https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/The NASA Postdoctoral Program has been extraordinarily successful in supporting new leaders in the astrobiology community. Upon completion of their postdoctoral fellowships, the Astrobiology Fellows are given the opportunity to present a seminar to share their work with one another and with the astrobiology community at large. Seminarsen-usSat, 06 Jun 2020 05:18:38 +0000https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/6/6/investigating-habitable-environments-on-mars-using-orbital-and-rover-based-imaging-spectroscopy/The Mars Science Laboratory Curiosity rover is currently exploring an ancient habitable environment at the base of Mt. Sharp in Gale crater. The diverse stratigraphic sections along Curiosity’s future traverse record multiple environmental transitions that can provide insights into global-scale processes and the evolution of early aqueous environments on Mars. To better interpret these complex mineral stratigraphies, it is critical to correlate the mineralogic transitions with morphology, texture, slope, and other aspects of the physical stratigraphy; such correlations can be made between orbital and rover-based imaging spectroscopy measurements. Quantitative visible to near-infrared (VNIR) data from Curiosity’s Mastcam instrument allows for broad distinctions between different iron mineralogies, oxidation states, and hydrated phases. Mastcam multispectral images can be used to map spectral diversity across a given outcrop in combination with textural information such as grain size, sedimentary structures, diagenetic features, and contact geometries. At distances of up to several kilometers, Mastcam observations can be correlated with the larger-scale stratigraphy, and used to enhance mineralogical and stratigraphic mapping made from orbit, such as from the Mars Reconnaissance Orbiter (MRO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and High Resolution Imaging Science Experiment (HiRISE) instruments. Here I will present an overview of the instrumentation, technique, and major results from Mastcam’s imaging spectroscopy investigation at Mt. Sharp, and correlations with HiRISE and CRISM data to interpret the aqueous alteration history. I will also discuss plans for imaging science with the Mastcam-Z instrument on NASA’s next rover, which will launch in 2020. BIO: Dr. Melissa Rice is an Assistant Professor of Planetary Science at Western Washington University, where she has held a joint appointment in the Geology Department and the Physics & Astronomy Department since 2014. She received her Ph.D. from the Department of Astronomy at Cornell University in 2012, and was a NASA Astrobiology Institute Postdoctoral fellow at Caltech from 2012-2014. Her research focuses on the sedimentology, stratigraphy and mineralogy of Mars. She is a collaborator on the active Mars Exploration Rover Opportunity missions, a Participating Scientist on the Mars Science Laboratory rover mission, and a Co-Investigator for the Mastcam-Z investigation in development for the Mars2020 rover mission.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/6/6/investigating-habitable-environments-on-mars-using-orbital-and-rover-based-imaging-spectroscopy/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/6/1/chemical-gardens-chimneys-and-fuel-cells-simulating-prebiotic-chemistry-in-hydrothermal-vents-on-ocean-worlds/Planetary water-rock interfaces generate energy in the form of redox, pH, and thermal gradients, particularly in hydrothermal systems where the reducing, heated vent fluid feeds back into the more oxidizing ocean. Alkaline vents produced by serpentinization have been proposed as a possible location for the emergence of life on the early Earth due to various factors, including the mineral precipitates that resemble inorganic catalysts in enzymes and the presence of electron donors and acceptors in hydrothermal systems (e.g. H2 + CH4 and CO2) that may have been utilized in the earliest metabolisms. Many of the factors prompting interest in alkaline hydrothermal vents on Earth may also have been present on early Mars, or even presently within icy worlds such as Europa or Enceladus. Of particular importance for possible proto-metabolic reactions in alkaline hydrothermal systems are mineral chimneys that precipitate at the vent fluid / seawater interface. Hydrothermal chimneys are an example of geological chemical gardens – a self-organizing non-equilibrium process that forms complex structures fueled by steep concentration gradients across the reaction-precipitation zone. Chemical garden and inorganic membrane systems have many properties of interest to the origin of life that can be simulated in the laboratory, for example: they can precipitate metastable catalytic mineral phases; the chemical garden structure can act as a flow-through chemical reactor and concentrator; and they can even generate electrical energy from the trans-membrane gradients and drive redox reactions. In this talk I will give an overview of how we use chemical gardens to simulate far-from-equilibrium geochemical systems such as vents, and future directions for using electrochemical / fuel cell techniques to characterize prebiotic potential and habitability in seafloor systems.