Seminar Archive

Missed the last seminar series?
See below for a list of past UWAB seminars, including video recordings (when available).
 
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2014

 
04/08/2014
 
Tom Tobin (University of Washington)

Modeling The Climate Effects of Deccan Traps Flood Volcanism (UWAB Research Rotation Presentation)

 
This presentation will relate work done towards an Astrobiology research rotation completed with Dr. Cecilia Bitz. The goal of this project was model the potential climatic effects from Deccan Traps Flood Volcanism. The Deccan Traps may have been a contributing factor the end Cretaceous mass extinction, but it disputed whether they are sufficiently large enough to have clear climate effects. Warming events have been temporally associated with the timing of Deccan. Our relatively simple models suggest that the Deccan Traps could feasibly have created the observed warming patterns, but much hinges on the range of different published estimates for Deccan Traps gas emissions.
 
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Amit Misra (University of Washington)

Measuring Interdisciplinarity Using Citations (UWAB Research Rotation Presentation)

 
Interdisciplinarity is an integral part of modern research, especially in astrobiology, but it can often be difficult to measure interdisciplinarity. We've developed a citation-based metric for measuring interdisciplinarity that uses the Jensen-Shannon divergence to compare how similar a journal's citation pattern is to journals it cites and is cited by. I'll describe the advantages of this method over existing methods and the limitations of the metric. I will discuss notable results, such as the low interdisciplinarity of Astronomy journals, and where journals of interest to Astrobiologists fall in the rankings.
 
(Recording Unavailable)
 
 
04/15/2013
 
Jonathan Fortney (UC Santa Cruz)

Characterizing A New Kind of Exoplanet: Low-Mass Low-Density Exoplanets

 
NASA's Kepler Mission has revealed that the most common size of planet in our galaxy may be those from 2-3 Earth radii. Such medium-sized planets are significantly more common on close-in orbits than Neptune and Jupiter-class giant planets. We have no analog for these planets in our solar system. To explain their size, most require a thin envelope of H/He gas, atop a core of high pressure rock and/or water. An example relatively close to home is planet GJ 1214b, which is 2.6 Earth radii and 6 Earth masses, and orbits a cool red dwarf star near the Sun. This planet has been extensively studied with the Hubble and Spitzer Space Telescopes. In this talk, Prof. Fortney will first discuss our current understanding of the composition and atmospheric physics of GJ 1214b, which is potentially a prototype for this class of low-mass low-density planets, and will describe the physical processes that may be common to this type of fascinating planets.
 
 
 
04/22/2014
 
Leslie Rogers (California Institute of Technology)

Bulk Composition and Habitability of Sub-Neptune-Size Exoplanets

 
Sub-Neptune and super-Earth sized planets are a new planet category. They account for 80% of the planet candidates discovered by Kepler, and 0% of the planets in the Solar System. What is the nature of these sub-Neptune-size planets, how did they form, why are they so numerous, and could they support liquid water oceans? Dr. Rogers will review some highlights from the complement of exotic sub-Neptune-size planets discovered to date and present an updated planet mass-radius diagram. With planet interior structure models, she will constrain the masses and radii both of rocky planets and of volatile-rich planets harboring liquid water oceans. These insights into the size demographics of rocky and volatile-rich planets have important implications for the occurrence rate of habitable planets throughout the galaxy.
 
 
 
04/29/2014
 
Fang-Zhen Teng (University of Washington)

The Origins of the Moon, Rise of Atmospheric Oxygen, Volcanic Eruption, and Continental Weathering: A Non-Traditional Isotope Perspective

 
Recent developments in non-traditional isotope geochemistry have significantly advanced our understanding of the origin of the solar system, the formation and differentiation of the solid Earth, and the evolution of the atmosphere and biosphere. This talk will focus on how non-traditional isotopes can be used to constrain the giant impact theory on formation of the Moon, the rise of atmospheric oxygen, magma eruption rates and the change of continental composition by weathering.  
 
(Recording Unavailable)
 
 
05/06/2014
 
Leslie Bebout (NASA Ames Research Center)

Microbial Systems: Nexus roles for Astrobiology, Energy and Space

 
Life on Earth is dominated by microbes, in terms of biomass, overall rates of activity, use of potentially available habitats, and length of time on the planet. Much of our search for early life on Earth focuses on microbial mats and stromatolites, in which a diverse set of photosynthetic and non-photosynthetic microbes live in complex, interdependent assemblages. The nature of these systems can vary dramatically depending on the specific environment. This talk will present a glimpse at the diversity of assemblage types from different locations including Bahamian (marine -carbonate), temperate intertidal siliciclastic, and hypersaline environments, and illustrate some of the new findings from an ongoing in depth survey of a local system on the Monterey Bay, Ca. Due to the different mineral and biological content, these different types of benthic systems may process irradiance differently, which is both an old and new topic of interest for our working group and of increasing interest for the remote sensing community. Since microbial ecosystems are also the loci where the myriad processes necessary for regenerative cycling of energy and elements occur on Earth (and support higher life forms, including our own), increasingly these microbial systems are being explored and applied to address current day challenges in sustainability of renewable energy sources. These capabilities also make microbial ecosystem management a logical component of future space exploration research and technologies. The current Microbial Observatory initiative for ISS, is one such example, and a brief overview of current efforts to engage the scientific community on ecological and related human health considerations topic will be presented.
 
 
 
05/13/2014
 
Michael Line (UC Santa Cruz)

Remote Sensing of Extrasolar Planets

 
Thanks to the Kepler spacecraft, we now know that nearly every star in our galaxy possesses a planet. Understanding these planets is key to understanding our place in the universe. Over the past decade we have begun to characterize exoplanet atmospheres using ground and space based observatories. Such observations reveal clues to the composition and temperature structures of these planets. Dr. Line will discuss how we can use statistical methods combined with radiative transfer, known as atmospheric retrieval, to infer the temperatures and compositions of these planets, and will describe what we have learned about a small handful of extra solar planet atmospheres from these methods. Understanding the composition of these objects offer clues to the atmospheric chemistry, dynamics, their formation history. Time permitting, Dr. Line will address how we might apply these tools to earth-like transmission spectra and what we might be able to say about their atmospheres.
 
 
 
05/20/2014
 
John Priscu (Montana State University)

Microbial Habitability of Icy Worlds

 
As active exploration of space begins its sixth decade, we have, for the first time in the history of humanity, the tools and techniques to probe the profound questions of planetary habitability: how has life evolved and survived on Earth for more than 3.5 billion years?; is there life beyond Earth? These questions served as a driving force for the space program and, eventually led to the interdisciplinary field of astrobiology in the late-1990s; bringing together astronomers, biologists, chemists, geologists, and physicists, to answer these fundamental questions about the role of biology in the Universe. NASA’s present search for life beyond Earth prioritizes the search for liquid water: where we find liquid water on Earth, we generally find life. Over the past few decades a major revolution has occurred, shifting our understanding of where liquid water may be found. Moons of the outer solar system such as Europa, Ganymede, and Enceladus orbit the planets Jupiter and Saturn, and though these moons are covered in ice they harbor sub-surface liquid water oceans that contain many times the volume of liquid water found on Earth. These oceans are there today and have likely persisted for much of the history of the solar system, providing key environments in which to search for extant life beyond Earth—life from a possible second, independent origin. Recent discoveries of metabolically active microorganisms in subglacial environments on Earth provides us with a compelling case that sub-ice oceans in the outer Solar System possess the ingredients necessary to support life.
 
 
 
05/27/2014
 
Benjamin Charnay (University of Washington)

Dynamics of Titan's Troposphere and Formation of Equatorial Dunes

 
A major surprise in the exploration of Titan by Cassini was the discovery of large dune fields in the equatorial regions, which cover close to 15% of Titan’s surface. These giant dunes are linear and parallel to the equator, and are probably composed of hydrocarbon material issued from methane photolysis. The analysis of dune morphology around obstacles and dune terminations indicates a global eastward dune propagation. However, Global Climate Models (GCMs) predict easterly (westward) annual mean surface winds over Titan’s equatorial regions, as trade winds on Earth. Therefore, Titan’s dune orientation is opposite to predicted mean winds, raising a major enigma. During this talk, I will show that GCMs are powerful tools to understand the dynamics of Titan's troposphere and I will present a new mechanism for the formation of Titan's dune based on the impact of methane storms.
 
