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Project Reports

• Biosignatures in Ancient Rocks – Kasting Group

  We have been working on two things: 1) the question of whether there are plausible “false positives” for life on extrasolar planets, i.e., high abiotic O2 and/or O3 levels that might be confused with evidence for photosynthesis, and 2) hydrodynamic escape of hydrogen from H2- or H2O-rich primitive atmospheres. We are developing a two-component model to describe this process. Old single-component models evidently do not obey the diffusion limit, so are are trying to remedy that.

  ROADMAP OBJECTIVES: 1.1 2.1 4.1 7.2

• Co-Crystals on the Surface of Titan

  We have discovered that benzene and ethane form a co-crystalline inclusion compound at Titan surface temperatures and pressures. Co-crystals of other organic compounds could be common on Titan’s surface. These results can help explain the release of ethane observed at the Huygens landing site, and point to a new type of surface material that may have significant impact on Titan surface chemistry and geology.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• 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

• Project 1: Interstellar Origins of Preplanetary Matter

  Interstellar space is rich in the raw materials required to build planets and life, including essential chemical elements (H, C, N, O, Mg, Si, Fe, etc.) and compounds (water, organic molecules, planet-building minerals). This research project seeks to characterize the composition and structure of these materials and the chemical pathways by which they form and evolve. The long-term goal is to determine the inventories of proto-planetary disks around young sun-like stars, leading to a clear understanding of the processes that led to our own origins and insight into the probability of life-supporting environments emerging around other stars.

  ROADMAP OBJECTIVES: 1.1 3.1

• Development of Direct Sampling Methodology for Analysis of Complex Organic Mixtures on Titan’s Surface

  Photochemistry in Titan’s dense atmosphere generates a complex mixture of organic molecules that have been deposited on Titan’s surface over time. Requiring no sample pretreatment or handling, the technique of direct analysis in real time (DART), combined with an ion trap mass spectrometer having MS/MS capability, is shown to be an enabling experimental methodology to vaporize, ionize, and structurally characterize organic components of this mixture. A key important development is the use of temperature programmed desorption, accomplished by heating of the probe gas, to examine complex mixtures of organics with a wide range of volatility (polypropylene glycol and tar samples from a petroleum seep). Of particular relevance to astrobiology, this methodology is employed to compare Titan simulants produced in a pulsed discharge from gas mixtures designed to probe mechanistic pathways leading to high molecular weight products.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• Project 2: Cells as Engines and the Serpentinization Hypothesis for the Origin of Life

  All life is, and must be, “powered” since all of its most essential and distinguishing processes have to be driven “up-hill” against their natural thermodynamic direction. By the 2nd law of thermodynamics, however, a process can only be made to proceed up-hill by being mechanistically linked, via a molecular device functioning as an engine, to another, more powerful, process that is moving in its natural, down-hill direction. On fundamental principles, we argue, such engine-mediated conversion activities must also have been operating at, and indeed have been the cause of, life’s emergence. But what then were life’s birthing engines, what sources of power drove them, what did they need to produce, and how did they arise in an entirely lifeless world? Promising potential answers to these and other questions related to the emergence of life are provided by the Alkaline Hydrothermal Vent/serpentinization (“AHV”) hypothesis, whose original propounder and lead proponent, Dr. Michael Russell of JPL, is a co-investigator on this project. The goal of the project is specifically to clarify the essential mechanistic modus operandi of all molecular engines that power life, and to see how the most fundamental and prerequisite of these could have arisen, and operated, in the structures and flows produced by the serpentinization process. Importantly, candidate answers to these questions can be put to definitive laboratory tests.

  ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 3.3 3.4

• Astrophysical Controls on the Elements of Life – Task 4 – Model the Injection of Supernova Material Into Protoplanetary Disks

  The goal of this project has been to determine whether supernova material could be injected into a protoplanetary disk, the disk of gas and dust from which planets form. A secondary issue is whether these materials would be mixed within the disk efficiently, and whether such an injection into our own protoplanetary disk can explain the isotopic evidence from meteorites that the solar system contained short-lived radionuclides like ²⁶Al.