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/6/1/chemical-gardens-chimneys-and-fuel-cells-simulating-prebiotic-chemistry-in-hydrothermal-vents-on-ocean-worlds/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/3/7/the-synthesis-of-an-artificial-genetic-polymer-from-small-molecules-to-proto-nucleic-acids/We are seeking to understand how the origin of the cellular machinery that constitutes life is founded on the chemical interactions that give rise to replicative and evolutionary characteristics. For example, the aqueous medium of a cell enables Watson-Crick base-pairings between complimentary DNA strands, but does not allow for condensation reactions between nucleobases and carbohydrates in which the DNA strands are composed. As a consequence, we are seeking to broaden our perspective on how informational elements are formed from the prebiotic inventory. Pyrazine nucleic acid (PzNA) which has a backbone structurally similar to glycerol nucleic acid (GNA), has been proposed to exhibit base-pairing properties similar to adenine and uracil and to be derivable from pentoses. This polymer is an origin of life inspired design that reconciles both prebiotic and classical organic chemistry towards determining the type of proto-informational polymers that may have emerged under plausible primitive conditions. With an aim to study PzNA, we have explored potential prebiotic routes to the pyrazine-2-one propanediol and 2-aminopyrazine propanediol starting from the aldosugars, and have also developed a synthetic route to pyrazine-2-one propanediol phosphoramidite suitable for automated PzNA oligomer synthesis. En route, we discovered an “apparent” regioselective protection of pyrazine-2-one derivatives in the presence of a secondary hydroxyl group that proved crucial in the preparation of the pyrazine-2-one phosphoramidite. The regioselectivity observed is proposed to be of general interest in the context of heterocyclic chemistry. In the larger context of origin of life studies, it points to the importance of keto-enol preferences of the canonical nucleobases versus pyrazine heterocycles in functioning as recognition elements. This chemistry becomes more apparent at the level of oligonucleotides. While the simple architecture and prebiotic relevance indicates a promising primordial replicator, base-pairing results of the oligonucleotides prepared in this study points to an informational polymer weakened by the facile keto-enol tautomerization of the pyrazine heterocycles. We hope that such discoveries will bring us closer to understanding the nature of living systems through organic chemistry.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/3/7/the-synthesis-of-an-artificial-genetic-polymer-from-small-molecules-to-proto-nucleic-acids/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/2/8/quantifying-constraints-on-metabolic-diversity-patterns/A shared goal of astrobiology, ecology, and evolutionary biology is understanding the general principles governing spatiotemporal patterns in biological diversity. Exergonic metabolic diversity is the diversity of energy-yielding reactions harnessed by a living system. Because energetics shape the distribution and functioning of life, exergonic metabolic diversity is a fundamental dimension of biodiversity that is particularly relevant to astrobiology and biogeochemistry, as well as to understanding the macroecology and macroevolution of microbes. In this seminar, I will present theory and data quantifying how chemical thermodynamics constrain patterns in the richness and turnover rate of the composition of exergonic metabolic reactions of organisms and ecosystems along environmental gradients such as pH, temperature, and oxygen. I will also provide a synthesis of the other factors, in addition to thermodynamics, that constrain exergonic metabolic diversity patterns, including chemical kinetics, biological scaling, and ecological and evolutionary dynamics. The developed theory elucidates the degree to which various physicochemical variables can influence exergonic metabolic diversity, with implications for the functioning of biogeochemical systems and patterns of functional, taxonomic and phylogenetic diversity in microbes.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2016/2/8/quantifying-constraints-on-metabolic-diversity-patterns/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/12/7/the-ecological-physiology-of-earths-second-oxygen-revolution/Living animals display a variety of morphological, physiological and biochemical characters that enable them to live in low oxygen environments. These features and the organisms that have evolved them are distributed in a regular pattern across O2 gradients associated with modern oxygen minimum zones, providing a template for interpreting the stratigraphic covariance between inferred Ediacaran-Cambrian oxygenation and early animal diversification. Although Cambrian oxygen must have reached 10-20% of modern levels, sufficient to support the animal diversity recorded by fossils, it may not have been much higher than this, approaching today’s level only later in the Paleozoic Era. Nonetheless, Ediacaran-Cambrian oxygenation may have pushed surface environments across the low, but critical, physiological thresholds required for large active animals, especially carnivores. Continued focus on the quantification of Proterozoic pO2 will provide the definitive tests of oxygen-based co-evolutionary hypotheses.