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Project Reports

• 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

• Laboratory Investigations Into Chemical Evolution in Icy Solids From the Interstellar Medium to the Outer Solar System to Meteorites

  NAI-GCA support in 2014 helped us continue our work on amino-acid stability. In 2014, we performed radiation experiments to measure the destruction rate of glycine in CO₂ ice. In particular, we found that this rate depends on concentration and temperature, and is 20-40 times greater than for glycine in H₂O-ice.

  ROADMAP OBJECTIVES: 2.1 2.2 3.1 7.1 7.2

• Long-Term Variation of High Energy Activity of Young Stars in Mass Accretion Outburst and Quiescence

  High-energy photons in the young stellar environment are known to stimulate chemical reactions of molecules, producing prebiotic materials that might later be incorporated into comets and through them into young planets. Observational tests are sorely needed to assess the significance of such processing for Astrobiology, and to guide development of theoretical models for chemical evolution in protoplanetary environments.

  ROADMAP OBJECTIVES: 2.2 3.1

• 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

• 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

• 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

• 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

• 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

• The Evolution of Organics in Space

  The molecular heritage of our Solar System stretches back to the interstellar cloud from which it formed. Knowledge of the chemistry of this cloud is crucial to understanding the process of star and planet formation; this is part of the field of astrochemistry. Since much of astrochemistry deals with the organic molecules found in space and in solar system environments, astrochemistry itself may be considered part of the larger field of astrobiology. The present project includes both observations of these organic molecules and participating in the preparation of an Encyclopedia of Astrobiology.

  ROADMAP OBJECTIVES: 3.1

• Volatile Composition of Comets: Emphasis on Oxidized Carbon

  DiSanti’s research emphasizes the chemistry of volatile oxidized carbon in comets, in particular the efficiency of converting CO to H₂CO and CH₃OH through reduction reactions on the surfaces of icy grains prior to their incorporation into the cometary nucleus. Additionally, oxidation reactions on grains can play a significant role, particularly for CO-enriched, C₂H₂-depleted comets such as C/2009 P1 (Garradd; see item 1 under Section 3 below). Such processes produce precursor molecules that (if delivered to Earth through impact of comet nuclei) could have enabled the emergence of life, and so are highly relevant to Astrobiology.

  ROADMAP OBJECTIVES: 3.1 3.2

• Advancing Techniques for in Situ Analysis of Complex Organics: Laser Mass Spectrometry of Planetary Materials

  In this final reporting period under CAN-5, we extended the development of protocols for laser mass spectrometry (MS) for analysis of complex, nonvolatile organic molecules from the progress made last year. In particular the major area of focus was in (1) the use of tunable laser wavelengths for desorption in two-step laser MS (L2MS), and (2) the use of tandem mass spectrometry (MS/MS) for in situ molecular structure analysis. Each of these protocols has been investigated during the course of the CAN-5 project, jointly supported by NAI and instrument development (PIDDP, MatISSE) and flight (MOMA) programs. The unique aspect of these efforts is their implementation and evaluation using truly miniature, flight-like instrumentation, to optimize the benefit to real mission science.

  ROADMAP OBJECTIVES: 2.1 2.2 3.2 7.1

• Analysis of Prebiotic Organic Compounds in Astrobiologically Relevant Samples

  The Astrobiology Analytical Laboratory (AAL) of the GCA is dedicated to the study of organic compounds derived from past and future sample return missions, meteorites, lab simulations of Mars, interstellar, protoplanetary, and cometary ices and grains, and instrument development. This year, we continued our work analyzing the organic content of carbonaceous chondrites, expanding beyond our previous amino acid and nucleobase analyses to determine distribution and abundances of pyridine carboxylic acids and aliphatic amines. We investigated the effects of cosmic ray irradiation on amino acids. We supported development of a liquid chromatographmass spectrometer aimed at in situ analyses of amino acids and chirality on airless bodies including asteroids and the outer planet’s icy moons Enceladus and Europa. We hosted an undergraduate and participated in numerous public outreach and education events. We continued our participation in the OSIRISREx asteroid sample return mission and provided support for the Sample Analysis at Mars instrument of NASA’s Mars rover Curiosity.

  ROADMAP OBJECTIVES: 2.1 3.1

• 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

• Fundamental Properties Revealed by Parent Volatiles in Comets

  We studied water and other prebiotic molecules in the atmospheres of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy). 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

• 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

• 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