  ROADMAP OBJECTIVES: 1.1 3.1

• Biosignatures in Ancient Rocks – Kump Group

  We are analyzing FAR-DEEP cores that span the putative “oxygen overshoot” associated with the termination of the Great Oxidation Event, 2.0 billion years ago. The volcanic rocks in question are highly oxidized. Our hypothesis is that oxygen-enriched groundwaters altered these rocks during a time interval when atmospheric oxygen concentrations approached modern levels, falling subsequently to lower values characteristic of the ensuing billion years. Kump has also proposed a new explanation for the “second rise of atmospheric oxygen” in the Neoproterozoic (ca. 850 Ma).

  ROADMAP OBJECTIVES: 1.1 4.1 4.2 4.3 5.2 6.1

• 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 2: Processing of Precometary Ices in the Early Solar System

  The discovery of numerous planetary systems still in the process of formation gives us a unique opportunity to glimpse how our own solar system may have formed 4.6 billion years ago. Our goal is to test the hypothesis that the building blocks of life were synthesized in space and delivered to the early Earth by comets and asteroids. We use computers to simulate shock waves and other processes that energize the gas and dust in proto-planetary disks and drive physical and chemical processes that would not otherwise occur. Our work seeks specifically to determine (i) whether asteroids and comets were heated to temperatures that favor prebiotic chemistry; and (ii) whether the requisite heating mechanisms operate in other planetary systems forming today.

  ROADMAP OBJECTIVES: 1.1 3.1 3.2

• Biosignatures in Ancient Rocks – Ohmoto Group

  This project has been aimed at understanding the chemical and biological natures of the ocean-atmosphere-lithosphere systems during the Archean. A second objective is testing a hypothesis that the MIF-S isotope signatures, which characterize some Archean and younger sedimentary rocks, were generated during reactions between hydrothermal fluids and organic-rich sediments, rather than through atmospheric reactions.

  ROADMAP OBJECTIVES: 1.1 4.1 6.1

• Circumstellar Debris and Planetesimals in Exoplanetary Systems

  This year, GCA astronomer Marc Kuchner invited the public to help him discover new planetary systems through a new website, DiskDetective.org. At DiskDetective.org, volunteers view data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission and three other surveys. WISE measured more than 745 million objects, representing the most comprehensive survey of the sky at mid-infrared wavelengths ever taken.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1

• Coupled Energy Balance Ecosystem-Atmosphere Modeling of Thermodynamically-Constrained Biogenic Gas Fluxes Project

  The thermodynamically-constrained fluxes of gases to and from a biosphere has profound, planet-wide consequences. These fluxes can directly control the redox state of the surface environment, the atmospheric composition, and the concentration of nutrients and metals in the oceans. Through these direct effects, they also create strong forcings on the climate, the redox state of the interior of the planet, and the detectability of the biosphere by remote observations. This is a theoretical modeling study to constrain biomass, productivity, and biogenic gas fluxes given a range of geologic parameters.

  ROADMAP OBJECTIVES: 1.1 1.2 5.2 5.3 6.1 7.2

• Astrophysical Controls on the Elements of Life – Task 5 – Model the Variability of Elemental Ratios Within Clusters

  We carried out studies of self-enrichment of the earliest star clusters. Building on the turbulence simulations in Pan & Scannapieco (2010) and Pan et al. (2011), we examined the mixing of heavy elements generated by stars into the surrounding cluster environments.

  ROADMAP OBJECTIVES: 1.1 3.1

• Astrophysical Controls – Task 6 – Determine Which Elemental or Isotopic Ratios Correlate With Key Elements

  Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. We study the formation and composition of structures in supernova explosions that deliver isotopes that influence habitability to material that will form new stars and planets. We examine ratios of elements that have substantial effects of the mineralogy and interiors of planets. The relative abundances of common elements vary substantially among nearby stars, and we find that the impact of this on a star’s evolution can change the amount of time its planets are habitable by large factors.