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/12/7/the-ecological-physiology-of-earths-second-oxygen-revolution/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/11/2/organic-astrochemistry-amino-acids-and-amines-in-meteorites/Carbonaceous chondrites represent some the oldest and most primitive pieces of material formed in the Solar System; indeed, they could even be older than the Sun itself. These carbon-rich meteorites may have delivered an important concentration of organic compounds and water to the primitive Earth. Multiple organic classes, including those required for life (e.g. amino acids, carboxylic acids and nucleobases) have been identified from carbonaceous chondrites, providing valuable insights into the chemical inventory of the early Solar System, the primordial synthesis of organic matter, and the question of how life appeared on Earth. Amino acids constitute the basic building blocks of all protein-based living organisms on Earth and thus, they are among the most intriguing and studied meteoritic organic compounds. Homochirality (predominance of the L-enantiomer) in terrestrial biological proteins is a fundamental feature of life as we know it. L-enantiomeric excesses have been observed in some meteoritic amino acids, raising important questions about a potential link between meteorites and terrestrial homochirality. In addition, the stable isotopic compositions (D, 13C, 15N) of meteoritic organic compounds provide information on their formation mechanisms and histories. Contrasting the distribution, chirality and isotopic composition of meteoritic organic compounds in a wide range of carbonaceous chondrites provide important insights on the composition and environments of the protosolar nebula, the meteorite parent bodies, and may well provide clues about their synthesis and survival during the formation of our Solar System. We will present results from our extensive investigation on the abundance and molecular distribution of amino acids, and amines extracted from meteorites. We will discuss their potential prebiotic origins and relevance to the emergence of life on Earth.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/11/2/organic-astrochemistry-amino-acids-and-amines-in-meteorites/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/4/6/quantifying-constraints-on-metabolic-diversity-patterns/_This talk has been postponed and will rescheduled for a later date. Thank you for your patience!_ A shared goal of astrobiology, ecology, and evolutionary biology is understanding the general principles governing spatiotemporal patterns in biological diversity. Exergonic metabolic diversity is the diversity of energy-yielding reactions harnessed by a living system. Because energetics shape the distribution and functioning of life, exergonic metabolic diversity is a fundamental dimension of biodiversity that is particularly relevant to astrobiology and biogeochemistry, as well as to understanding the macroecology and macroevolution of microbes. In this seminar, I will present theory and data quantifying how chemical thermodynamics constrain patterns in the richness and turnover rate of the composition of exergonic metabolic reactions of organisms and ecosystems along environmental gradients such as pH, temperature, and oxygen. I will also provide a synthesis of the other factors, in addition to thermodynamics, that constrain exergonic metabolic diversity patterns, including chemical kinetics, biological scaling, and ecological and evolutionary dynamics. The developed theory elucidates the degree to which various physicochemical variables can influence exergonic metabolic diversity, with implications for the functioning of biogeochemical systems and patterns of functional, taxonomic and phylogenetic diversity in microbes.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/4/6/quantifying-constraints-on-metabolic-diversity-patterns/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/3/2/polarimetry-of-exoplanetary-atmospheres-haze-molecules-and-biosignatures/Detecting and characterizing exoplanetary atmospheres is an important step towards finding life on other planets. The light scattered in the planetary atmosphere is linearly polarized, and in general, when the planet revolves around the parent star, the scattering angle changes and linear polarization vary. The observed polarization variability exhibits therefore the orbital period of the planet and reveals the inclination, eccentricity, and orientation of the orbit. Due to their proximity to the star, hot giant planets with short orbital periods (Hot Jupiters) may develop peculiar atmospheres and halos which effectively scatter the light in