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Project Reports

• Cosmic Distribution of Chemical Complexity

  This project explores the connections between chemistry in space and the origin of life. It is comprised of three tightly interwoven tasks. We track the formation and evolution of chemical complexity in space starting with simple carbon-rich molecules such as formaldehyde and acetylene. We then move on to more complex species including amino acids, nucleic acids and polycyclic aromatic hydrocarbons. The work focuses on carbon-rich species that are interesting from a biogenic perspective and on understanding their possible roles in the origin of life on habitable worlds. We do this by measuring the spectra and chemistry of analog materials in the laboratory, by remote sensing with small spacecraft, and by analysis of extraterrestrial samples returned by spacecraft or that fall to Earth as meteorites. We then use these results to interpret astronomical observations made with ground-based and orbiting telescopes.

  ROADMAP OBJECTIVES: 2.1 2.2 3.1 3.2 3.4 4.3 7.1 7.2

• Biosignatures in Ancient Rocks – Kasting Group

  The work by Ramirez concerned updating the absorption coefficients in our 1-D climate model. Harman’s work consisted of developing a 1-D code for modeling hydrodynamic escape of hydrogen from rocky planets.

  ROADMAP OBJECTIVES: 1.1 3.2 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Disks and the Origins of Planetary Systems

  This task is concerned with the evolution of complex habitable environments. The planet formation process begins with fragmentation of large molecular clouds into flattened disks. This disk is in many ways an astrochemical “primeval soup” in which cosmically abundant elements are assembled into increasingly complex hydrocarbons and mixed in the dust and gas within the disk. Gravitational attraction among the myriad small bodies leads to planet formation. If the newly formed planet is a suitable distance from its star to support liquid water at the surface, it is in the so-called “habitable zone.” The formation process and identification of such life-supporting bodies is the goal of this project.

  ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 4.1 4.3

• Project 3: Impact History of the Earth-Moon System

  The influx of interplanetary debris onto the early Earth represents a major hazard to the emergence of life. Large crater-forming bodies must have been common in the early solar system, as craters are seen on all ancient solid surfaces from Mercury to the moons of the outer planets. Impact craters are few in number on the Earth today only because geologic activity and erosion gradually erase them. The Earth’s nearest neighbor, the Moon, lacks an atmosphere and significant tectonic activity, and therefore retains a record of past impacts. The goal of our research is to reconstruct the bombardment history of the Moon, and by proxy the Earth, to establish when the flux of sterilizing impacts declined sufficiently for the Earth to became habitable.

  ROADMAP OBJECTIVES: 4.3

• Project 4: Survival of Sugars in Ice/Mineral Mixtures on High Velocity Impact

  Understanding the delivery and preservation of organic molecules in meteoritic material is important to understanding the origin of life on Earth. Though we know that organic molecules are abundant in meteorites, comets, and interplanetary dust particles, few studies have examined how impact processes affect their chemistry and survivability under extreme temperatures and pressures. We are investigating how impact events may change the structure of simple sugars, both alone and when combined with ice mixtures. The experiments will allow us to understand how sugar chemistry is affected by high pressure events and to contrast the survival probabilities of sugars in meteorite and comet impacts. This will lead to a better understanding of how organic molecules are affected during their delivery to Earth. This project leverages expertise in two different NAI nodes, increasing collaborative interaction among NAI investigators.

  ROADMAP OBJECTIVES: 1.1 3.1 4.1 4.3

• Biosignatures in Extraterrestrial Settings

  We are working on finding potentially habitable extrasolar planets, using a variety of search techniques, and developing some of the technology necessary to find and characterize low mass extrasolar planets. We also work on modeling and numerical techniques relevant to the problem of identifying extrasolar sites for life, and on some aspects of the prospects for life in the Solar System outside the Earth. The ultimate goal is to find signatures of life on nearby extrasolar planets.

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 4.1 4.3 6.2 7.1 7.2

• Early Animals: The Origins of Biological Complexity

  The fossil record provides the best evidence for the emergence of complex life and its relationship to changes in the environment. But this record is increasing supplemented by comparative studies of the development of living animals. Our group has been working on both the fossil record of some of the oldest fossil evidence of animals, as well as applying studies of the development of modern animals to interpret these fossils. The goal is to understand the interactions between changes in the physical environment, ecological interactions and in developmental mechanisms in evolutionary innovations leading to greater biological complexity.