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Regina Carns (University of Washington)

The Influence of Extracellular Polysaccharides on Ions in Sea Ice Brine Pockets (UWAB Research Rotation Presentation)

 
The pockets and channels of brine in sea ice are a rich habitat for bacteria, algae and other microscopic forms of life. Over the course of a winter, as the ice gets colder, these brine pockets get smaller and saltier. Gooey extracellular polysaccharide (EPS) excreted by algae and bacteria may help them deal with these extremes of temperature and salinity, but the interaction of EPS with the physical and chemical environment of the brine pocket is still not fully understood. In this rotation, Regina worked in Jody Deming's lab to process field samples of sea ice to evaluate their EPS content and performed experiments in the lab to see whether ions in seawater would bind to EPS. 
 
(Recording Unavailable)
 
 
06/03/2014
 
Lucianne Walkowicz (Princeton University)

Rise of the Machines: Mining the Kepler Data for Astrobiology

 
Since its launch in 2009, NASA's Kepler Mission has transformed our knowledge of exoplanetary system demographics. Kepler's primary mission goal—to quantify the occurrence rate of habitable zone Earth-size planets around Sun-like stars—has a clear connection to astrobiology. However, in addition to its planet-finding capabilities, the Kepler data may also be used to study other questions of astrobiological interest. In this talk, Lucianne will discuss her work on two such ongoing projects: the quantification of the stellar flare rate, which influences planetary habitability through its influence on atmospheric photochemistry and escape; and the detection of anomalous stellar variability as a form of signal-agnostic optical SETI. Both of these lines of research employ machine learning techniques, making them applicable to the current and future large datasets that now dominate the astronomical landscape.
 

2013

 
10/08/2013
 
Eddie Schwieterman (University of Washington)

Research Rotation Talk:  From Microbiology to Radiative Transfer: Investigating the Spectral Reflectance of a Cross-section of Microrganisms on Earth and the Possible Implications for Surface Reflectance Biosignatures on other Earth-like Worlds

 
Investigations of the possible remotely detectable surface reflectance biosignatures on Earth-like planets focus on analogies to the vegetation red edge and “green bump” spectral features on Earth. Inherent in these studies are assumptions regarding types of organisms and the function of pigments that may produce these discernible features. We present in vivo visible reflectance spectra of a cross section of pigmented microorganisms with various evolutionary histories to illustrate to the spectral diversity of biologically produced pigments on Earth.  These spectra are compared quantitatively with those of red-edge producing land plants. We use synthetic broadband colors to show a significant spread in color space of pigmented organisms compared to common planetary surface types (soil, snow, ocean, etc.). Pigmentation has evolved for multiple purposes other than photosynthesis, including photo-protection and adaptation to extreme environments. We review the prevalence of macroenvironments on Earth that host organisms with non-chlorophyll visible pigmentation, especially the case of pigmented halophiles in hypersaline lakes and ponds. Finally, we explore the detectability of a scenario where a pigmented organism of this type is widespread on an Earth-analog planet.   Eddie worked for three months at the University of Edinburgh and the UK Centre for Astrobiology with Professor Charles Cockell as his rotation supervisor.
 
Also featuring:
 
Peter Driscoll (University of Washington)
 

Topic: Planetary internal processes, magnetism and habitability

 
(Recording Unavailable)
 
 
10/15/2013
 
David Crisp (NASA Jet Propulsion Laboratory)

Measuring Atmospheric Carbon Dioxide from Space – the NASA Orbiting Carbon Observatory-2 (OCO-2)

 
Fossil fuel combustion, deforestation, and other human activities are now adding more than 35 billion tons of carbon dioxide (CO2) to the atmosphere each year. These emissions are superimposed on an active natural surface-atmosphere carbon cycle that exchanges more than 20 times as much CO2 each year, and is currently absorbing about half of the human emissions. The existing greenhouse gas network provides an accurate integral constraint on the net global CO2 emissions and trends, but does not have the resolution or coverage needed to quantify natural CO2 fluxes or discriminate human CO2 emissions from the natural background on regional scales. The Orbiting Carbon Observatory – 2 (OCO-2) is the first NASA satellite designed specifically to address this need. OCO-2 will be launched in July 2014. Once in orbit, its spectrometers will record over a million CO2 soundings each day. Here, we will summarize the OCO-2 measurement approach, status, and plans.
 
(Recording Unavailable)
 
 
10/22/2013
 
Jon Toner (University of Washington)

Liquid Water on Mars Down to –120°C: Experimental Evidence for Supercooled Brines and Low-Temperature Perchlorate Glasses

 
Life as we know it requires liquid water, but on Mars pure liquid water is unstable due to extremely cold, dry, and low pressure conditions.  A way in which water could be stabilized on Mars is in concentrated salt solutions, which lower the freezing point of water.  The maximum equilibrium freezing‑point depression possible for a given salt solution is the eutectic temperature, ranging from near 0°C for carbonates and sulfates to as low as –75°C for perchlorates.  Eutectic temperatures suggest a lower temperature limit for liquid water on Mars; however, salt solutions will typically supercool below their eutectic before crystallization occurs.  Our research into supercooled MgSO4, MgCl2, NaCl, and NaClO4 solutions shows that supercooling 5–15°C below the eutectic is common.  Remarkably, we have found that Mg(ClO4)2 and Ca(ClO4)2 solutions never crystallize during slow cooling, but remain in a supercooled, liquid state until forming an amorphous glass near –120°C, even when mixed with soil.  Large supercooling effects have the potential to prevent water from freezing over diurnal and possibly annual cycles on Mars.  Furthermore, low-temperature glasses are potentially important for astrobiology because of their far greater ability to preserve pristine cellular structures compared to solutions that crystallize.
 
(Recording Unavailable)
 
 
10/29/2013
 
John Schutt (Haughton-Mars Project)

Meteorites and Ice - A Cosmic Cocktail

 
Antarctica has been a prolific source of meteorites since the discovery of large numbers of specimens in the 1970's. Nearly 50,000 specimens have since been recovered from the icy continent. "Meteorites and Ice - A Cosmic Cocktail" tells the story of the importance of meteorites to the understanding of our solar system and the U.S. expeditions that travel to Antarctica to search for them.
 
 
 
11/05/2013
 
Zachary Adam (Montana State University)

Once More Unto the Evolutionary Breach: Microfossils and the Mesoproterozoic Rise of Complexity

 
The Mesoproterozoic has been referred to as the dullest time in Earth’s history. However, rocks from this period contain some of the earliest evidence available of a leap made across a great evolutionary chasm: the emergence and diversification of eukaryotes in a prokaryote-dominated world. Here we present newly discovered protistan-grade microfossils from the 1.45 billion-year-old Belt Supergroup of Montana. These include forms that grade within and between different morphological groups, providing tentative clues to the reconstruction of ontogenetic, reproductive or ecophenotypic variation signals of the original organisms. This microfossil assemblage and others of similar age present a unique opportunity to explore the emergence, development, ecology and evolutionary biology of some of Earth’s oldest eukaryotes. Precambrian micropaleontology, in conjunction with molecular biomarker, stable isotope and paleoenvironmental data, is critical for assessing the extent to which we may use paleobiology to infer the likelihood of finding complex life on extrasolar planets.
 
(Recording Unavailable)
 
 
11/12/2013
 
Melissa Rice (Callifornia Institute of Technology)

The New Colors of the Red Planet: Reflectance Spectroscopy and the Habitability of Ancient Mars

 
Reflectance spectroscopy is currently revolutionizing our understanding of Mars’ environmental history and habitability. The traditional view of Mars’ unidirectional evolution from an early warm, wet environment to a younger cold, dry environment no longer holds; new, high-resolution orbital data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is revealing the importance of local alteration environments and potential niches for habitability on small spatial and temporal scales. Here I will discuss Gale Crater as a case study for this emerging view of complexity in ancient aqueous environments on Mars, and the implications for habitability. From orbit, CRISM has discovered a complex stratigraphy of phyllosilicate, sulfate and iron oxide minerals. On the ground, reflectance spectra from the Curiosity rover’s Mastcam instrument reveal centimeter-scale distributions of hydrated minerals, in addition to minerals that formed in a variety of redox states, with colors never before seen on the surface of Mars.
 