  ROADMAP OBJECTIVES: 1.1 3.1

• Longer Wavelength Photochemistry of Condensates and Aerosols in Titan’s Lower Atmosphere and on the Surface

  This study focuses on the condensed phase photochemistry on Titan. In particular, we focus on understanding longer wavelength photochemistry of solid hydrocarbons so simulate photochemistry that could occur based on the UV penetration through the atmosphere and on the evolution of complex organic species in astrobiologically significant regions on Titan’s surface. Here we investigate the oxygenation chemistry involving the condensed Titan’s organic aerosols with water-ice on Titan’s surface – induced by high energy photons simulating the cosmic ray induced chemistry on Titan’s surface.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2 3.3

• Comets as Keys to Solar System Formation

  Comets are both a key indicator of the processes that formed the early Solar System and potentially a source of volatiles and organics needed to make habitable planets. In this work we investigate how modern theories of planet and planetesimal formation may lead to predicted signatures in comets and, when compared with real comets, to tests of those theories.

  ROADMAP OBJECTIVES: 1.1 2.2

• 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

• 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

• Project 5: 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 performing chemical analyzes of crystals (minerals) that have survived since that time. When they grow, 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. To date, our focus has been mainly on zircon (ZrSiO₄), but we have recently turned our attention to quartz as well.

  ROADMAP OBJECTIVES: 1.1 4.1

• Astrophysical Controls – Task 7 – Update Catalog of Elemental Ratios in Nearby Stars

  Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. Elemental ratios can change the stellar evolution and mineralogy, geophysics, and surface processed of planets. We study the abundances of large samples of nearby stars and individual systems and the extent of their variation. We examine ratios of elements that have substantial effects of the mineralogy and interiors of planets. The relative abundances of common elements vary substantially among nearby stars. Extremely non-solar abundance ratios at the level that can produce substantial changes in planetary and stellar properties are present in interesting numbers.

  ROADMAP OBJECTIVES: 1.1 7.2

• NAI Titan Education and Public Outreach

  Planetariums have a long history of experimentation with audio and visuals to create new multimedia experiences. We report on a series of innovative experiences that began in the Gates Planetarium at the Denver Museum of Nature & Science, combining live performances of music and navigation through scientific visualizations. The Life Out There productions featured a story showcasing astrobiology concepts at scales ranging from galactic to molecular, and told using VJ-ing of immersive visualizations and musical performances from the House Band of the Universe. These hour-long shows were broken into four separate themed musical movements, with an improvisatory mix of music, dome visuals, and spoken science narrative which resulted in no two performances being exactly alike. Post-performance dissemination is continuing via a recorded version of the performance available as a DVD and online streaming video. Written evaluations from visitors who were present at the live shows reveal high satisfaction and subsequent interest in astrobiology topics. Life Out There concerts have been used to inaugurate a new evening program to draw in a younger audience demographic to DMNS, and have been taken on the road to other venues in other cities.

  We continued the development and public presentation of this live digital planetarium show about Titan and Astrobiology. This live lecture planetarium show, entitled “Life Out There” makes use of the digital imaging capabilities of the dome, through the innovative Uniview software, a “real time” virtual simulation of the known universe based on accurate astronomical databases and modeling. The inclusion of live musicians, who serve to introduce each section of the show, helps to attract an audience beyond those who reliably come to space science events at the planetarium, and help to create a relaxing and evocative atmosphere conducive to wonder and learning. With Uniview, we can utilize the SPICE Kernels that spacecraft teams use to describe mission trajectories, and create virtual versions that can be followed along through the simulation. Using 3-D spacecraft models, the public can follow spacecraft missions shown with breathtaking realism within the immersive display. We have a detailed model of the Cassini spacecraft, and we are using the most recently updated SPICE kernels of Cassini, including the many Titan flybys, to show the public the fantastic journey of Cassini and Huygens in exploring Titan. In addition to the live lecturer, a second operator controls the Uniview software, allowing these flybys to be seen from any perspective deemed instructive and/or entertaining. Various Cassini and Huygens image data sets, including camera data, infrared spectrometer data and radar data, are being texture mapped and rendered on the moon’s surface. The atmosphere is visually peeled away, and various visuals are used together with an original script and musical score, both written by E/PO lead David Grinspoon, to explore themes of Titan and Astrobiology for the public. The visual content was directed by Dr. KaChun Yu, Curator of Space Sciences at DMNS, in collaboration with Dr. Grinspoon.

