Butler continued his work on radial velocity searches for exoplanets in the Lick-Carnegie survey, Anglo-Australian Planet Search, and Magellan Planet Finding survey. He expects to soon bring on line the dedicated 2.4 m Automated Planet Finder telescope. The goal is to find the smallest mass planets, and potentially habitable mass planets, around the nearest stars.

*NAI-supported postdoctoral researcher Guillem Anglada-Escudé developed a new algorithm for obtaining precision radial velocities from the HARPS instrument operated by the European Southern Observatory. This method, named “Template-Enhanced Radial velocity Re-analysis Application” or TERRA provides significant improvement in low amplitude signal detection, especially around M-type stars.

*Co-I Boss leads the Carnegie Astrometric Planet Search (CAPS) project at LCO, while Co-I Weinberger and NAI supported postdoctoral researcher Anglada-Escudé are key members of the CAPS team. The CAPS team is undertaking an astrometric search for gas giant planets and brown dwarfs orbiting nearby low mass dwarf stars with the LCO du Pont telescope. We are following 100 nearby (primarily within about 15 pc) low mass stars, principally late M, L, and T dwarfs, for 10 years or more. Our latest paper (Anglada-Escudé et al. 2012) places an astrometric upper mass limit on the known Doppler exoplanet GJ 317b.

*Co-I Boss is also working on mixing and transport in marginally gravitationally unstable disks. Along with Co-I Conel Alexander, Boss and and collaborator Podolak published a paper in EPSL in 2012 that describes 3D hydrodynamical models of the trajectories of particles in the solar nebula that show that cm-sized particles can traverse distances of 10 AU or more, both inward and outward, in the midplane of the nebula, in less than 1000 yrs.

*NAI-supported postdoctoral researcher Nick Moskovitz and collaborators have focused on obtaining multi-wavelength observations of near-Earth asteroids during very close approaches to the Earth. Such observations are challenging due to the rapid motion of the asteroids and the specific timing requirements, the proximity of the targets, and thus their apparent brightness during these events.

*The star TW Hydrae sports a massive disk. Because it is the nearest example of a protoplanetary disk, Co-I Weinberger has used HST data to study its structure and composition. Weinberger and collaborators have determined parallaxes to fourteen primary stars identified as TWA members, to greatly expanded the knowledge of the kinematics of these young stars.

Highlights in the area of Studies of the Origin and Evolution of Organic matter in the Solar System during the past year (2011-2012) include the following:

*Co-I Scott Sheppard and collaborators have measured the optical colors of 58 outer Solar System objects in mean motion resonance with Neptune. They find that the various Neptune resonant populations have significantly different surface color distributions. This indicates vastly different origins and evolutions for the objects in resonance with Neptune, with implications for the origins of volatiles in the inner and outer solar system.

*Co-Is Nittler, Alexander, Stroud, and Cody have continued their coordinated multi-technique microanalytical studies of meteoritic organic matter, both in situ and as isolated insoluble organic matter (IOM) residues. This year, we have extended this research to several more micron-sized C inclusions in this meteorite and CR2 GRA 95229. They find that an original 15N- and nitrile-enriched material may have been preferentially protected against parent-body processing in larger carbonaceous inclusions.

*Coordinated micro-analysis of carbonaceous nano-globules reveals a range of textures and chemically distinct classes of material, suggesting a complex history of organic synthesis early in Solar System history.

*This year the CIW-NAI team began a new collaboration with Sachiko Amari at Washington University to investigate the structure of carbonaceous residues from the Saratov (L4) ordinary chondrite. Electron microscopy studies of the Saratov residues carried out by Stroud demonstrate that only phase of carbon present in these residues in porous nanoscale graphene, similar to activated carbon.

*Co-Is Alexander, Fogel and Nittler show that the D/H ratios of water in carbonaceous chondrites are lower than those in comets and Enceladus, implying that the chondrites formed in a different region of the Solar System, probably much closer to the Sun, contrary to the predictions of recent dynamical models. The D/H ratios of water in carbonaceous chondrites also argue against an influx of water ice from the outer Solar System that has been invoked to explain the non-solar oxygen isotopic composition of the inner Solar System. Finally, we argued that the bulk H and N isotopic compositions of CI chondrites suggest that they were the principal source of the Earth’s volatiles.