 
 
11/19/2013
 
Chris Glein (Carnegie Institution of Washington)

Organic Geochemistry: From Hydrothermal Vents on Earth to the Great Lakes of Titan

 
Organic compounds are degraded and synthesized in hydrothermal systems on Earth. For example, the degradation of organic matter in sedimentary environments leads to the formation of petroleum; while abiotic organic synthesis may occur in hydrothermal vents, which may play a critical role in the origin of life. The key to understanding these important processes is to understand the detailed reaction mechanisms, particularly how carbon-carbon bonds can be broken and formed under geochemically relevant conditions. I will show how experiments guided by principles of physical organic chemistry have significantly improved our understanding of decarboxylation and abiotic CO2 fixation. In the second half of this talk, I will introduce the new field of cryogenic fluvial geochemistry, as applied to Saturn's planet-like moon, Titan. Liquefied natural gases are present on Titan's surface, most famously as lakes. Solid organic compounds are also thought to be widespread as a result of deposition from the atmosphere. A fundamental question is: What kinds of geochemistry can occur when these materials meet? I will show how thermodynamic modeling can be used to calculate the solubilities of organic minerals in the cryogenic hydrocarbon solvents on Titan. Despite the extreme differences in physical and chemical conditions on Titan and Earth, we will discover intriguing parallels in the fluvial geochemistry of the only wet worlds in the Solar System.
 
 
 
11/26/2013
 
Matthew Pasek (University of Southern Florida)

An Early Earth Predisposed to Phosphorylation of Organics

 
The element phosphorus is important in the development and possibly origin of life on the earth. The formation of phosphorylated organics, such as those found in all life today, does not occur easily under plausible prebiotic conditions. Here I present new results on the chemistry of phosphorus in the Archean as sampled from the 3.52 billion year old limestone that shows a fundamental difference between archean phosphorus and the modern phosphate cycle. Additionally, I will show how these differences could have influenced the prebiotic chemistry of early environments from a "just add water" perspective.
 
 
 
12/03/2013
 
Drew Gorman-Lewis (University of Washington)

Ammonia Oxidizing Archaea Survival Mechanisms in Low-Nutrient Environments

 
The ammonia-oxidizing archaeon (AOA) Nitrosopumilus maritimus strain SCM1 (N. maritimus strain SCM1), a representative of the Thaumarchaeota archaeal phylum, can sustain high specific rates of ammonia-oxidation at ammonia concentrations too low to sustain metabolism by ammonia-oxidizing bacteria (AOB). One structural and biochemical difference between N. maritimus and AOB that might be related to the adaptation of N. maritimus to low nutrient conditions is the cell surface. A proteinaceous surface layer (S-layer) comprises the outermost boundary of the N. maritimus cell envelope, as opposed to the lipopolysaccharide coat of Gram-negative AOB. In this work, we characterized the surface of two archaea having an S-layer with that of four-representative AOB with chemical techniques to evaluate differences in surface reactivities. Since these alternative boundary layers mediate interaction with the local external environment, these data provide the basis for further comparisons of surface reactivity toward essential nutrients. 
 

2012

 
 
12/04/2012
 
Heshan Illangkoon (Blue Marble Institute of Science)

Making Time for Astrobiology Outreach: How teaching English through Astrobiology in East Africa led to the Astrobiology e-mentoring network, SAGANet.org-- and how you can get involved!

 
A three month volunteer trip in East Africa to teach in an English language class and start a non-profit micro-finance NGO (www.investours.org) took an interesting turn when an element of astrobiology outreach was introduced. Instead of strictly teaching English, students in the language class were taught English through astrobiology and science. Their curiosity and drive for knowledge increased and even encouraged some students to resume formal schooling through the aid of sponsorship. Upon returning to the United States a year later, this experience was presented at the 2011 Astrobiology Graduate Conference. The collaborative nature of this conference drew five colleagues together to harness the power of astrobiology outreach and to reach a wider, international audience. The result is the eMentoring web-portal for astrobiology S.A.G.A.N. (Social Action for a Grassroots Astrobiology Network – www.SAGANet.org). Launched in April 2012, with the support of the NASA Astrobiology Institute and the Carl Sagan Foundation, the S.A.G.A.N. network enables a mentoring relationship to be formed between scientists and students with interests in astrobiology and the space sciences with the goal of fostering interest in STEM (science, technology, engineering & mathematics) field education. The S.A.G.A.N. site contains collaboration tools including group video chat, live streams of astrobiology related seminars & conferences, hosts a weekly book club and monthly salon discussion on the philosophy of science among other topics. If you are an astrobiologist or simply have an interest in the field we invite you to join SAGANet.org today!
 
 
 
11/27/2012
 
David Brain (UC Boulder)

Do Magnetospheres Matter?

 
A planet's atmosphere is the net result of source and loss processes acting on it over time. One of the more poorly constrained processes in terms of its role in changing atmospheric abundance is 'escape to space'. This suite of mechanisms, where atmospheric particles are driven from the top of the atmosphere, is often thought to be more efficient at planets lacking global magnetic fields (such as Mars) than at planets with global dynamo magnetic fields (such as Earth) because the solar wind can directly encounter the atmospheres of unmagnetized planets. Thus, it is argued that escape to space could have resulted in the removal of significant amounts of an early Martian atmosphere. We will review the current understanding and outstanding questions about escape to space at Mars, and then discuss whether the presence of a global dynamo magnetic field should significantly influence a planet's climate and habitability. Applications of these concepts to other planets in our solar system and beyond will be discussed.
 
 
 
11/20/2012
 
Boswell Wing (McGill University) - CANCELED
 
 
11/13/2012
 
Dorian Abbot (University of Chicago)

Indication of Insensitivity of Planetary Weathering Behavior and Habitable Zone to Surface Land Fraction

 
It is likely that unambiguous habitable zone terrestrial planets of unknown water content will soon be discovered. Water content helps determine surface land fraction, which influences planetary weathering behavior. This is important because the silicate-weathering feedback determines the width of the habitable zone in space and time. Here a low-order model of weathering and climate, useful for gaining qualitative understanding, is developed to examine climate evolution for planets of various land-ocean fractions. It is pointed out that, if seafloor weathering does not depend directly on surface temperature, there can be no weathering-climate feedback on a waterworld. This would dramatically narrow the habitable zone of a waterworld. Results from our model indicate that weathering behavior does not depend strongly on land fraction for partially ocean-covered planets. This is powerful because it suggests that previous habitable zone theory is robust to changes in land fraction, as long as there is some land. Finally, a mechanism is proposed for a waterworld to prevent complete water loss during a moist greenhouse through rapid weathering of exposed continents. This process is named a “waterworld self-arrest,” and it implies that waterworlds can go through a moist greenhouse stage and end up as planets like Earth with partial ocean coverage. This work stresses the importance of surface and geologic effects, in addition to the usual incident stellar flux, for habitability.
 
 
 
11/06/2012
 
Sanjoy Som (NASA Ames Research Center)

A coupled geochemical-bioenergetic model to constrain the potential for methanogenesis in serpentinizing systems

 
The likely presence of liquid water in contact with olivine-bearing rocks on Mars, the detection of serpentine minerals and of methane emissions possibly consistent with serpentinization, and the observation of serpentine-associated methane-cycling communities on Earth have all led to excitement over the potential of such systems to host life on Mars, even into the present day. However, the habitability of subsurface serpentinizing systems on Mars does not necessarily follow from these qualitative observations. In particular, while the production of H2 during serpentinization could provide methanogens with a needed substrate, the alkaline conditions and corresponding potential for carbon limitation that arise in concert are negatives against which H2 supply must be balanced. We consider this balance via a coupled geochemical-bioenergetic model that weighs the outputs of serpentinization against the metabolic requirements of methanogenesis, in an energetic frame of reference.
 
 
 
10/30/2012
 
Marshall Reeves (Princeton University)

Interrogating the DNA of arsenate-grown GFAJ-1 cells: tools, techniques, and data

 
A strain of Halomonas bacteria, GFAJ-1, has been claimed to specifically incorporate arsenic into its DNA in place of phosphorus. However, two groups using complementary methods concluded that GFAJ-1 DNA contains no covalently bound arsenate. The techniques applied are broadly applicable to novel or non-canonical organisms and thus especially suited for any astrobiologist's toolkit.
 