the blue spectral region. This can give rise to a degree of polarization detectable with the currently existing modern polarimeters. Parameters of this polarization, e.g., wavelength dependence, are defined by physical conditions in upper layers of the planetary atmoshpere. Recently, we have demonstrated that polarized reflected light can be detected from exoplanetary atmospheres (Berdyugina et al. 2008, 2011). We have determined for the first time the geometrical albedo in different colors and concluded that the high reflectivity ofthe hot Jupiter HD189733b in the blue due to Rayleigh scattering determines its blue appearance. This was confirmed with secondary eclipse spectro-photometry in the near UV (Evans et al. 2013). We continue our polarimetric survey using telescopes on the Canary Islands and Hawaii and routinely achieve polarimetric accuracy of 10^(-5). New observations and results will be presented in this talk. We have also started a study of signatures of biological polarization, e.g., selective light absorption or scattering by biogenic molecules (Berdyugina et al. 2015). We have carried out a laboratory spectro-polarimetric study of light reflected by various bacterial types and terrestrial plants, which contained different photosynthetic and non-photosynthetic pigments. Measurements on non-biological samples (e.g., rocks and sands) were also performed in order to avoid false positives. These measured reflection spectra were then used to synthesize polarized spectra of Earth-like planets with various contributions from the land, photosynthetic organisms, ocean, atmosphere, and clouds. We estimate the required photometric and polarimetric sensitivity to detect such planets in habitable zones of nearby stars. We show that spectro-polarimetry provides a great advantage for high-contrast remote detection of biological photosynthetic organisms as compared to spectroscopy.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/3/2/polarimetry-of-exoplanetary-atmospheres-haze-molecules-and-biosignatures/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/2/9/collaborative-practices-in-astrobiology-research-the-nasa-astrobiology-institute/The NASA Astrobiology Institute is a cross-disciplinary research network established to study astrobiology related questions, with over 700 active researchers, affiliated with approximately 130 institutions. The broadness of the topic (life in the universe) and the distributed nature of the network require a collaborative research agenda from an interdisciplinary perspective. This presentation assesses interdisciplinary collaborative practices at NAI for the CAN 4 and CAN 5 teams (14 in total), by focusing on four areas: (i) communication behaviors [use of virtual collaboration tools and assessment of online meetings]; (ii) data and information behaviors [attitudes towards and practices of research data management]; (iii) collaborative work and interdisciplinary interaction [metrics for interdisciplinary and collaborative work and qualitative analysis of interdisciplinary work]; and (iv) institutional identity [what does it mean to be an astrobiologist, and the researchers' relationship with the NAI as an organization]. The findings and recommendations provided in this presentation are useful to improve efficient communication, data sharing, collaborative analysis and problem solving; to foster interdisciplinary science and collaborative work; and to strengthen institutional identity.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2015/2/9/collaborative-practices-in-astrobiology-research-the-nasa-astrobiology-institute/https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2014/11/3/ancient-reconstructions-and-recombinations-the-complex-evolutionary-histories-within-single-genes/Much recent work in phylogenetic inference has focused on using large numbers of genes to elucidate the complex histories of entire genomes, through automated pipelines using increasingly sophisticated evolutionary models. However, close inspection of sites within single genes can still reveal critical new information for studying the evolution of early life. Ancestral reconstructions of the pre-LUCA paralog ancestors of aminoacyl-tRNA synthetase (aaRS) proteins reveal how the early genetic code co-evolved with the protein synthesis machinery. Identification of conserved ancestral sites within deeply branching “rare” types of some aaRS proteins reveal the existence of extinct relatives of LUCA, and the important role of horizontal gene transfer (HGT) even at this very early time. Finally, clusters of conserved sites within many protein families, including aaRS, ribosomal proteins, and elongation factor proteins, support conflicting sets of bipartitions within gene trees. These sites reveal complex histories of partial HGT and within-gene recombinations that both obscure and reveal the true deep relationships and patterns of HGT between organismal lineages, including eukaryotes.https://nai.nasa.gov/seminars/early-career-seminars/npp-alumni-seminars/2014/11/3/ancient-reconstructions-and-recombinations-the-complex-evolutionary-histories-within-single-genes/