*Co-Is Cody, Alexander and Fogel along with Post Doctoral Fellows Wang and Kebukawa have measured large intramolecular D/H fractionation in chondritic organic solids using Solid State Nuclear Magnetic Resonance (NMR) spectroscopy. These measurements may place significant constraint on the origin and evolution of the D/H of solar system water.

Highlights in the area of Studies of the Origin, evolution, and volatile inventories of terrestrial planets during the past year (2011-2012) include the following:

*CoI Chambers has examined the role of giant impacts in the final stage of planetary accretion. This stage begins with tens or hundreds of lunar-to-Mars-sized planetary embryos and ends with a handful of rocky planets that move on stable orbits. These new simulations show that nearly half of collisions are of the hit and run kind, with no net growth. However, the timescale required for an Earth-like planet to acquire most of its mass is essentially unchanged. Collision rates are higher as a result.

*Co-I Solomon is the Principal Investigator and Co-I Nittler the Deputy Principal Investigator of the MESSENGER mission to Mercury. As part of this NAI project, Solomon and Nittler are integrating the information derived from MESSENGER into a better understanding of the processes that led to the formation of the small, embryo-sized inner planets, including Mercury at about 5% of Earth’s mass and Mars at about 10%. That the bulk compositions, volatile abundances, magmatic histories, and magnetic field histories differ so strongly on these two bodies demonstrates the strongly stochastic nature of the planet-building process and probably some dependence on solar distance.

*CoI’s Mysen and Fogel working with collaborator Foustoukos have studied in-situ the behavior of silicate-saturated fluids coexisting with fluid-saturated silicate melts. Physicochemical behavior was determined in-situ with the materials at temperature (up to 900˚C) and pressure (up to 2250 MPa) with samples contained in an Ir-gasketed hydrothermal diamond anvil cell (HDAC).

*PI Cody with NAI Post Doc Wang and CoI Mysen have been applying D and H solid state NMR to study intramolecular isotope fractionation in silicate glasses quenched from melts. We find very large differences in the affinity of D or H in different molecular environments within the quenched melts. Such fractionation arises not due to any thermal equilibrium effects or kinetic isotope effects, but rather due to partial molar volume differences between OH and OD species.

*CoIs Steele Mysen, and Fogel and a number of collaborators have had two important papers published on reduced organic carbon compounds on Mars. In the first study they used confocal Raman imaging spectroscopy and transmission electron microscopy to study organic carbon in the Martian meteorite Allan Hills (ALH) 84001. Given that the Mars Science Laboratory mission is targeted at Gale crater, the questions raised as to the formation of reduced carbon species from ground water interactions or from impact processes should be measurable by the Sample Analysis at Mars (SAM) instrument.

*Co-I Shirey, is studying ancient surface geological processes seen on Earth’s continents through the 150 km depths of their continental lithospheric mantle keels into the convecting mantle below and back in time. Such recycling is a fundamental geodynamic process that has occurred on Earth in some form since it accreted. Shirey has been investigating the implications of a geodynamic shift for the composition, structure and heat budget of the earliest Earth and how continental crust is constructed during the transition to more traditional plate tectonics.

*CoI Hazen is studying the mineralogy of the Hadean Eon, encompassing Earth’s first 700 million years, a time of significant planetary evolution. CoI Hazen and collaborators estimate that prebiotic Earth’s near-surface environment held no more than about 410 different rock-forming or accessory mineral species that were widely distributed and/or volumetrically significant. This Hadean mineralogical parsimony, perhaps comparable to the mineral diversity of the near-surface environment of Mars today, is a consequence of the relatively limited modes of mineral paragenesis prior to 3.85 Ga compared to the last 3.0 billion years.

Highlights in the area of Studies of the Geochemical steps leading to the origins of life during the past year (2011-2012) include the following:

*Former NAI PD fellow Shohei Ohara working with PI Cody continued their studies of organic-mineral interactions. They find that in reactions involving citric acid and FeS considerable dissolution of FeS occurs at near ambient temperatures; the iron-citrate clusters spontaneously react to form pyruvate through an iron catalyzed retro-aldol reaction.