 
 
10/23/2012
 
Sara Walker (Arizona State University)

The Algorithmic Origins of Life

 
The origin of life is arguably one of the greatest unanswered questions in science. A primary challenge is that without a proper definition for life – a notoriously challenging problem in its own right – the problem of how life began is not well posed. Here we propose that the transition from non-life to life may correspond to a fundamental shift in causal structure, where information gains direct, and context-dependent, causal efficacy over matter, a transition that may be mapped to a nontrivial distinction in how living systems process information. We discuss potential measures of such a transition, which may be amenable to laboratory study, and how the proposed mechanism corresponds to the onset of the unique mode of (algorithmic) information processing characteristic of living systems.
 
 
 
10/16/2012
 
Cecilia Bitz (University of Washington)

Modeling the Climate of Exoplanets with GCMs

 
(Abstract Unavailable)
 
(Recording Unvailable)
 
 
10/09/2012
 
Kyle Costa (University of Washington)

Influence of Precipitation on the Movement of Salts Through Hyper-Arid Desert Soil

 
(Abstract Unavailable)
 
(Recording Unavailable)
 
 
05/29/2012
 
John Armstrong (Weber State University)

Sixty Minutes to Near-Space: Using High Altitude Ballooks as Inexpensive, Mission-driven Experiences in the Space Sciences

 
For the past three years, Weber State University has been using inexpensive high altitude balloons to access extreme atmospheric environments above 100,000 ft. The High Altitude Reconnaissance Balloon for Outreach and Research (HARBOR) is a student-led team of engineers and researchers that provides a platform for exploration of the atmosphere from the surface to altitudes approaching 125,000 feet. These balloon systems are designed, constructed and flown by the students themselves. They are inexpensive to construct, are built with common electronic and hardware components that are easily purchased from commercial vendors, and can be launched and recovered in a single day. The systems are reusable and can be flown many times, allowing students to fly many new experiments during their student lifetime, or to fly a single experiment many times to acquire extended scientific data sets. I'll discuss the results of the last three successful flight seasons, and give an overview of how students and faculty can partner to start a high-altitude ballooning program for experimental access to Mars-like environments and other ideas for using balloons to support mission-driven experiments in astrobiology.
 
 
 
05/22/2012
 
Jeff Bowman (University of Washington)

Teaching the Teachers: Integrating Astrobiological Concepts into Secondary Education by Reaching Teachers at the Masters Level

 
I will present a course, "Fundamentals of Astrobiology for Science Educators," that was offered at UW Bothell in the fall of 2010. The course emphasized how astrobiology can be used as a bridge to link science concepts typically viewed as unrelated by students and was designed to provide practicing educators with a working overview of key astrobiological concepts within the context of state and national science education standards. We used a combination of lectures, discussions, and classroom activities to help the students integrate astrobiology with their existing curriculum.
 
(Recording Unavailable)
 
 
05/15/2012
 
Lucas Mix (University of Arizona)

The Meaning of "Life": Astrobiology and Philosophy

 
Usually when we speak of the "meaning of life" it has hints of religion associated (or at least Monty Python). The rather abstract question, however, has some very concrete elements based in science. What is the context in which we find life? How do living things relate to one another and to their environment? Our philosophy - particularly our notions of how we know things and what things are talking about - allow us to tie these basic empirical questions into a greater understanding of the universe and ourselves. The talk will explore where the lines are between science, philosophy, and fundamental meaning, particularly in regards to how we define "life."
 
 
 
05/08/2012
 
Bethany Ehlmann (California Institute of Technology)

The Earliest Aqueous, Habitable(?) Environments on Mars: A View from Orbit

 
The emerging picture of Mars' first billion years includes diverse environments involving liquid water and chemical alteration. Clay, carbonate, chloride, and sulfate minerals have all been detected and mapped from orbit in coherent geologic units. When near-infrared spectroscopic detections of minerals from the orbiting CRISM imaging spectrometer are coupled with high-resolution images of morphology provided by orbiting cameras, distinctive aqueous, potentially habitable, environments can be identified, preserved in the geologic record. I will give a global overview of the most recent findings, delve into the details of transitions recorded in a few key stratigraphic sections, and discuss the hypothesis that the most widespread and long-lived aqueous environments on early Mars were in the subsurface.
 
 
05/01/2012
 
Everett Shock (Arizona State University)

Geochemistry Meets Biochemistry in Hydrothermal Ecosystems

 
I will ponder how we can move from the traditional geochemical framework of water-rock reactions to the more inclusive and realistic water-rock-organic-microbe processes, and how all of this might be modeled. The focus will be on recent experimental work (largely on recent field work in Yellowstone) and the insights gained from theoretical analysis.
 
 
 
04/24/2012
 
Antigona Segura (Instituto de Ciencias Nucleares))

Tales of Habitability: The Curious Case of M Dwarf Planets

 
As we discover more exoplanets and improve our observational techniques, we are moving closer to finding planets that are potentially habitable. M dwarfs (main sequence M stars) are the most numerous in the Solar neighborhood. They are also the stars around which it is easiest to detect a rocky planet using the radial velocity method with instruments on the ground. However, these stars also have characteristics that may be harmful for life in planets around them. In this talk I will present the characteristics of M dwarfs, the conditions required for surface habitability, the concept of biosignatures, and review the research on habitability and life detection on rocky planets around M dwarfs.
 
 
 
03/27/2012
 
Dirk Schulze-Makuch (University of Washington)

The Future of Human Life: Mars, Exoplanets, and the 100-year Starship Project

 
One of the major goals of NASA's Astrobiology Roadmap is to gain insights on the Future of Life. We realize that we are living on a vulnerable planet in a dangerous universe. One solution to make us less vulnerable from catastrophes is to enhance space exploration and ultimately colonize other worlds. The obvious choice is Mars due to its close proximity and available resources. An alternative option is explored by the recent DARPA/NASA initiative for a 100-year Starship Project: to develop the capability to travel to planets outside of our solar system within 100 years. A priority-scheme is introduced of how to determine which of the more than 700 confirmed exoplanets so far may be habitable. The scheme supports the 100-year Starship Project and helps focusing future investigations on which of the exoplanets we might find life.
 
 
 

2011

 
11/15/2011
 
David Des Marais (NASA Ames Research Center)

Exploring Mars for Evidence of Habitable Environments and Life

 
To search for evidence of life, we must first identify landing sites where environmental conditions had been favorable for life or its chemical precursors. Those conditions must also have favored the geological preservation of any remains. The Mars Exploration Rovers found deposits from evaporated saline water bodies and hydrothermal systems; such environments might have been habitable. The rovers identified sulfates, carbonates and silica; these mineral groups can preserve evidence of environments and life. Spirit rover found ultramafic rocks (Fe- and Mg-rich, relatively Si-poor); these can react with water to produce hydrogen and other products that can sustain microbes. Both Spirit and Opportunity found evidence that subsurface liquid water had persisted sometime in the distant past. Recent orbital observations of phyllosilicates (clay minerals) also indicate the former presence of near-surface water. These diverse, extensive sedimentary deposits indicate that ancient Mars hosted a wide variety of potentially habitable aqueous environments.
 
 
 
11/01/2011
 
Kevin Walsh (Southwest Research Institute)

How the Migration of Jupiter Shaped the Inner Solar System: "The Grand Tack"

 
A persistent difficulty in terrestrial planet formation models is creating Mars analogs with the appropriate mass: Mars is typically an order of magnitude too large in simulations. A recent work found that a small Mars can be created if the planetesimal disk from which the planets form has an outermost edge at 1.0 AU. However, this work and no previous work, can explain such a truncation of the planetesimal disk and preserve the asteroid belt. We show that gas-driven migration of Jupiter inward to 1.5 AU, before its subsequent outward migration, can truncate the disk and repopulate the asteroid belt. This dramatic migration history of Jupiter suggests that the dynamical behavior of our giant planets was more similar to that inferred for extra-solar planets than previously thought, as both have been characterized by substantial radial migration.
 
