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Executive Summary

The central goal of the Goddard Center for Astrobiology (hereafter, GCA), a member team of NASA’s Astrobiology Institute (NAI), is to understand how organic compounds are created, destroyed, and altered during the formation and evolution of a planetary system, leading up to the origin of life on a planet such as Earth. Planetary systems form by collapse of dense interstellar cloud cores. Some stages in this evolution can be directly observed when stellar nurseries are imaged, while other stages remain cloaked behind an impenetrable veil of dust and gas. Yet to understand the origin of life on Earth, we must first develop a comprehensive understanding of the formation of our own planetary system. The clues contained in the most primitive bodies from that formative era (comets and primitive meteorites) are central to advancing our understanding of that epoch and of later delivery of volatiles (water, prebiotic organics, etc.) to Earth. To assess and enhance the probability of finding life elsewhere we must understand both the similarities and differences between the evolution of our own system and those associated with other stars.

The central question of our research is: Did delivery of exogenous organics and water enable the emergence and evolution of life? Our proposed research addresses the heart of Goal 3 of the Astrobiology Roadmap: Understand how life emerges from cosmic and planetary precursors.

The GCA investigation is organized into four Themes:

Theme 1: Establish the taxonomy of icy planetesimals and their potential for delivering pre-biotic organics and water to the young Earth and other planets.
Theme 2: Investigate processes affecting the origin and evolution of organics in planetary systems, and the presence of organics on exoplanets.
Theme 3: Assess the formation, distribution, abundance, and isotopic composition of complex organics in authentic extraterrestrial samples through advanced laboratory analyses of them, and of products formed during laboratory simulations.
Theme 4: Develop advanced methods for the in-situ analysis of complex organics in small bodies in the Solar System.

This tenth year of our Astrobiology Program saw major emphasis on research collaborations across disciplines. GCA Team members conducted a vigorous and highly productive research program in all four Thematic areas. We conducted many investigations in the laboratory and in the field (mainly astronomical), as summarized below and in the individual Reports of progress.

Team members participated in numerous meetings and workshops, presenting scientific results there and in many papers in the scientific literature. Bibliographies of papers published in year ten are listed in the individual Reports.

In year eight, we initiated a conceptual design for the “Astrobiology Walk”, a new outdoor exhibit envisioned for the Goddard Visitors Center – and the first of its kind in the Western Hemisphere. That vision was realized by completing its installation in August 2013. The Walk features 10 stations that address key developments along the timeline leading from the Big Bang to the current status of life in our Planetary System, and the search for life in Exo-planetary Systems. Each station features two museum-quality placards, the first conveys the key development for that time step and the second conveys the manner in which GCA scientists address that topic. Each station also features an iconic 3-D tactile object, to enhance the experience for visitors – especially the sight-challenged – and a QR code to extend the visitor’s experience by visiting related websites. Targeting middle school students, but with thought given to visitors of all levels of sophistication, the Walk became an immediate “must see” exhibit. See our EPO report for additional details.

We again hosted gifted undergraduate students for a mentored research experience in astrobiology-related disciplines, under our tenth annual program that was oversubscribed by a factor of 4.5. The research summaries, students, and mentors are described in our Report on this program (Undergraduate Research Associates in Astrobiology).

In addition to planting these seeds for the future, GCA Team members made significant progress in meeting our scientific goals:

Major Research Accomplishments:

Highlights of GCA NAI research during year ten include the following:

From the Interstellar Medium to Planets

In laboratory investigations of the unstable interstellar molecule ketene (H2C=C=O), by Co-I Hudson and collaborators found that it is readily made from known cometary and interstellar organics (e.g., H₂O, C₂H₂) in both polar and apolar ices and, of equal interest, leads to predictions of larger organic products (Hudson & Loeffler 2013).