  We developed, tested, evaluated and disseminated a 20-minute stage show for informal science centers to excite and inform visitors about the science and exploration of Titan. The show utilizes a participatory exercise in scientific illustration to engage visitors in the material. Each participant is given a clipboard and pencils, and the facilitator, using a series of Cassini and Huygens images and videos of Titan, leads them through an exercise in which each draws a sketch of a Titan landscape, learning along the way about many aspects of the Titan environment as revealed by modern exploration. The show has now been seen by many thousands of visitors to the Denver Museum of Nature and Science.

  During this last year we focused on disseminating the presentation materials and supporting media, and training materials, including a training DVD for presenters for use at other informal science centers.

  We continued the development and public presentation of a live digital planetarium show about Titan and Astrobiology. This live lecture planetarium show, entitled “Life Out There” makes use of the digital imaging capabilities of the dome, through the innovative Uniview software, a “real time” virtual simulation of the known universe based on accurate astronomical databases and modeling. The inclusion of live musicians, who serve to introduce each section of the show, helps to attract an audience beyond those who reliably come to space science events at the planetarium, and help to create a relaxing and evocative atmosphere conducive to wonder and learning. With Uniview, we can utilize the SPICE Kernels that spacecraft teams use to describe mission trajectories, and create virtual versions that can be followed along through the simulation. Using 3-D spacecraft models, the public can follow spacecraft missions shown with breathtaking realism within the immersive display. We have a detailed model of the Cassini spacecraft, and we are using the most recently updated SPICE kernels of Cassini, including the many Titan flybys, to show the public the fantastic journey of Cassini and Huygens in exploring Titan. In addition to the live lecturer, a second operator controls the Uniview software, allowing these flybys to be seen from any perspective deemed instructive and/or entertaining. Various Cassini and Huygens image data sets, including camera data, infrared spectrometer data and radar data, are being texture mapped and rendered on the moon’s surface. The atmosphere is visually peeled away, and various visuals are used together with an original script and musical score, both written by E/PO lead David Grinspoon, to explore themes of Titan and Astrobiology for the public. The visual content was directed by Dr. KaChun Yu, Curator of Space Sciences at DMNS, in collaboration with Dr. Grinspoon.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• Exploring the Structure and Composition of Massive Exoplanets

  We have analyzed exoplanet transit and eclipse measurements with the Hubble Space Telescope (HST) and the Spitzer Space Telescope for a number of highly irradiated, Jupiter-mass planets, with a focus on confirming which planets exhibit water absorption or emission in transit and/or eclipse and measuring the characteristic brightness temperature at these wavelengths. Measurements of molecular absorption in the atmospheres of these planets offer the chance to explore several outstanding questions regarding the atmospheric structure and composition of hot Jupiters, including the possibility of bulk compositional variations between planets and the presence or absence of a stratospheric temperature inversion. We are also developing simulations of future observations with the James Webb Space Telescope, and we are in the process of designing a future balloon-borne telescope to conduct a large survey of hot exoplanet atmospheres.

  ROADMAP OBJECTIVES: 1.1 1.2 7.2

• Astrophysical Controls on the Elements of Life, Task 1: High-Precision Isotopic Studies of Meteorites

  ROADMAP OBJECTIVES: 1.1 3.1

• 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

• Habitable Planet Formation and Orbital Dynamical Effects on Planetary Habitability

  This task explores how habitable planets form and how their orbits evolve with time. Terrestrial planet formation involves colliding rocks in a thin gaseous disk surrounding a newborn star and VPL’s modeling efforts simulate the orbital and collisional evolution of a few to millions of small bodies to determine the composition, mass and orbital parameters of planets that ultimately reach the habitable zone. After formation, gravitational interactions with the star and planet can induce short- and long-term changes in orbital properties that can change available energy to drive climate and illuminate the planetary surface. The VPL simulates these effects in known and hypothetical planetary systems in order to determine the range of variations that permit planetary habitability.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3

• 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

• Fingerprinting Late Additions to the Earth and Moon via the Study of Highly Siderophile Elements in Lunar Impact Melt Rocks

  During this funding cycle we completed work on abundances of highly siderophile elements (HSE) and Os isotopes in Apollo 17 impact melt rocks. The results were woven into a manuscript by UMd Ph.D. student Miriam Sharp. The resulting large database for impact melt rocks from this site is consistent with a dominant signature imparted to rocks from a single major impactor. The inferred composition of this impactor was broadly chondritic with respect to HSE, but characteristically enriched in ¹⁸⁷Os/¹⁸⁸Os (proxy for long-term Re/Os), Ru/Ir and Pd/Ir, relative to most chondrites that have been analyzed for these elements. The characteristics of the dominant impactor are most similar to chondritic meteorites that are relatively poor in organics and volatiles (e.g., enstatite chondrites), and so the formation of the spatially associated Serenitatis basin was likely not a process that delivered substantial water and/or organics to the lunar crust. These results were published in Sharp et al. (2014).