 
 
10/18/2011
 
Robert Tyler (NASA Goddard Space Flight Center)

The Importance of Tidal Flow in Maintaining an Abundance of Liquid Oceans in the Universe

 
(Abstract Unavailable)
 
 
 
04/19/2011
 
Mathew T. Hurtgen (Northwestern University)

The Role of Sulfur in Regulating Earth Surface Oxygen Levels

 
Several lines of evidence suggest that Earth surface oxygen levels increased ~2300 years ago. While oxygen concentrations through the remainder of the Proterozoic (2500-542 million years ago) are poorly constrained, recent studies have linked an increase in the abundance of redox-sensitive elements and the difference between sulfur isotope ratios measured in sedimentary sulfate and contemporaneously deposited pyrite to a second oxy genation event ~580 million years ago—coincident with the diversification of macroscopic metazoa. Sulfur isotope data from the early Neoproterozoic Bitter Springs Formation, Australia suggests an increase in microbial sulfide production in anoxic marine bottom waters and sediments may have enhanced nutrient recycling, thus sustaining elevated organic carbon burial rates and early Neoproterozoic oxidation. These findings are consistent with evidence of eukaryotic diversification at this time and suggest that oxidation of the atmosphere-ocean system occurred earlier in the Neoproterozoic than previously appreciated. These results highlight the role that sulfur plays in regulating the exogenic cycles of carbon and oxygen, particularly in low sulfate oceans of Earth's past.
 
 
 
04/12/2011
 
Nicholas V. Hud (Georgia Institute of Technology)

A Self-Assembly Approach to the Proto-RNA World

 
Most current scientific theories for the origin of life contain the implicit assumption that RNA came before DNA and coded proteins. However, just how the first RNA polymers would have assembled and replicated without the aid of protein enzymes remains an open question. We have hypothesized that a proto-RNA came before RNA, and that the first RNA-like polymers contained chemical building blocks that were functionally similar to the contemporary building blocks of RNA, but distinct in that they were capable of forming low energy covalent bonds that facilitated polymer formation. We have also hypothesize that prebiotic molecules similar to molecules known today to intercalate contemporary nucleic acids, which we have termed 'molecular midwives', facilitated the assembly of RNA-like polymers by acting as nanometer-scale surfaces that templated base pair formation. This self-assembly approach to the origin of proto-RNA is showing promise in laboratory experiments, and providing possible solutions to long-standing problems associated with the prebiotic synthesis of RNA.
 
(Recording Unavailable)
 
 
04/05/2011
 
Brent C. Christner (Louisiana State University)

Subglacial Environments: The Other Deep Biosphere

 
Although glaciers and ice sheets have conventionally been viewed as environments inhospitable for life, recent work has documented viable microorganisms in ancient ice cores and it is estimated that ~10^24 prokaryotic cells are archived globally in glacial ice. Liquid water is abundant beneath the Antarctic ice sheets and the subglacial aquifer volume is thought to be at least 107 km3. Based on available data from the ice and sediments, the subglacial environment of Antarctica may harbor ~10^29 prokaryotic cells, which equates to ~4.5 petagrams C and is ~20% of that reported for all surface soils on Earth. This new vision of life in the polar regions has provided an informed perspective to define the boundaries of the biosphere and extrapolate the likelihood of life surviving and persisting on icy planets and moons in the solar system and beyond.
 
 
 
03/29/2011
 
Jenn Macalady (Pennsylvania State University)

A Rainbow of Ocean States

 
Recognizing the many links between biogeochemical reactions and the uncharacterized microorganisms populating the oceans, microbiologists have undertaken a major effort in the past decade to explore the marine microbial biosphere. Meanwhile, many earth scientists now view ocean chemistry as highly dynamic on geologic time scales, reflecting changing inputs and outputs as Earth and life co-evolved. Research at an emerging network of ancient ocean analog sites is poised to improve our knowledge of changes in past ocean states, partly by revealing how we should interpret hopanoid and carotenoid biomarkers for marine phototrophs. Our long-term goal is a mechanistic understanding of interactions between physical and chemical factors and the ecology of anoxygenic and oxygenic phototrophy, including biosignatures.
 
 
 

2010

 
12/07/2010
 
Mark Skidmore (Montana State University)

The (Sub)glacial Biosphere: Microbial Activity at Zero Degrees Celsius and Below

 
Ice is an abundant phase of water in the solar system, however, we are currently limited in our knowledge of in situ microbial activity in icy environments, specifically in subglacial systems and in glacial ice. Glaciological processes under ice masses, including ice sheets, produce conditions favorable for microbes by forming subglacial aquatic environments through basal melting and providing nutrients and energy for microbes from bedrock comminution. Microbes have been found in subglacial waters, subglacial sediments and basal ice from all types of glacial systems and certain types of organism demonstrated as active in laboratory cultures in simulated in situ conditions (dark, 0-4oC). Subglacial microbial activity has also been inferred from geochemical and isotopic analyses of glacial meltwaters. Further, culture independent analyses of subglacial microbial communities suggest selection for certain types of organism based on available energy sources. Microbial activity in debris rich basal ice has also been inferred from gas analyses, and laboratory studies have shown microbial activity in ice at sub freezing temperatures. Current findings will be discussed and their implications for future astrobiological investigations.
 
 
 
 
Christophe Sotin (Jet Propulsion Laboratory / California Institute of Technology)

The Habitability of Icy Moons

 
The icy moons contain several of the ingredients required for habitable worlds including water, organics and energy. This talk first reviews the lines of evidence leading to the conclusion that a liquid water layer is present in the interior of Europa, Callisto, Ganymede, Enceladus and Titan. Then, the fate of organics on Titan is described at the light of recent Cassini observations. Finally, the importance of tidal energy is briefly discussed.
 
 
 
10/19/2010
 
Jim Kasting (Pennsylvania State University)

Atmospheric Composition and Climate on the Early Earth

 
Earth's climate has remained relatively warm during most of its history even though the Sun was considerably fainter in the distant past. Higher concentrations of greenhouse gases, especially CO2, CH4, and NH3 (shielded by fractal organic haze), in the past are probably required to explain this warmth, although albedo feedbacks could have played a role, as well. The recent paper by M. Rosing et al. (Nature, 2010) suggests, surprisingly, that atmospheric CO2 concentrations during the Archean Era were no more than 3 times higher than today, based on analysis of banded iron-formations, and that cloud feedbacks caused by changes in biogenic sulfur gas fluxes were the key to keeping the Earth warm. I will argue that Rosing et al. are wrong and that atmospheric CO2 concentrations were considerably higher than they specify.
 
 
 
06/01/2010
 
Matt Pasek (University of South Florida)

High Energy Processing of Phosphorus on the Early Earth

 
Phosphorus is a key element in biology, and may have been critical to the origin or early evolution of life on the Earth. Reduced oxidation state phosphorus compounds have been shown recently to generate potentially prebiotic compounds. These compounds are demonstrated to form in lightning strikes, and possibly in rocks affected by impact.  I will review how high energy processes change the oxidation state of phosphorus and the eventual fate of these compounds on the early Earth.
 
 
 
05/25/2010
 
Dawn Sumner (University of California, Davis)

Microbial Mat - Environment Interactions in Lake Joyce, Antarctica, and Implications for Archean Microbialites

 
Microbial mats in ice covered lakes in Antarctica developed in an environment with little disruption from currents or grazing.  Thus, their growth morphology more directly reflects microbial processes than many stromatolites and other microbialites.  However, the history of lake level rise and sedimentation also influenced microbialite morphology.  I will discuss our on going project to constrain microbial processes that influence morphology and how results provide insight into interpretations of Archean microbialites.
 
 
 
05/11/2010
 
Antonio Lazcano (Universidad Nacional Autonoma de Mexico)

The 1953 Miller Experiment and the Origins of Life: The Ghosts Behind the Molecules

 
The heterotrophic origin of life proposed by Oparin and Haldane in the 1920's was part of a Darwinian framework that assumed that living organisms were the historical outcome of a gradual transformation of lifeless matter. This idea was strongly opposed by the geneticist H. J. Muller, who argued that single genes or DNA molecules represented primordial living systems. Their debates represent not only contrasting views of the nature of life itself, but also major ideological discussions that reached a surprising intensity in the years following the 1953 Miller experiment, which demonstrated the ease with which organic compounds could be synthesized under putative primitive conditions. During the years following the Miller experiment, attempts to understand the origin of life were shaped scientifically by the development of molecular biology and, in socio-political terms, by the atmosphere created by Cold War tensions.
 