Co-I Charnley & collaborators performed studies aimed at understanding the origin of isotopic fractionation in star-forming cores, with particular emphasis on deuterium and ¹⁵N. They compared the predicted isotopic fractionation signatures of meteoritic amino acids and nanoglobules with that expected if they, or their precursor molecules, formed in the interstellar medium. They carried out observational studies of anions in interstellar clouds and modeled their effects in cometary comae.

Co-I G. A. Blake and collaborators demonstrated that circumstellar abundance profiles could be retrieved from even spatially and spectrally unresolved data (provided the lines span a significant range in excitation). They first applied it to extract profiles for water vapor in the disk surrounding the T Tauri star TW Hydrae, using data from the Keck, Spitzer and Herschel observatories (Zhang et al. 2013).

Co-I M. Kuchner led development of a new technique and a new code for modeling the collisions and dynamics of debris disks. Called “SMACK”, the code will help us interpret images of planetary systems to better understand how planetesimals transport material within young planetary systems (Nesvold, Kuchner et al. 2013).

Using far-infrared data from the Herschel Space Observatory, Co-I A. Roberge led a study of the unusual 49 Ceti debris disk which showed a surprising amount of carbon gas emission that may arise from destruction of exo-comets (Roberge et al. 2013).

Co-I Roberge presented the first spatial maps of CO sub-mm emission in the famous Beta Pictoris debris disk. These ALMA maps showed strong spatial CO clumps far from the star. The authors propose that the clumps of CO gas seen are coming from exo-comets trapped into resonance with an unseen giant exoplanet (Dent et al. 2014, in press).

Dust coming from planetesimals in extrasolar planetary systems (aka. exozodiacal dust) is likely to be the largest source of noise for future direct observations of habitable planets (further details in Roberge et al. 2012). Co-I Roberge is addressing this problem through her membership on the LBTI Key Science Team. LBTI is a NASA-funded instrument for the Large Binocular Telescope, with the primary science aim of probing for exozodiacal dust down to levels relevant for a New Worlds Mission.

Co-I A. M. Mandell and co-I L. D. Deming detected water from exoplanets using WFC3 on the Hubble Space Telescope. Mandell et al. 2013 searched three exoplanets in primary transit (WASP-12b, WASP-17b, and WASP-19b) for signs of water vapor and other molecules in their atmospheres, detecting water clearly in WASP-17b. Deming et al. 2013 searched HD 209458b and XO-1b, detecting water in both giant planets.

Formative Processes in our Proto-Planetary disk

In the Cosmic Ice Lab, Co-I Hudson and collaborators inaugurated a laboratory program to quantify spectral data needed to determine the amount of frozen organics present in the trans-Neptunian region of the Solar System and beyond. They first measured the spectral constants of amorphous and crystalline acetylene ice, showing that literature spectra of the amorphous phase are incorrect (Hudson et al. 2014). The program will lead to improved interpretations of the structural phases of ices on TNOs and in comet nuclei.

In the Cosmic Dust Lab, Co-I J. Nuth and collaborators N. Johnson and F. Feigelson investigated formation of complex hydrocarbons by surface-mediated reactions using simple gases (CO, N₂, and H₂) found in the early Solar Nebula. In 2013, they brought the multiple (10-set) Fischer-Tropsch-Type (FTT) laboratory system into full operation; several students assisted in setting up and running FTT experiments. Meghan McCarthy (URAA Fellow) systematically explored the similarities and, in greater depth, the differences between iron and magnetite as FTT catalysts through temperature and reaction cycles. She clearly demonstrated that the organic coating developed on the grains through FTT reactions served as a ‘better’ catalyst than did the original grain surface. Her findings provide a basis for further exploration, particularly that of possible amino acid formation, as well as testing whether the catalyst’s initial oxidation state may control the end-state reaction products.

