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2009 Annual Science Report

Carnegie Institution of Washington Reporting  |  JUL 2008 – AUG 2009

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 six 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 continue to 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.

6. We are continuing work coordinating advanced instrument testing with our involvement with the Arctic Mars Analogue Svalbard Expedition (AMASE) in support of Mars Science Laboratory, including ChemMin, SAM as well as elements of the ExoMars payload including Raman and Life Marker Chip Instruments.

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 four 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 include the following:

  • We are continuing our radial velocity measurements and are presently discovering the first terrestrial mass planets and Solar System analogues.
  • Our CAPScam-S instrument installed on the du Pont 2.5 m telescope yields an accuracy of better than 0.4 milliarcsec, accuracy of better than 0.3 millarcsec is anticipated soon.
  • Our 3D Marginally Gravitationally Unstable (MGU) disk model reveals rapid mixing of initially highly heterogeneous distributions of volatiles to levels of ~ 10 % into the inner solar system.
  • Our wide field observations of Kuiper Belt Objects (KBOs) have detected a turnover at the faint end of the Cumulative Luminosity Function (CLU)
  • Hubble Space Telescope imaging of the HR4796 disk reveals significant flux density asymmetries revealing that sculpting of the disk has occurred by an invisible companion or an unseen planetary-mass perturber.

Highlights in the area of Origin and Evolution of Organic Matter in the Solar System during the past year include the following:

  • Our recent optical measurements of KBOs appear to prove that very red (presumably organic rich) material is a more general feature for objects farther out from the sun.
  • Advanced molecular spectroscopy of Insoluble Organic Matter (IOM) in primitive chondritic meteorites reveal that the most likely origin of IOM is from a complex mixture of sugars.
  • Correlated analyses of carbonaceous nanoglobules (nano to micron scale hollow organic spheres) appear to be ubiquitous in chondritic meteorites. These enigmatic objects appear to be generally isotopically heavy in D and 15-N, well above what is observed in bulk IOM.
  • Interplanetary Dust Particles (IDPs) likely sampled from the comet Grigg-Skjellerup are isotopically (D and 15-N) the most primitive samples yet analyzed.

Highlights in the area of The Origin, Evolution, and Volatile Inventories of Terrestrial Planets during the past year include the following:

  • Our recent calculations reveal that rapid accretion of dust to 1-1000 km diameter planetesimals is viable under plausible disk conditions. Rapid accretion appears to be the only means of making planets given our current physical models of disk evolution.
  • The Messenger mission flyby past Mercury has provided an abundance of new information regarding this enigmatic planet.
  • Methane reacted at temperatures and pressures representative of the Earth’s deep interior has been shown to react to form higher molecular weight hydrocarbons.
  • Methane solubility in silicate melts at deep crustal temperatures and pressures can reach up to 0.5 wt %, far beyond what was previously assumed.
  • Isotopic fractionation between fluid methane and soluble methane in silicate melts can vary as much as 14 permil even at temperatures in excess of 1000 K.
  • The origin and distribution of uranium minerals on the Earth’s surface has been shown to elucidate the principle of mineral evolution as a response to the rise of the Earth’s biosphere.

Highlights in the area of The Geochemical Steps Leading to the Origin of Life during the past year include the following:

  • Formaldehdye can be synthesized under hydrothermal conditions via an unexpected reaction. This reaction provides a source of formaldehyde in an environment where the direct reduction of CO2 or CO to formaldehyde is thermodynamically impossible.
  • The absorption behavior of amino-acids on mineral surfaces can be modeled accurately with a newly developed surface complexation model that integrates state-of-the-art thermodynamic parameterization.

Highlights in the area of Geological-Biological Interactions during the past year include the following:

  • Approximately 85 % of all detectible cells in a biofilm retrieved from the Lost City hydrothermal field belong to a single, novel phylotype of archaea affiliated with the order Methanosarcinales, a group that is both methane producing and methane consuming.
  • Species distribution shifts in microbial ecosystems associated with deep sea hydrothermal environments reveal that rare organisms can increase in abundance significantly on the order of years in response to environmental change.
  • Experiments into the physiological effects of pressure (e.g. ocean sea floor pressures) reveal that pressure alone can rapidly prune complex microbial communities to essentially pure cultures.
  • Even in essentially mono-mineralic, dry sulfate (gypsum) environments, e.g. the dunes in the White Sands Desert (NM), extensive biodiversity (Eubacteria, Archaea, and Eukaryota) can be readily detected using standard molecular biological techniques. This indicates that environments on Mars that are similar in mineralogy may yet record a signature of life.
  • Advances in NanoSIMs method development for the analysis of the three isotopes of sulfur reveal a clear signature of an anoxic Neoarchean atmosphere at spatial scales of less than a micron.
  • Micron scale 13-C analysis of graphite grains identified in the ancient Akilia QP lithology in Greenland reveal significant isotopic heterogeneity in sub-domains of single crystal graphite that may constitutue a biosignature.
  • Studies of Paleoproterozoic phosphorite deposits suggest that the rise in atmospheric oxygen around 2.5 Ga may have been due in part to an increased delivery in riverine phosphate at that time.

Highlights in the area of Astrobiological Flight Instrumentation Testing during the past year include the following:

  • This past summer a 40 member science and engineering team successfully performed in field simulations of analytical instrumentation destined to fly on future Mars missions.

In summary, our team’s recent research, including discoveries and characterization of new planetary systems, investigation of the fates of carbon and water on planetary building blocks and other worlds, elucidation of robust pathways for prebiotic organic synthesis, documentation of novel microbial metabolic strategies, evaluation of possible biosignatures, and development of new technologies for astrobiological exploration, inform the central questions of astrobiology. Taken together, these discoveries are changing our views of life’s origin and its possible distribution in the universe.