 
 
04/20/2010
 
David Kring (USRA - Lunar and Planetary Institute)

Lunar Impact Cataclysm: Implications for Astrobiological Conditions Throughout our Solar System & in Other Planetary Systems

 
Analyses of Apollo samples of the Moon and meteoritic samples of asteroids suggest there was an intense period of impact bombardment ~3.9-4.0 Ga, several hundred million years after solar system formation. The geochemical and geologic fingerprints of that period of bombardment point to asteroids as the principal source of the debris. The data suggest Jupiter's orbit moved, causing resonances to sweep through the asteroid belt. The bombardment may have made life untenable on the surfaces of planets (including Earth), while simultaneously creating subsurface habitats.  Similar periods of bombardment in other planetary systems are being detected by the Spitzer Space Telescope.
 
(Recording Unavailable)
 
 
04/06/2010
 
Webster Cash (University of Colorado, Boulder)

Starshades and Direct Observation of Exoplanets

 
The last ten years have seen truly amazing strides towards understanding the nature of exoplanetary systems. But the techniques that have been so productive at discovering planets are highly limited in what they can tell us about their natures. For that we will need direct imaging and spectroscopy. When we turn the full suite of astronomical instruments, including photometry, spectroscopy and polarimetry on exoplanets we will be able to analyze atmospheres and surfaces and search for unambiguous biomarkers. Starshades, or external occulters as they are more formally known, can suppress light from the central stars and reveal exoplanets into the Habitable Zone. I will review how starshades work, the status of their technical development and how well they can advance observational astrobiology. In particular, I will show how coordinated use of starshades with the James Webb Space Telescope can allow us to find and analyze Earth twins in the coming decade at a price that NASA can afford.
 
 
 

2009

 
12/08/2009
 
Loren Williams (Georgia Institute of Technology)

Where Did Protein Come From?

 
Ribosomes are RNA-based macromolecular machines responsible for the synthesis of all proteins in all living organisms. Ribosomes are the most ancient of life's macromolecules and are our most direct link to the deep evolutionary past, beyond the base of the phyologenetic tree. The recent availability high resolution 3D structures of ribosomes provides us with new methods of detection and inference. We will discuss methods for resurrection and biochemical characterization of aboriginal ribosomes.
 
 
 
12/01/2009
 
Nancy Kiang (NASA Goddard Institute for Space Studies)

Efficiency of Photon Energy Use for Life Processes: Implications for Spectral Biosignatures

 
Chlorophyll a (Chl a) is known as the producer of the two unequivocal signs of life observable at the planetary scale: atmospheric oxygen (in the presence of liquid water) and the reflectance spectrum of plant leaves, in which strong absorbance by Chl a in the red contrasts with scattering in the near-infrared. However, a cyanobacterium, Acaryochloris marina, was recently discovered to utilize chlorophyll d (Chl d) in place of Chl a, to absorb light at much longer wavelengths in the far-red and near-infrared, yet still able to perform oxygenic photosynthesis. A. marina lives in an environment depleted in visible light and enriched in the far-red/near-infrared. This talk presents rationale for measurements currently under way of efficiency of photon energy use in A. marina via pulsed, time-resolved photoacoustic calorimetry (PRTPA). Interpretations of potential results are discussed. This rare variation on oxygenic photosynthesis provides the opportunity to probe the efficiency limits of photon energy use for this process, and whether there is an upper bound on useful photon wavelengths. Answering this question will help constrain the plausible signatures of photosynthesis on extrasolar planets where life is adapted to a different parent star. To what extent are photosynthetic pigment absorbance spectra due to the light environment versus due to molecular mechanisms? What is the minimum energy requirement to produce the essential products for growth? Could extrasolar photosynthesis improve on the efficiency found on Earth, or must it be Earth-like after all?
 
 
 
11/10/2009
 
Kevin Hand (Jet Propulsion Laboratory)

Joule Heating of the South Polar Terrain on Enceladus

 
The plumes and observed heat flux in the South Polar Terrain of Enceladus remain a considerable mystery. We report that Joule heating in Enceladus - resulting from the interaction of Enceladus with Saturn's magnetic field - may account for several, to a few tens of megawatts of power across the observed "tiger stripe" fractures. Electric currents passing through subsurface channels of low salinity and just a few kilometres in depth could supply a source of power to the South Polar Terrain, providing a small but previously unaccounted for contribution to the observed heat flux and plume activity.
 
(Recording Unavailable)
 
 
11/03/2009
 
Chris McKay (NASA Ames Research Center)

Results from the Mars Phoenix Mission for Mars Habitability and Comparisons to Mars-like places on Earth

 
Phoenix investigated soil and ice in the martian polar regions. The results of this mission and a comparison with Mars-like sites on Earth provide a basis for considering the limits of life and the possibility of life on Mars in the recent or distant past. Mars-like sites on Earth include arid deserts and the polar regions. Studies of the dry permafrost in Antarctica suggests that the Phoenix site may have been habitable as recently as 5 Myr ago.
 
 
 
10/27/2009
 
Jade Bond (Lunar and Planetary Laboratory)

The Diversity of Extrasolar Terrestrial Planets

 
The details of the formation of the terrestrial planets are long-standing questions in the geological, planetary and astronomical sciences, with the discovery of extrasolar planetary systems placing even greater emphasis on these questions. To date, very little has been done on combining detailed chemical abundance and distribution models with specific planetary formation simulations. Here we present simulations of the bulk compositions of the terrestrial planets and planetesimals in known extrasolar planetary systems. We find that the terrestrial planets produced vary from resembling the planetary composition of the Solar System to being enriched in Ca and Al, Fe or biogenic species such as O, P and C. These enrichments can be taken to the extreme to produce planets unlike anything previously observed.
 
 
 
10/20/2009
 
Steven Benner (The Foundation for Applied Molecular Evolution)

Understanding the Origin of Life

 
This talk will consider genomics, organic chemistry, and planetary science as we try to understand how the first Darwinian chemical systems arose.
 
 
 
05/19/2009
 
Dirk Shulze-Makuch (Washington State University)

Mars, Venus, and What's Life Got To Do With It

 
Both Mars and Venus had large amounts of liquid water on their surface early in Solar System history. Life might have originated on them, and may still persist there despite extreme environmental conditions today. The case for life can be made the strongest for Mars. Life may even exist near the Martian surface by using an intracellular mixture of hydrogen peroxide and water enabling the putative microorganisms to take up water directly from the atmosphere and being freeze-resistant. Some of the Viking mission results support this hypothesis, but further testing with future missions is needed. In the last part of the talk I venture further out and discuss the possibility of more exotic life in places such as Titan, and wrestle with the question of intelligent extraterrestrial life.
 
(Recording Unavailable)
 
 
05/05/2009
 
Felisa Wolfe-Simon (Harvard University)

Geobiochemistry and Evolutionary Metallomics: The Evolution of Life and the Biochemical Consequences of Earth History

 
My research seeks to address geologically informed hypotheses to unravel the biogeochemical co-evolution of Life and Earth. Specifically, I employ extant photosynthetic autotrophs, both cyanobacteria and algae, to probe the evolution of metalloenzymes and their related biochemical pathways. This type of inquiry bridges biology, chemistry, and geology. Currently, the questions driving my research include: 1) Did trace metal availability as driven by changes in oxygen support the dominance of cyanobacteria during a substantial amount of Earth's early history? 2) How did the redox conditions of the environment, and thus micronutrient availability, help drive the rise of photosynthetic eukaryotes? Furthermore, why was there a push towards complex eukaryotic life? 3) How does the expression and utilization of metalloenzymes vary? Are there alternative non-metal analogs to metalloenzymes and their respective metabolic pathways? 4) What biogeochemically significant metals are important to aquatic photosynthesis today? 5) How does the expression and utilization of metalloenzymes vary among microorganisms? 6) Does life need metals? This talk will focus on three projects I am involved with that address different aspect of these questions. My examples will include: 1) the significance of Mn to modern and Mesozoic diatoms, 2) cyanobacteria, nitrogen assimilation and the variability of Mo during the Mid-Proterozoic and 3) the affect of Fe and Cu dynamics on life during the Paleoproterozoic. I will also briefly identify my other projects of interest to the Astrobiology community.
 