Messengers from the Early Solar System – Comets

We opened a new chapter in understanding the chemical diversity among comets. A taxonomy based on the volatile composition of comet nuclei is emerging, but it is based mainly on more than 20 comets observed within the water-activated region (< 2 AU from the Sun). This opens the question: is the emergent taxonomy biased by water activation and chemical activity in the surface layer of the cometary nucleus? The question can be addressed by quantifying the coma composition of comets that are still far from the Sun where water ice is not active, but that are instead activated by release of hypervolatile gases. In this reporting period, we published first results from this program: the first multi-line detection of CO in the Centaur comet 29P/Schwassmann-Wachmann 1 at 6.2 AU for which water is never activated (Paganini et al. 2013). We also quantified three hypervolatiles (methane (CH4), ethane (C2H6), and carbon monoxide (CO)) in C/2006 W3 (Christensen) whose perihelion distance is 3.1 AU (well outside the water-activated zone).

We continued our development of a taxonomy for comets based on volatile composition. We quantified production rates and related parameters for primary volatiles in comet C/2012 F6 Lemmon at infrared wavelengths (Paganini et al.). This paper presents the first study combining cometary spectra obtained with all three existing ground-based high-resolution infrared spectrographs (VLT/CRIRES, IRTF/CSHELL, and Keck/NIRSPEC), and was a collaborative effort between the Goddard and Univ. Hawai’i NAI Teams. See the reports by DiSanti et al. and Paganini et al.

We measured the unusual organic composition of comet 2P/Encke (Radeva et al. 2013), discovered two modes of water release in comet 103P/Hartley-2 (Bonev et al. 2013), and described in detail the chemical taxonomy of comets C/2012 F6 (Lemmon), (Paganini et al., in prep., DiSanti et al. 2013), C/2009 P1 (Garradd) (DiSanti et al., in prep.), and C/2001 Q4 and C/2002 T7 (Villanueva Report).

Co-I S. Milam and collaborators characterized the molecular content of Comet Lemmon using the Arizona Radio Observatory’s SubMillimeter Telescope, the JCMT, NRAO’s 100m GreenBank Telescope (GBT) and the Atacama Pathfinder Experiment (APEX) Telescope in Chile.

GCA members and collaborators led the first successful observations of an non-sidereal ephemeris source by the Atacama Large Millimeter Array (ALMA), and quantified aspects of the nuclear and extended release for several volatile species and dust in comet C/2012 F6 (Lemmon). The results provide the first clear evidence that HNC and H2CO are released in the coma (long suspected, and now confirmed), whereas HCN and CH3OH were released directly from the nucleus (Cordiner et al., in prep.).

Messengers from the Early Solar System – Meteorites

In an inter-disciplinary investigation, organic residue made in the Cosmic Ice Lab (Gerakines, Hudson) from benzene irradiated at 19 K by 0.8 MeV protons was then analyzed in the Astrobiology Analytical Lab (Callahan, Martin). Atmospheric pressure photoionization coupled to high resolution Orbitrap mass spectrometry was used to determine molecular composition, and accurate mass measurements suggested the presence of complex aromatic compounds. These results are consistent with the possibility that solid phase radiation chemistry of benzene produced some of the complex aromatics found in meteorites. Furthermore, radiation-induced reactions provide a facile mechanism for the extensive hydrogenation (likely) observed in meteoritic organics (Callahan et al. 2013).

In the Astrobiology Analytical Lab, Burton and collaborators analyzed six carbonaceous chondrites from the metal-rich CH and CB classes that had not previously been investigated for amino acids. They achieved the first reported discovery of amino acids in these meteorites, using enantiomeric and carbon isotopic measurements to support their extraterrestrial origin. They found distinct differences in their amino acid distributions, providing evidence that multiple mechanisms were active in forming amino acids in CH and CB chondrites (Burton et al. 2013).