  ROADMAP OBJECTIVES: 4.1 4.2 4.3

• Evolution of Protoplanetary Disks and Preparations for Future Observations of Habitable Worlds

  The evolution of protoplanetary disks tells the story of the birth of planets and the formation of habitable environments. Microscopic interstellar materials are built up into larger and larger bodies, eventually forming planetesimals that are the building blocks of terrestrial planets and their atmospheres. With the advent of ALMA, we are poised to break open the study of young exoplanetesimals, probing their organic content with detailed observations comparable to those obtained for Solar System bodies. Furthermore, studies of planetesimal debris around nearby mature stars are paving the way for future NASA missions to directly observe potentially habitable exoplanets.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3 7.2

• Biosignatures in Relevant Microbial Ecosystems

  PSARC is investigating microbial life in some of Earth’s most mission-relevant modern ecosystems. These environments include the Dead Sea, the Chesapeake Bay impact structure, methane seeps, ice sheets, and redox-stratified Precambrian ocean analogs. We target environments that, when studied, provide fundamental information that can serve as the basis for future solar system exploration. Combining our expertise in molecular biology, geochemistry, microbiology, and metagenomics, and in collaboration with some of the planet’s most extreme explorers, we are deciphering the microbiology, fossilization processes, and recoverable biosignatures from these mission-relevant environments.

  PSARC Ph.D. (now postdoctoral researcher at Caltech) Katherine Dawson published a new paper documenting the anaerobic biodegradation of organic biosignature compounds pristane and phytane. PSARC Ph.D. Daniel Jones (now postdoctoral researcher at U. Minnesota) published a new paper that uses metagenomic data to show how sulfur oxidation in the deep subsurface environments may contribute to the formation of caves and the maintenence of deep subsurface microbial ecosystems. PSARC Ph.D. student Khadouja Harouaka published a new paper that represents some of the first available information about possible Ca isotope biosignatures. Lastly, the Macalady group published a paper showing how ecological models based on available energy resources can be used to predict the distribution of microbial populations in space and time.

  ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2

• Project 6: The Environment of the Early Earth

  This project involves the development of capabilities that will allow scientists to obtain information about the conditions on early Earth (3.0 to 4.5 billion years ago) by conducting chemical analyzes of crystals (minerals) that have survived since that time. Minerals incorporate trace concentrations of ions and gaseous molecules from the local environment. We are conducting experiments to calibrate the uptake of these “impurities” that we expect to serve as indicators of temperature, moisture, oxidation state and atmosphere composition. Our focus has been mainly on zircon, quartz, and apatite.

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• Habitable Planet Formation and Orbital Dynamical Effects on Planetary Habitability

  The VPL explores how variations in orbital properties affects the growth, evolution and habitability of planets. The formation process must deliver the appropriate ingredients for life to a planet in order for it to become habitable. After planets form, interactions between a habitable planet at its host star and/or other planets in the system can change planetary properties, possibly rendering the planet uninhabitable. The VPL models these processes through computer models in order to understand how the Earth became and remains habitable, as well as examining and predicting habitability on planets outside the Solar System.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3

• Fundamental Properties Revealed by Parent Volatiles in Comets

  We detected prebiotic molecules in the atmosphere of the distant comet C/2006 W3 (Christensen), which has spent its entire orbital period well outside the zone of active water sublimation. We also integrated our spectral-spatial measurements of H₂O emission in comet 73P/ Schwassmann-Wachmann 3B with state-of-the-art 3D physical models of the inner cometary atmosphere, leading to new insights on a previously unidentified heating of coma gas from vaporizing icy grain mantles. And, we published a fluorescence model needed to interpret emission from deuterated methane released from cometary nuclei. These projects aim at improved understanding of cometary chemistry – a test bed for the contribution of comets to the delivery of exogenous prebiotic organics and water to early Earth, hypothesized as a precursor event to the emergence of the biosphere.

  ROADMAP OBJECTIVES: 2.2 3.1 4.3

• Molecular Biosignatures: Reconstructing Events by Comparative Genomics

  Reconstructing ancient events in genome evolution provides a valuable narrative for planetary history. Phylogenetic analysis of protein families within microbial lineages can be used to detect horizontal gene transfers and the evolution of new metabolic pathways and physiologies, many of which are significant in reconstructing ancient ecologies and biogeochemical events. These gene transfers can also be used to constrain molecular clock models for early life evolution, applying principles of stratigraphy and date calibration. A better understanding of gene evolution, including partial horizontal gene transfer, is needed to improve these inferences and avoid systematic errors.

  ROADMAP OBJECTIVES: 3.2 3.4 4.1 4.2 4.3 5.1 5.2 6.1

• The Astrobiology Walk

  The Goddard Center for Astrobiology (GCA) has completed the development and installation of a permanent outdoor exhibit at the Goddard Space Flight Center (GSFC) Visitor Center as a major public outreach effort. The “Astrobiology Walk” is designed to showcase the latest scientific discoveries from the GCA research theme “Search for the Origin and Evolution of Organics” in the context of a timeline for the evolution of the Universe and the Solar System. The exhibit consists of ten outdoor stations situated on the circular pathway around the Visi-tor Center’s “Rocket Garden”, each with a memorable iconic 3D object to convey the main scientific message. QR codes link each placard to web sites relevant to that topic.

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 4.1 4.3 7.1 7.2