 
 
04/28/2009
 
Stephen Wood (University of Washington)

Mars Subsurface Warming at Low Obliquity: Potential for Periodic Production of Liquid Water

 
The obliquity of Mars - that is, the tilt of its spin axis relative to its orbital plane - is currently 25° (similar to Earth's 23°). Orbital dynamics calculations show that for the past 3 Myr the obliquity has oscillated between 15° and 35°, with a dominant periodicity of 120 kyr. Such large variations - a factor of 10 greater than Earth's obliquity variations - have a significant impact on Mars' climate and the global distribution of volatiles. This talk will focus on what happens during periods of low obliquity when perennial CO2 ice forms at the poles, causing atmospheric collapse. At these times, the thermal conductivity of the regolith can be significantly reduced, trapping the upwelling planetary heat flow beneath a more insulating layer and leading to subsurface warming of 40 K or more. At locations and depths where ground ice or hydrated minerals are present, this mechanism provides a way to periodically generate warm, wet conditions throughout Martian history, including several times within the past 1 Myr.
 
 
 
04/21/2009
 
George Cody (Carnegie Institution of Washington)

Geomimetic Biochemistry: How the Origin of Biochemistry may be Linked to the Earth's Early Abiotic Organic Landscape

 
The emergence of life was a natural consequence of organic chemistry that occurred spontaneously on the early Earth. One of the challenges is to identify a specific environment that provided the capacity to promote chemistry that is identifiably useful to biochemistry. We have been performing experimental research on organic chemistry that may occur in proximity to deep sea hydrothermal environments. Recognizing that it is impossible to run experiments long enough or large enough to capture the full range of chemosynthetic pathways, we adopt the approach of mapping out plausible reaction networks. We have identified a robust chemical network that affords a pathway from inorganic sources of C, N, and S up through the familiar metabolic intermediates and beyond towards amino acids and nucleobases. Many of these reactions are catalyzed well by common transition metal sulfides. We have also identified a plausible source of naturally activated phosphate. How all of this chemistry may have intersected in a single localized environment and how this confluence may have acted as a focal point for the origin of life will be discussed.
 
 
 
04/07/2009
 
Melissa Trainer (Goddard Space Flight Center)

Abiotic Chemistry, Atmospheric Hazes, Titan, and the Early Earth

 
There are a myriad of uncertainties involved in the question of how life first began on Earth, including understanding what the early environment was like and how organic materials came to be present.  This talk will review some possible modes for the delivery of organic molecules of interest to the Early Earth.  In particular, discussion will focus on the atmospheric chemical synthesis that may have been present.  Photochemistry of trace atmospheric gases may have led to a rich mixture of organics, many of which may have prebiotic functionalities.  Saturn's moon Titan provides an example of a potential view for the Early Earth -- as a hazy world raining organic particles down onto the surface.  Recent laboratory work has explored the properties of organic particles formed in simulated Early Earth atmospheres, and the implications of such a haze layer for the radiation, climate, and chemical environment of the Early Earth will be discussed.
 
(Recording Unavailable)
 
 

2008

 
12/02/2008
 
Tori Hoehler (NASA Ames Research Center)

Quantifying Habitability as Organism/Environment Energy Balance

 
The presence or absence of liquid water provides a useful first screen for habitability but, as presently applied in consideration of life on other worlds, its resolving power is roughly binary ? "possibly" or "probably not". Among a variety of additional constraints on habitability, energy is both universally required by life and also potentially capable of significantly greater than "binary" resolving power. For life on Earth, energy availability not only places boundary conditions on habitability, but also underlies more than a billion-fold variation in volume-normalized biomass across otherwise comparable ecosystems. I will describe: (i) a conceptual framework designed to capture this resolving power by casting habitability as a balance between biological energy demand and environmental energy availability; (ii) a quantitative application of the energy balance approach to examine the habitability of serpentinizing systems with respect to methanogens; (iii) a potential application of this approach for quantifying the habitability of ancient Martian environments.
 
(Recording Unavailable)
 
 
11/04/2008
 
Joshua Bandfield (University of Washington)

A Complex Compositional and Aqueous History of Mars

 
Spectroscopic datasets from orbiters and landers have been used to identify a growing variety of compositions on Mars. Evidence for sedimentary silica, sulfates, carbonates, phyllosilcates, iron oxides, and chlorides indicates a relatively rich and varied Martian aqueous history that is fundamentally changing our understanding of the planet. This increasingly detailed compositional picture can be used to infer the spatial and temporal extent of habitable environments as well as the potential for biological development and its subsequent preservation.
 
 
 
10/07/2008
 
Rory Barnes (University of Washington)

Habitability of Tidally-Locked Terrestrial Exoplanets

 
The first terrestrial-like exoplanets will likely be observed in tight orbits around low-mass stars. Conveniently, planets on these orbits receive about as much starlight as the Earth does from the Sun, and hence have to potential to be habitable. Such planets may also experience significant tidal forces from the star which can result in orbital decay, a specific planetary rotation, and significant internal heating. I describe how these phenomena are likely to impact habitability. In some cases orbital decay may result in planets moving too close to their star for habitability. For planets on non-circular orbits, rotation periods may be similar to the Earth's and hence may produce similar atmospheric circulation patterns. Tidal heating may span the range from zero to well in excess of Io's, and hence can dramatically impact habitability. Further complicating the situation is the presence of additional companions which may drive large oscillations in the magnitudes of these effects. Taken together these processes suggest a scheme for categorizing planetary attributes based on the planetary system's architecture, including a refinement of the prerequisites for planetary habitability.
 
 
 
05/20/2008
 
Andrew Pohorille (NASA Ames Research Center)

Cyanobacteria in a Lunar Environment

 
Can life be transported beyond its planet of origin, and adapted to survive and thrive on the Moon? Can microorganisms be useful for life support and in situresource utilization in a sustained space exploration? These fundamental questions were recently discussed at a workshop that brought together microbiologists, planetary scientists and experts in flight experiments and hardware. The focus was on cyanobacteria as model organisms because of their antiquity on earth, metabolic diversity, resilience to adverse conditions, ability to efficiently produce oxygen and hydrogen, and the existence of advanced capabilities for their genetic manipulation. I will discuss the main findings of the workshop regarding the challenges of and a research program for establishing cyanobacteria in a lunar environment. Such a program will help to connect astrobiology with NASA's missions to the Moon.
 
(Recording Unavailable)
 
 
05/13/2008
 
James Kasting (Pennsylvania State University)

Was the Early Earth Hot?

 
Despite the faintness of the young Sun, the early Earth appears to have been warm, or perhaps even hot. Taken at face value, oxygen and silicon isotopes in ancient cherts imply a mean surface temperature of 70(±15)°C at 3.3 Ga1,2. Ancient carbonates also yield high Precambrian surface temperatures3, as does a recently published analysis of the thermal stability of proteins which are inferred to be ancient4. This evidence for hot early surface temperatures must be weighed against the previously mentioned dimness of the young Sun, as well as geomorphic evidence for glaciation at 2.9 Ga, 2.4 Ga, and 0.6-0.7 Ga. Climate models with high CO2 and CH4 concentrations can potentially explain hot climates, but can they explain climates that transition from hot to cold, and back again, multiple times? Such models must also account for the well documented correlation between the rise of O2 at 2.4 Ga and the Paleoproterozoic glaciations which occurred at that same time. Models that do5 and do not6 rely on changes in seawater oxygen isotopic composition will be discussed.
 
 
 
04/29/2008
 
Jeremy Bailey

Using Polarization to Detect and Characterize Extrasolar Planets

 
Light scattered from planetary surfaces and atmospheres is polarized while the light of the star is unpolarized. The polarization variations around a planet's orbit provide information that is complementary to that obtainable using spectroscopy. I will describe how polarization could be used in the future to search for liquid water on extrasolar terrestrial planets by detecting the rainbow scattering from cloud droplets and the "glint" from surface oceans. Such observations should be feasible with proposed space missions such as the Terrestrial Planet Finder-Coronograph and provide a means of detecting habitable planets. I will also describe a new high-sensitivity polarimeter built to search for the polarized scattered light from Hot Jupiter type exoplanets.
 