As part of a large meteorite research consortium, Glavin and collaborators analysed three fragments of the Sutter’s Mill meteorite, a CM carbonaceous chondrite that fell in California in April 2012. Using optimized analytical techniques in the AAL, they examined the amino acid content and bulk carbon and nitrogen isotopic ratios for these samples. The low abundances of amino acids found in the Sutter’s Mill samples compared to other CM2 meteorites was consistent with other measurements of Sutter’s Mill indicating that the meteorite’s parent body had experienced significant heating, up to 300°C prior to entry.

Burton & Dworkin continued to explore crystallization structures of amino acids and the possible role of these structures in amplifying enantiomeric excesses of meteoritic amino acids. The crystal structures of two such compounds were published (Brewer et al 2013, Butcher et al. 2013).

Early Moon and Outer Planet Satellites

Co-I R. Walker and collaborators completed analysis of highly siderophile element (HSE) abundances and Os isotopes in seven Apollo 17 impact melt breccias. Their results suggest that the Serenitatis impactor originated in the inner portion of the present asteroid belt. The formation of this basin was likely not a process that delivered substantial water and/or organics to the lunar crust (Sharp et al. 2013, submitted).

Laboratory investigations by M. Loeffler and Co-I Hudson revealed an efficient reaction for converting SO₂ into SO₄— (sulfate ion) in low-temperature ices that contain peroxide (H2O2). Europa’s surface ices contain both strong oxidants (e.g., H₂O₂) and sulfates, suggesting that such reactions could supply a sulfurous nutrient to an icy extremophile if present (Loeffler and Hudson 2013).

Early Mars

G. L. Villanueva, PI M. J. Mumma, and collaborators published a comprehensive search for 12 trace gases on Mars, targeting six organic-, one hydroxy-, three nitrogenous-, and two chlorinated-compounds, based on ro-vibrational spectra in the 2.8-3.7 μm spectral region. This paper (Villanueva et al. 2013b) ranked among the top 20 of all papers in journals published by Elsevier in 2013.

Co-I J. Eigenbrode’s research focuses on understanding the formation and preservation of organic and isotopic sedimentary records of ancient Earth and Mars. A member of the MSL Curiosity instrument team, in 2013 Eigenbrode co-authored seven papers on results obtained at Gale Crater, and she is now writing a perspectives paper on Martian organic geochemistry.

In the Astrobiology Analytical Lab (AAL), Co-I D. Glavin and collaborators M. Martin and C. Freissinet performed laboratory pyrolysis gas chromatography mass spectrometry (P-GCMS) experiments on a variety of terrestrial Mars analog samples and synthetic standards to better understand the origin of the chlorinated hydrocarbons detected by the SAM instrument at the Rocknest aeolian drift in Gale Crater. They demonstrated that the carbon in the chlorinated hydrocarbons detected at Rocknest most likely originated from MTBSTFA, one of the wet chemistry reagents used in SAM . However, the chlorine was derived from martian oxychlorine compounds, such as calcium perchlorate.

In the AAL, M. Callahan and collaborators analyzed the amino acid and nucleobase content of the shergottite Roberts Massif (RBT) 04262 using liquid chromatography-mass spectrometry (LC-MS). Nucleobases were not detected in formic acid extracts; however, a suite of protein and non-protein amino acids was detected in hot-water extracts. The distribution of these amino acids matched those previously measured from thermally altered carbonaceous chondrites. While previous results strongly indicated that most if not all of the amino acids in Martian meteorites were the result of terrestrial contamination, RBT 04642 provided the first reasonable indication of extraterrestrial amino acids in a Martian meteorite (Callahan et al. 2013).

In the Cosmic Ice Lab, collaborator Gerakines and co-I Hudson continued their laboratory work on amino acids, focusing strongly on their rates and modes of destruction by radiation on planetary bodies, with a strong emphasis on Mars and its subsurface regions. In this period, they showed that amino acids have a greater rate of radiation resistance (survival) on Mars in higher temperature regions, particularly when diluted in H₂O-rich ices (Gerakines and Hudson 2013).

