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Project Reports

• Modeling and Observation of Disks Project

  The broader goal of this NAI team is to understand and follow the evolution of complex, prebiotic organic molecules from the interstellar medium to their incorporation into planets. This Project’s work focuses on chemical evolution in the protoplanetary disk stage of planetary system formation. Disk matter provides the raw material for planet formation and its composition is thus expected to have a direct bearing on the composition of planets and eventually, the origin of life on them. We study disk chemical evolution via a two-pronged approach: (i) theoretical modeling of disk physical structure and its chemistry in time and the transport of matter in the disk as it evolves, and (ii) constructing synthetic line and continuum spectra and images of gas and dust in disks to compare with observational data from ground and space-based telescopes. New chemical networks that incorporate results from the Laboratory and Quantum Calculation Projects are developed and disk modeling results compared with observations to infer conditions under which the solar system and exoplanets formed.

  ROADMAP OBJECTIVES: 1.1 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 1.2 3.1 3.2 3.3 3.4

• Understanding Past Environments on Earth and Mars

  In this task we performed research to understand the evolution of habitable environments on Earth and Mars, both of which serve as potential analogs for habitable environments on extrasolar planets. We are expanding this line of work from past reports to span the entire histories of both planets. On Earth, we have sought to understand environments and time periods spanning the origins of life to the effects of human-generated greenhouse gas emissions on modern-day climate cycles. On Mars, we focus on the ancient conditions that could have allowed liquid water to be stable at the surface; on modern Mars, we focus on the debate on the presence, amount, and variability of methane in the Martian atmosphere.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 5.1 5.2 6.1

• Understanding Ancient Aqueous Environments on Mars

  Project 1: The goal of this project is to characterize ancient aqueous environments on Mars using Digital Terrain Model (DTM) analysis and mapping to understand the potential environments for past habitability. These include fluvial environments with morphological evidence for ponding, associated with hydrothermal systems and multiple episodes of surface and near surface flow in channelized systems. We will determine sediment and eroded volumes of fluvial landforms from DTM analysis and use transport equations and terrestrial analogs to understand likely discharges and flow durations.

  ROADMAP OBJECTIVES: 1.1 2.1 7.1

• Circumstellar Debris and Planetesimals in Exoplanetary Systems

  GCA astronomer Marc Kuchner studies the dynamics of debris disks, extrasolar analogs to the Kuiper Belt and the asteroid belt in our solar system, using NASA’s supercomputers. He develops numerical models of the orbits and the interactions of the planetesimals in these disks for use in interpreting images of them made with the Hubble Telescope and other NASA observatories. Together, the images and models teach us about how planetary systems form and evolve – the context within which processes affecting our Solar System are evaluated and extended to exo-planetary systems. An important goal is to extend these studies to a wider range of proto-planetary systems, thereby expanding the range of diversity within which the Solar System must be interpreted. Kuchner’s second initiative targets that objective.

  Accordingly, Kuchner invited the public to help him discover new planetary systems through a new website, launched in 2014. 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. Among these objects, thousands of planetary systems await discovery – recognizable by the dusty disks that surround them. But galaxies, interstellar dust clouds and asteroids also glow in the infrared, which stymies automated efforts to identify these disks. At Disk Detective.org, the volunteers find the disks by watching 10-second videos of objects seen by WISE, then classifying them by clicking on a selection of buttons on their screens.

  ROADMAP OBJECTIVES: 1.1 1.2

• Astronomical Biosignatures, False Positives for Life, and Implications for Future Space Telescopes

  In this task, we identify novel biosignatures and also identify “false positives” for life, which are ways for non-biological processes to mimic proposed biosignatures. Of primary concern are false positives that could mimic easier to detect biosignatures like O₂, which we plan to search for with future space-based telescopes. This is a growing area of research that VPL’s past work has motivated, leading to multiple research teams across the planet following our example. Our work continues to be at the forefront of this area of work, as we have identified new non-biological mechanisms for mimicking signs of life. Further, we explained the ways in which these non-biological mechanisms could be identified, and “true positives” from biology confirmed with secondary measurements. Finally, we communicated these lessons to various teams that are studying concepts for future missions that would search for these signs of life. This connection to missions will ensure that our research is incorporated into those missions, so that they will not be “tricked” by these false positives.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.3 5.2 5.3 7.2

