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2010 Annual Science Report

Carnegie Institution of Washington Reporting  |  SEP 2009 – AUG 2010

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 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 (2009-2010) include the following:

  • Using the radial velocity extrasolar planet search Paul Butler and colleagues have identified strong evidence for the existence of the first habitable planet in orbit around the M dwarf star Gliese 581.
  • The next generation, ultra-high resolution Planet Finding Spectrometers (PFS) have been built and tested revealing a major breakthrough in precision.
  • The CIW CAPSCam-S instrument designed for astrometric searches for planetary systems meets specifications and is on the verge of yielding a steady stream of astrometric measurements of the dynamics of late M dwarf stars and any very low mass companions.
  • The Neptune Trojan survey is now complete providing crucial information regarding the formation of planetesimals. Analysis of the size distribution indicates that planetesimal formation proceeded directly from small to large objects.
  • Studies of circumstellar disks around young stars with high resolution optical spectroscopy leads to the discovery of an unusual binary star that is still accreting matter even after 12 Myr of formation.
  • Analysis of Oort cloud objects reveal ultra-red surfaces relative to comets in Halley-like periods and inclinations suggesting that these objects either came from a different region of the Oort cloud or have been recently thermally modified.
  • Analysis of new fragments of the Tagish lake meteorite reveal wide ranges in H/C and D enrichments (~ 1000 permil) that appear to correlate with the degree of aqueous alteration in the Tagish lake parent body.
  • FTIR analysis of organic solids from chondrites of varying class, group, and type reveal that amongst the thermally metamorphosed chondrites differences in molecular structure likely records differences in environmental conditions during metamorphism of the planetesimal.
  • Studies of planet formation reveal a “sweet spot” for efficient growth of large planets several astronomical unites from a star.
  • The Sun’s photosphere appears depleted in refractory elements relative to other Sun-like stars possibly indicating that other Sun-like stars never formed terrestrial/rocky planets.
  • New information about the planet Mercury is derived from the MESSENGER mission flybys.
  • Experiments reveal that the solubility of volatiles (CHON) in silicate melts is a strong function of the activity of oxygen, where universally solubility goes up as systems become more reducing.
  • Re-evaluation of the water content of the Martian interior reveals four times the water content previously thought. Mar’s water content is in the same magnitude for estimates of Earth’s interior.
  • New analyses reveal that the Moon, while much drier than the Earth or Mars, did contain significant amounts of water in its interior.
  • Detailed studies of diamonds and mineral inclusions in diamond shed light onto the evolution of continents.
  • Changes in the mineral distribution within shales strongly correlates with changes in atmospheric chemistry over many 100s of millions of years.
  • Transition metal sulfide minerals, e.g. ZnS, catalyze the formation of simple peptides from amino acids in dilute solutions in the absence of condensation reagents.
  • Studies of microbial biofilms living in deep sea hydrothermal vents reveals dominance by a single archeal phylotype that is capable of sustaining multiple metabolic pathways.
  • Gypsum dune environments on Earth, plausibly relevant to the surface of Mars, harbor active microbial communities in spite of the restricted nutrient supplies.
  • Analysis of Paleozoic arthropod fossils using Scanning Transmission X-ray Microscopy reveals molecular evidence for the extensive preservation of chitin-protein complex back to 410 Ma.
  • Instruments designed for Mars Science Laboratory and ExoMars were tested on Svalbard Island Norway, a Mars analog site.