Advanced Instrument development

In collaboration with ongoing ASTID (Brinckerhoff et al.) and PIDDP (Getty et al.) projects in our lab, the GCA-supported effort has focused on the demonstration of a two-step laser MS (L2MS) protocol and its comparison with one-step, or prompt, LDMS. In L2MS, analytes are desorbed as neutrals using a ~3 micron wavelength IR laser, followed within microseconds by an ionization pulse from a 266 nm UV laser. The L2MS approach has the advantage of less organic fragmentation (with lower desorption intensities) and high selectivity for aromatic species, such as polycyclic aromatic hydrocarbons (PAHs), with the chosen ionization wavelength (Getty et al. 2012).

Induced molecular dissociation is the deliberate fragmentation of gas-phase molecules under conditions that allow focused structural analysis with tandem mass spectrometry (MS/MS). We have explored the application of both photo-induced dissociation (PID), which uses a pulsed laser to fragment the species of interest, and collision-induced dissociation (CID), in which a highly-localized collision gas is introduced into the instrument prior to mass analysis. While CID is extremely challenging to achieve effectively in a miniature mass spectrometer, given limited pumping capacity and potential for arcing, we have recently succeeded in demonstrating He-gas CID of a simple test compound – pyrene – on an existing 12 cm length reflectron TOF-MS with a valved, micron-scale orifice into a modified collision cell. With the collision cell active, the pattern of fragment ions formed matches that seen in the literature, which is encouraging given the potential for significant mass biases in post-cell analysis. The mass resolution is somewhat degraded in this mode due to the unoptimized ion optics of this preliminary test setup.

In collaboration with the Mars Science Laboratory’s Sample Analysis at Mars (SAM) investigation and with the Mars Organic Molecule Analyzer (MOMA) mass spectrometer project, under development at Goddard for the 2018 ExoMars rover, our team has initiated a series of Mars analog test campaigns, comparing laser TOF-MS, laser ion trap mass spectrometer (ITMS), used on MOMA (Brinckerhoff et al. 2013), and GCMS, used on SAM and MOMA. The MOMA ITMS uses Mars-ambient laser desorption, followed by ingestion of prompt ions through a capillary into the ion trap, using a fast aperture valve. In contrast, laser TOF-MS is a strictly high-vacuum technique. Each approach has its pros and cons, and its peculiar biases for organic and inorganic compound analyses with “unprepared” solid samples. GCA-supported analyses of Mars-analog sediment samples from Lake Hoare, Antarctica (Bishop et al., 2013) have enabled us to probe the variation of total and compound-specific organic limits of detection (LODs) in different mineral matrices, in particular where varying levels of oxidation produce different spectral interferences, including the production of cluster ions in LDMS of metal-bearing minerals and high-C/H ratio organics. These results are being folded into data reduction tools as well as instrument operational protocols (such as laser energy scanning) under development for the highly resource-limited MOMA experiment.

Undergraduate Research Associates in Astrobiology (URAA)

2013 featured the Tenth URAA offering (Undergraduate Research Associates in Astrobiology), a ten-week residential research program at the Goddard Center for Astrobiology (GCA) (http://astrobiology.gsfc.nasa.gov/education.html). Competition was very keen, with an oversubscription ratio of 3.0. Students applied from over 19 colleges and universities in the United States, and 6 Associates from 6 institutions were selected. Each Associate 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.

Education and Public Outreach (sample activities):

Individual GCA scientists were involved in a total of over 47 EPO events. These voluntary efforts included public lectures, video interviews, laboratory tours, and engagements with the broadcast media and social network designed to convey the excitement of their scientific discoveries. They reached a diversified audience of almost 900 people through individual events, and over 5 million people through video broadcasts.

Published papers

GCA members appeared as lead- , principal- , or co-author on 58 distinct scientific publications during this reporting period. Individual citations appear in the Bibliography at the end of this Report.