  ROADMAP OBJECTIVES: 1.1

• Habitability of Water-Rich Environments, Task 2: Model the Dynamics of Icy Mantles

  One of Jupiter’s moons, Europa, is one of the few places in the solar system in which the physical and chemical conditions may be suitable for sustaining life. Europa is composed on an outer H2O layer, comprised of rigid ice overlying a liquid water ocean. It is this liquid water ocean which has been hypothesized as having the ingredients necessary for life, but it is shielded from our observation by the thick ice layer. However, under certain conditions, the ice layer is expected to undergo convection, possibly transporting chemicals from the liquid ocean to the surface, where we may be able to detect them. We perform computer modeling of ice/ocean convection to investigate how ocean material is carried up through the ice layer and whether it is expected to reach Europa’s surface. This work provides guidance for future missions which may probe the chemistry of the ice surface.

  ROADMAP OBJECTIVES: 1.1 2.2

• Planetary Surface and Interior Models and SuperEarths

  We use computer models to simulate the evolution of the interior and the surface of real and hypothetical planets around other stars. Our goal is to determine the initial characteristics that are most likely to contribute to making a planet habitable in the long run. Observations in our own Solar System show us that water and other essential materials are continuously consumed via weathering (and other processes: e.g., subduction, sediment burial) and must be replenished from the planet’s interior via volcanic activity to maintain a biosphere. The surface models we are developing will be used to predict how gases and other materials will be trapped through weathering and biological processes over time. Our interior models are designed to predict tidal effects, heat flow, and how much and what sort of materials will come to a planet’s surface through resurfacing and volcanic activity throughout its history.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1

• Fischer-Tropsch-Type Reactions in the Solar Nebula

  Fischer-Tropsch-Type (FTT) reactions can form complex hydrocarbons via surface-mediated reactions using simple gases (CO, N₂, and H₂) on almost any grain surface and are currently being studied in relation to the early Solar Nebula. Several theories exist as to how hydrocarbons are formed in the early Solar System but the compelling nature of this type of reaction is that it is passive and generates a wide variety of complex hydrocarbons using commonly available components (gases/grains) without invoking a complex set of conditions for formation.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• Stellar Effects on Planetary Habitability and the Limits of the Habitable Zone

  In this task, VPL team members studied the interaction between stellar radiation (including light) and planetary atmospheres to better understand the limits of planetary habitability and the effects of stellar radiation on planetary evolution. Work this year included using climate models to recalculate the boundaries of the surface liquid water habitable zone planets of different masses, an exploration of the effect of a star’s spectrum on the rate at which a planet can exit a snowball state, and calculation of water loss from terrestrial planets with different fractions of atmospheric carbon dioxide. Atmospheric escape models were also used to illustrate how the pre-main sequence evolution of M-dwarf stars could strip the gaseous envelopes from mini-Neptune planets, transforming them into potentially-habitable, Earth-sized rocky bodies. In pioneering work, VPL researchers also showed that the pre-main sequence phase of an M-dwarf can lead to strong atmospheric escape of water on otherwise potentially habitable worlds, potentially rendering them uninhabitable. Observational work was also undertaken to characterize the frequency and characteristics of stellar flares on M dwarf stars from Kepler data, as input to future work on characterizing the effect of stellar flares on habitability.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1