• Inv 3 – Planetary Disequilibria: Characterizing Ocean Worlds and Implications for Habitability

  INV 3 looks at how, where, and for how long might
disequilibria exist in icy worlds, and what that may imply in terms of
habitability. A major interest for this work is how ocean composition affects habitability. We are investigating chemistry behaves under conditions of pressure, temperature, and composition not found on Earth. Our simulations of deep ocean world chemistry couple with models for ocean dynamics, ocean ice interaction, and tectonics within the ice. We are examining each of these, how they interact, and how they relate to what future missions may discover. Members of our team are involved in missions to Mars, Jupiter’s moon Europa, Saturn, and Pluto. We are also involved in studies of exoplanets, and are working to understand how ocean worlds like Ganymede and Europa might provide analogues for more distant watery super-earths.

  ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 4.2 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 and continuing use of the Hubble Space Telescope, we are poised to break open the study of young exo-planetesimals, 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 7.2

• Inv 4 – Observable Chemical Signatures on Icy Worlds: A Window Into Habitability of Subsurface Oceans

  INV 4 aims to answer the Key Question: What can observable surface chemical signatures tell us about the habitability of subsurface oceans? We will shed light on the evolution of ocean materials expressed on the surface of airless icy bodies and exposed to relevant surface temperatures, vacuum, photolysis and radiolysis. To this end, we have initiated an experimental program designed to establish the extent to which chemical compositions of icy world surfaces are indicative of subsurface ocean chemistry. Our initial experiments have focused on freezing solutions of sodium, magnesium, sulfate and chloride – four commonly suggested major components of Europa’s Ocean.

  ROADMAP OBJECTIVES: 1.1 2.2 7.1

• Exoplanet Detection and Characterization: Observations, Techniques and Retrieval

  In this task, VPL team members use observations and theory to better understand how to detect and characterize extrasolar planets. Techniques to improve the detection of extrasolar planets, and in particular smaller, potentially Earth-like planets are developed, along with techniques to probe the physical and chemical properties of exoplanet atmospheres. These latter techniques require analysis of spectra to best understand how it might be possible to identify whether an extrasolar planet is able to support life, or already has life on it.

  ROADMAP OBJECTIVES: 1.1 2.2 7.2

• Exploring the Evolution of the Water and Organic Reservoirs in the Solar System

  This project investigates the evolution and stability of water and organic reservoirs in our Solar System, with particular emphasis on the characterization of the current and ancient habitability of planet Mars. We employ extremely powerful observatories (e.g., ALMA, Keck, VLT, future JWST) to acquire high spatial and spectral resolution maps of the isotopic and organic signatures on several bodies in the Solar System. These maps allow us to investigate the stability and evolution of their atmospheres, while localized plumes can be used to identify regions of active release. In this reporting period, we emphasized three areas:

  1. We advanced our pioneering work on characterizing the evolution of water on Mars, by developing a new observational plan that combines the power of ALMA, of Keck and of MAVEN to obtain maps of the water D/H signatures on Mars.

  2. We identified previously unknown chemical processes affecting singlet-O₂ and odd-oxygen on Mars, which may be indicative of a much more active photochemical cycle (with the possible intervention of heterogeneous processes).

  3. We provided science leadership in the investigation of Mars with the James Webb Space Telescope (JWST), and established a variety of observing modes and scientific opportunities.

  ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 4.1 7.1

• 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 spanned climate modeling to atmospheric escape. We showed that multiple stable states of climate could exist for water-rich worlds, including both habitable and uninhabitable states, suggesting that water-rich planets in the habitable zone are not necessarily habitable. Atmospheric escape models were 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. We also showed that pre-main sequence evolution could lead to strong atmospheric escape of water on otherwise habitable worlds, potentially rendering them uninhabitable. We defined the first metric to rank an exoplanet’s potential to support surface liquid water based on fundamental data from transit observations. 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 3.4

• Planetary Surface and Interior Models and SuperEarths

  We use computational and theoretical 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 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