*NAI PD fellow Codi Lazar working PI Cody and collaborator Craig Manning (UCLA) completed their work on pressure catalyzed methanogenesis. In this set of experiments it is found that in the absence of catalysts, increased pressure strongly increases the rate of methane formation from CO2 and H2.

*NAI PD Klotchko and CoI’s Hazen and Sverjenky have studied interactions of pentose sugars on rutile (a-TiO2, pHPPZC = 5.4, BET = 18.1 m2/g) in pure water, 10 and 100 mM NaCl and synthetic seawater solutions with 5 < pH < 10. Batch adsorption experiments of the four sugars individually and in mixtures indicate that adsorption increases with increasing pH and salt concentration of the solution. The salt effect and pH dependancy of adsorption is more pronounced for ribose. Ribose adsorption is the strongest among the sugars, suggesting that ribose’s cis diol OH-groups play a critical role in the attachment to mineral surfaces.

*NAI supported pre Doc Lee and NAI colleagues have conducted in situ SERS measurements to probe the attachment configurations of the organic molecule DOPA on nano-rutile at different pH values. The SERS spectra show signals that progressively change between pH values of 3 to 6 (Figure 4), indicating a change from the “lying down” to “standing up”, thereby validating the model predictions of two different surface complexes.

*Predoctoral student Lee and NAI colleagues performed hydrothermal experiments to investigate the influence of redox conditions on the stability of glutamic acid at pressures and temperatures reflecting near-seafloor hydrothermal environments (100–250 oC, 136 bar). It is found that the decomposition of glutamic acid is strongly inhibited by the redox state imposed by a dissolved H2.

Highlights in the area of Studies of Geobiological-Biological Interactions during the past year (2011-2012) include the following:

*CoI Schrenk and colleagues expanded their study of the sub-surface environments associated with hydrothermal vents, to include viruses so as to assess their possible role in effecting the genetic landscape of the microbial communities. They find that viruses are likely to play a crucial role in facilitating adaptability to the extreme conditions of these regions of the deep biosphere.

*CoI Baross and students have completed analyses of the microbial community structure in hydrothermal fluid gradients associated with diffuse-flow vents and vent plumes. Surprisingly, a high incidence of a single species of sulfur metabolizing bacteria was found in the plume samples. These sulfur-oxidizing species are cosmopolitan and are frequently seen in oxygen minimum zones.

*Collaborators Glamoclija, Rogers, and Bowden, working with CoIs Fogel, and Steele have started a new exciting project studying carbon cycling related to volcanic processes at the Campi Felgrei Deep Drilling Site, Southern Italy.

*NAI post Doc Pérez-Rodríguez working with collaborator and mentor Foustoukos participated in a multi-institutional/international/interdisciplinary project in collaboration with Stefan Sievert (WHOI), Costantino Vetriani (Rutgers), and Nadine Le Bris (CNRS) to study shallow water vent systems in Palaeochori Bay off Milos (Greece). Currently, they are characterizing the chemical and isotopic signatures of specific microbial community composition at these sites and performing culture-dependent studies to constrain chemolithoautotrophic dissimilatory Fe(III) reduction metabolism from microorganisms belonging to these communities.

*CoI Farquhar and students have continued to use the multiple isotopic systematics of sulfur to better undertand microbial sulfur metabolism. This very large project involves six members of the Farquhar group.

*NAI post Doc Pérez-Rodríguez with collaborators Foustoukos and Sievert (Woods Hole) and CoI Fogel are studying experimentally nitrogen metabolisms of deep-sea vent chemosynthetic microbes at in situ seafloor pressures. These data will help to improve the understanding of nitrogen metabolism in anaerobic chemosynthetic nitrate reducing microorganisms at deep-sea hydrothermal vents.

*Former NAI Post Doc Wang and CoI’s Cody, Fogel and Steele have developed a novel approach towards following hydrogen isotope fractionation in bacteria during exponential growth using a combination of D and H solid state NMR and structural mass spectrometry. They find that that membrane lipids are enriched in deuterium over protein aminoacids by 600 permil.