• NNX09AH63A Origin and Evolution of Organics in Planetary Systems

  The Blake group has been carrying out joint observational and laboratory programs with NAI node scientists on the water and simple organic chemistry in the protoplanetary disk analogs of the solar nebula and in comets. Observationally, we continue to build on our extensive (>100 disks) Spitzer IRS survey of the infrared molecular emission from the terrestrial planet forming region of disks with follow-up work using the high spectral resolution ground-based observations of such emission (via the Keck and the Very Large Telescopes, the Herschel Space Observatory, SOFIA, and ALMA) along with that from comets. This year, we emphasized disk studies with the rapidly maturing capabilities of the ALMA observatory, that promises to revolutionize our understanding of the formation and migration of protoplanets, and with infrared studies of the molecular volatiles detectable in both comets and exoplanetary atmospheres. In the lab, we have continued to exploit our novel approach to broad-band chirped pulse microwave spectroscopy that promises to drop the size, mass and cost of such instruments by one to two orders of magnitude, and have developed a decade-spanning THz frequency comb with unprecedented precision. We are using these new instruments to measure the rotational spectra of prebiotic compounds, along with a detailed characterization of their large amplitude vibrations. Looking forward, these techniques have the potential to make site-specific stable isotope measurements, a capability we will continue to explore with GSFC Node scientists.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1

• Understanding Past Earth Environments

  This year, this interdisciplinary effort continued on two major fronts. First, we furthered the development and use of new techniques that help us characterize environmental conditions on ancient Earth. This included progress on our development of a technique for estimating the atmospheric pressure on Archean Earth, and the development and use other techniques for analyzing the chemistry of Archean lakes. We also used our existing models of ancient Earth to simulate other conditions consistent with the conclusions reached from these laboratory analyses.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1

• Understanding the Early Mars Environment

  In this task VPL team members use Mars mission data and atmospheric models to understand the early environment on Mars. Areas of research include: the atmospheric formation of salts that have been found on the Martian surface, Early Mars volcanism and atmospheric composition, and possible atmospheric means of warming early Mars. Several VPL team members are also active on the MSL mission and have contributed to scientific discussions of modern geochemistry and the ancient habitability of Mars.

  ROADMAP OBJECTIVES: 1.1 2.1

• 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

• Project 3A: Searching for Ancient Impact Events Through Detrital Shocked Zircons

  Understanding how quickly planetary surface environments evolve on newly accreted worlds is critical for predicting when habitable conditions are established. The meteorite impact history of the inner solar system strongly indicates that the Earth was subject to a global impact bombardment during the first few hundred million years after accretion. The scope, timing, and consequences of this profound process are hotly debated. This project investigated populations of detrital zircons in Archean sedimentary rocks to search for tell-tale signs of impact processes in the form of shock-induced microstructures that are diagnostic of impact. Such features have been shown to survive in detrital shocked zircons eroded from known impact structures on Earth, including the Vredefort, Sudbury, and Santa Fe craters. We have investigated populations of 1,000 zircons per sample using backscattered electron imaging of grain exteriors with a scanning electron microscope. Thus far we have surveyed zircons separated from rocks collected from the Yilgarn craton (Australia), North China craton (China), Wyoming craton (USA), and the Superior craton (Canada). While intriguing microstructures have been observed, thus far no confirmed shock microstructures have been encountered. Our inability the identify shocked grains in populations of 1,000 zircons (per sample) does not necessarily mean shocked grains are absent; our results provide constraints that if they are present, they are in abundances of <0.1% in the detrital population of the rocks investigated. Our detailed search continues…

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• 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

• Undergraduate Research Associates in Astrobiology (URAA)

  In 2014, the Goddard Center for Astrobiology (GCA) hosted the tenth session of our summer program for talented science students (Undergraduate Research Associates in Astrobiology), a ten-week residential research program tenured at Goddard Space Flight Center and the University of Maryland, College Park (http://astrobiology.gsfc.nasa.gov/education.html). Competition was very keen, with an oversubscription ratio of 3.0. Students applied from over 15 Colleges and Universities in the United States, and 2 Interns from 2 institutions were selected. Each Intern carried out a defined research project working directly with a GCA scientist at Goddard Space Flight Center or the University of Maryland. As a group, the Associates met with a different GCA scientist each week, learning about his/her respective area of research, visiting diverse laboratories and gaining a broader view of astrobiology as a whole. At summer’s end, each Associate reported his/her research in a power point presentation projected nation-wide to member Teams in NASA’s Astrobiology Institute, as part of the NAI Forum for Astrobiology Research (FAR) Series.

  ROADMAP OBJECTIVES: 1.1 3.1 6.2

• 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