• Exploring the Structure and Composition of Exoplanets With Current and Future Telescopes

  This project addresses a major frontier of planetary science and astrobiology, namely the identification and characterization of habitable (and inhabited) exoplanets. 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. Targeted questions include the possibility of bulk compositional variations among planets, and the presence or absence of a stratospheric temperature inversion on individual planets. In this reporting period, we emphasized four areas:
  1. We improved our modeling and analysis of exoplanet transit and eclipse measurements obtained with the Hubble Space Telescope (HST) and the Spitzer Space Telescope on highly irradiated, Jupiter-mass planets.
  2. We improved our data analysis methods to better understand aspects of measuring the chemical composition of the planet’s atmosphere, and we advanced the chemical and thermal modeling of the planet’s hot dayside.
  3. We developed simulations of future observations with the James Webb Space Telescope (JWST), and we provided science leadership for a future balloon-borne telescope that can perform transit spectroscopy of hot exoplanet atmospheres.
  4. We estimated the discovery yield of future Earth-like exoplanet imaging missions as part of the planning process for the next Astrophysics Decadal Survey, and we are now expanding this effort to estimate the science yield from spectroscopic characterization of them.

  ROADMAP OBJECTIVES: 1.1 1.2 7.2

• Project 7: Mining Archaeal Genomes for Signatures of Early Life: Comparison of Metabolic Genes in Methanogens

  Methanogens represent the largest diversity among the archaea and have the unique ability to generate methane from simple compounds such as carbon dioxide, acetate and methylamines which were common in the anaerobic environments of early Earth and perhaps Mars. Methane biosynthesis also requires the presence/uptake of important ions such as sulfates, sulfides, carbonates, phosphates, and various light metal ions. In this project, we are attempting to analyze the evolution of the methanogens’ central cellular functions of translation, transcription, replication, and metabolism. To accomplish this, we are constructing the metabolic and regulatory networks of Methanosarcina acetivorans, the most complex methanogen known, and using these models to establish a framework for studying the evolution of methanogens. Results will be tested through microfluidic studies using varying carbon and ion sources.

  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

• Interstellar and Nebular Chemistry: Theory and Observations

  We continue to undertake theoretical and observational studies pertaining to the origin and evolution of organics in Planetary Systems, including the Solar System. In this performance period, we have focused on studies aimed at understanding the origin and processing of organics in the earliest evolutionary phases of stars like the Sun. These include formation pathways and related isotopic fractionation effects.

  We have continued observational programs designed to explore the chemical composition of comets and establishing their potential for delivering prebiotic organic materials and water to the young Earth and other planets. State-of-the-art international facilities are being employed to conduct multi-wavelength simultaneous studies of comets in order to gain more accurate abundances, distributions, temperatures, and other physical parameters of various cometary species. We are also leading an international collaboration to study the organic composition of Titan with the Atacama Large Millimeter Array (ALMA).

  ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 3.2 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 amount of energy available for the climate and to 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

• Modeling and Observations of Exoplanets

  The focus of this project is to use the Doppler velocity technique to detect and characterize extrasolar planets and use exoplanet data to establish the nature and diversity of planetary systems in the galaxy, with an emphasis on establishing the abundance of habitable planets in the universe.

  ROADMAP OBJECTIVES: 1.1 1.2

• NNX15AT33A Origin and Evolution of Organics and Water in Planetary Systems

  Research by the Blake group (CalTech) supported by the NAI has centered on a joint laboratory and observational program, designed with the participation of Goddard node scientists, that aims to investigate the chemistry of water and simple organics in the protoplanetary disk analogs of the early solar nebula, in comets, and in the atmospheres of extrasolar planets. The laboratory work has involved the creation of novel high bandwidth instruments from the microwave to the THz regime that can probe both gaseous and condensed phase (liquid and solid) materials. Particular emphasis has been placed on the study of small chiral (that is, ‘handed’) organic species, with a view toward establishing whether the homochirality exhibited on the Earth is stochastically or deterministically derived. We combine the laboratory studies with astronomical observations at radio (VLA, GBT, ALMA), far-infrared (SOFIA, Herschel archival data), and infrared (Keck/VLT, Spitzer archival data) wavelengths. A recent highlight is the first detection of a chiral species toward the Galactic Center, as is described in this report

  ROADMAP OBJECTIVES: 1.1 1.2 3.1

• Environmental and Biological Signatures in Yellowstone National Park Silica Precipitating Hot Springs

  Radiation from the Sun potentially affects solids, liquids, and gases found on the surfaces of planets. Radiation exposure could change the chemical and mineralogical make-up of the surface materials. Sample-return missions aim to collect samples, cache them for a period of time, and then return them to Earth for additional analysis. We have performed field experiments to document environmental radiation levels and exposures and their impact on recently formed materials and associated organic matter.

  ROADMAP OBJECTIVES: 1.1 2.1 6.1 7.1 7.2

• The MER Mission to Mars

  NAI team member Andrew Knoll continued to work as part of the science team for the MER mission to Mars. Exploration continues along the clay-rich lip of Endeavor crater. Publications in 2015 include a synthesis of recent research in the Endeavour region and a analysis of Mn-bearing surface features exposed along Murray Ridge.

  ROADMAP OBJECTIVES: 1.1 2.1

• Rock Sample Biosignature Library and Automated Identification of Biosignatures

  The goals of this project are to: 1) build a Raman spectra and imaging library of rock samples containing biosignatures as no publically available online sample library currently exists; and to: 2) use this library as testing and training sets to develop automated classifiers for identifying biosignatures in rock spectra. Building a sample library and developing automated classifiers would enable field scientists or robotic explorers on the surface of Mars or elsewhere to automatically identify biosignatures in rock samples from Raman spectra out in the field.

  ROADMAP OBJECTIVES: 1.1 2.1 7.1

• Surface Mediated Reactions in the Primitive Solar Nebula

  Hydrogen, carbon monoxide and nitrogen gases are abundant in the primitive solar nebula, as are silicate dust and metallic grains. These gases can react on such grain surfaces to produce an abundance of carbon-bearing products that include volatile hydrocarbons, amines, alcohols, aldehydes and acids as well as more complex, less volatile species such as carbon nanotubes. Refractory carbonaceous deposits catalyze additional surface reactions. Nebular environments span a large range in time, temperature, pressure, catalyst composition and secondary reactions. We are working to understand the rates and products of such reactions that could occur in nebular environments.

  ROADMAP OBJECTIVES: 1.1 3.1

• Undergraduate Research Associates in Astrobiology (URAA)

  2015 saw the twelfth session of our summer program for talented science students (Under-graduate 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 again very keen, with an over-subscription ratio of 4.7. Students applied from over 19 Colleges and Universities in the United States, and 4 Interns from 4 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 1.2 2.1 2.2 3.1 6.2 7.1

• Project 3E: Genesis of High-δ18O Archean Chert, Pilbara Craton, Australia

  The cherts of the Strelley Pool formation host the oldest generally accepted evidence of life, stromatolites, organic matter and microfossils. Oxygen isotope ratios provide independent evidence to evaluate conditions when quartz formed. These results support habitable conditions during formation of early quartz and late alteration for genesis of late high δ¹⁸O-quartz.

  ROADMAP OBJECTIVES: 1.1 4.1 7.1

• Project 3F: 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), the Superior craton (Canada). While intriguing microstructures have been observed, thus far no confirmed shock microstructures have been encountered in our Archean sample suites. 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. We are currently in the process of more in-depth surveying (e.g., >1000 grains/sample) to test for very low frequency occurrency events. Our detailed search continues…

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• Project 4B: New Standards for Analysis of O and C Isotope Ratios in Ca-Mg-Fe Carbonates

  Stable isotope ratios are a powerful tool for determining the temperature and fluid conditions during formation of carbonates that host evidence for early life on Earth. However, sedimentary carbonates are often zoned at μm-scale and conventional analysis yields average values. We developed a suite of standards for the dolomite-ankerite series that allow us to make the first accurate SIMS (Secondary ion mass spectrometry) analyses oxygen and carbon isotope ratios at 1-10 μm-scale for these important carbonate minerals.

  ROADMAP OBJECTIVES: 1.1 4.1 4.3 7.1