 
 
04/22/2008
 
Siegfried Franck

Earth System Analysis: Applications to Astrobiology

 
A general model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the combined ocean and atmosphere reservoir is presented. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex multicellular life. We can calculate the co-evolution of the geo- and biosphere from the Archaean to the long-term future. A simplified Earth system model can be used for the investigation of the habitable zone in the solar system and in exoplanetary systems.
 
 
 
04/08/2008
 
Janet Siefert

Stromatolites: What's Sulfur Got to Do With It?

 
Stromatolites (or more generally, microbialites) are carbonate encased complex microbial communities. They were a mainstream feature of early earth and now are found only in special ecosystems that provide for bacterial domination. This talk describes the bacterial constituency and metabolism within the local context of extant microbialites. We provide evidence that at least one of the conditions for microbialite formation is the presence of sulfur cycle resident in the community. Descriptions such as these better define possible early earth conditions that proved ripe for stromatolite formation and the possibility that we might extend those constraints to the possibilities of similar biotic preservation extra terrestrially.
 
 
 

2007

 
11/20/2007
 
Matthew Pasek

Phosphorus and the Origin of Life

 
Phosphorylated biomolecules like RNA, DNA, ATP, phospholipids, and many coenzymes are critical to life as we know it. Presumably, given their central role in life, phosphorylated biomolecules were also critical for the origin or early evolution of life on the Earth. The origin of these biomolecules remains one of the major questions in origins of life research. Recent discoveries have suggested that the reaction of meteoritic schreibersite with water produces abundant reduced phosphorus compounds which may have encouraged the synthesis of critical prebiotic molecules. The cosmochemistry, geochemistry, and biochemistry of phosphorus will be summarized to point to pathways for the incorporation of phosphorus in the origin of life.
 
 
 
10/23/2007
 
Robert M. Winglee

Upper Atmosphere Interactions Within the Saturn/Titan System

Titan is the only moon in the solar system that is able to maintain a thick atmosphere, with possible oceans of methane and ethane on its surface. This environment is probably the closest facsimile to the early atmosphere on the Earth, albeit at very much lower temperatures. The upper atmosphere is subject to ionization and erosion from incident plasma that is rotating within Saturn's magnetosphere. This interaction can lead to modifications of the optical emissions that is different from the planetary emissions and thereby allow remote sensing of its upper atmospheric conditions. 3-D simulations are used to quantify how the interaction between Titan and Saturn changes under variable solar wind conditions. It is shown that this interaction leads to the generation of a comet-like tail which can extend several Saturn radii in length. This tail can be subject to disruption during storm-like conditions within the planetary magnetosphere. Potential applications to other systems are discussed, including the Jovian system and extrasolar planets.
 
 
 
10/16/2007
 
Sean Raymond

Exotic Earths: Hot Jupiters, Tidal Evolution, and Ocean Planets

Planets like Earth form via collisional accumulation of smaller bodies in circumstellar disks. However, there exist systematic differences between the formation environment of Earth-like planets around other stars and that of the Solar System. For example, short-lived radionuclides (SLRs) like 26Al were an important heat source in the Solar System and may have been derived from a nearby supernova. However, SLRs have variable abundances in protoplanetary disks because of orbital variations within stellar clusters which determine the proximity to supernovae. The quantity of SLRs can be directly tied to the water abundance of terrestrial planets. In addition, the habitable zones of low-mass stars are very close-in, which affects the ability of habitable planets to have large masses or retain water, and can also cause large orbital changes via tidal dissipation. About 60 "hot Jupiters" are currently known; these giant planets likely formed farther from their stars and migrated inward through the habitable zone. Ocean-covered planets are often able to form in the "wake" of a migrating giant planet.
 
 
 
10/09/2007
 
David Crisp (NASA's Jet Propulsion Laboratory)

Measuring CO2 From Space: The Orbiting Carbon Observatory (OCO) Mission

The Orbiting Carbon Observatory (OCO) is currently scheduled for launch in December 2008. This NASA Earth System Science Pathfinder (ESSP) mission will make spatially resolved measurements of CO2 over the sunlit hemisphere the Earth. These measurements will be analyzed with chemical tracer transport models to retrieve CO2 sources and sinks on regional scales and quantify their variability over the seasonal cycle. This seminar will describe the mission objectives, approach, and anticipated products.
 
 
 
10/02/2007
 
Erika Harnett (University of Washington)

Mars: Where Did All The Water Go?

Evidence indicates that Mars was warmer and wetter in the past. In order for water to have been stable, the atmosphere must have been thicker than current conditions. I will discuss possible loss mechanisms in the Martian history, paying particular attention to the mechanisms by which the atmosphere may have been lost to space. I will present results from numerical simulations that show how the loss of the ionosphere to space due to interactions with the solar wind is modulated by both the orientation of Mars' anomalous magnetic field and the solar wind conditions themselves. Studying how the ionospheric loss rate is modulated by solar storms increases the confidence in predictions of past loss rates, as past nominal solar wind conditions are analogous to current day storm conditions.
 
 
 
05/29/2007
 
Joe Kirschvink

Four Billion Years of Climate Change (Lessons from the Precambrian): From Oxygen Poisoning to Snowballs & True Polar Wander

Despite a nearly 30% increase in Solar luminosity over the past 4.5 billion years, the geological record of glaciation appears to have increased, not decreased, over geological time. Investigations indicate that two of the three major Precambrian glacial intervals were exceptionally intense, with solid evidence for widespread glaciers flowing into the oceans on or near the Equator, well within the ice-albedo runaway's "Snowball Earth" zone. These glacial events are also associated with large perturbations in global geochemical cycles, which are reflected particularly well in carbon and sulfur isotopes. The first of these low-latitude glaciations in the early Paleoproterozoic (the Makganyene in South Africa) is also associated intimately with the first solid evidence of global oxygenation, including deposition of the world's largest sedimentary manganese deposit; this hints that the evolution of oxygenic photosynthesis triggered the event by destroying a methane greenhouse. The subsequent low-latitude glaciations during the Cryogenian period of the Neoproterozoic happened about the time that the animal phyla were diversifying, which also suggests organisms were either involved or affected. However, this biological role is complicated by the recognition that large and rapid events of True Polar Wander punctuated Neoproterozoic time, and may have extended sporadically even into the Cretaceous.
 
 
 
05/01/2007
 
Robert M. Hazen

Left & Right: Geochemical Origins of Life's Homochirality 

Life arose on Earth as a geochemical process from the interaction of rocks, water, and gases. Prior to the origin of life, the necessary organic molecules had formed abundantly, but indiscriminately, both in space and on Earth. A major mystery of life's origin is how an idiosyncratic subset of those diverse molecules was selected and concentrated from the prebiotic soup to form more complex structures leading to the development of life. Rocks and minerals are likely to have played several critical roles in this selection, especially as templates for the adsorption and organization of these molecules. Our recent experimental and theoretical studies on interactions between crystals and organic molecules reveal that crystals with chiral surface structures may have facilitated the separation of left- and right-handed biomolecules - the possible origin of life's distinctive homochirality.
 
 
 
02/20/2007
 
Megan Elwood Madden

Gas Hydrates as Planetary-Scale Water and Greenhouse Gas Reservoirs: Implications for Astrobiology

Gas hydrates (clathrates) are plentiful on Earth, forming ice-like gas reservoirs within seafloor sediments and permafrost. Terrestrial gas hydrates may contain more hydrocarbons (natural gas) than all other conventional petroleum reserves combined. However, terrestrial gas hydrate deposits are not unique within the Solar System. Gas hydrates are likely important reservoirs for water and greenhouse gases on other planetary bodies as well, affecting both the availability of water and the composition of planetary atmospheres. Understanding the thermodynamics and kinetics of hydrate formation and decomposition along with the physical properties gas hydrate materials allows us to predict where hydrates are most likely to form in the Solar System and how these gas hydrates may affect the geochemistry and physical processes on planetary bodies. As sources and sinks for carbon and water, the fate of hydrates in planetary systems is intimately tied to the potential for biological activity.
 
 
 
01/30/2007
 
Mark Kuchner

From Carbon Planets to Water Planets: The Composition of Low-Mass Extrasolar Planets

A new extrasolar planet is discovered with mass comparable to that of the Earth. Is it made mostly of silicates like the Earth? Not necessarily. I will discuss some other strange possibilities: low-mass planets made mostly from water, iron, carbon compounds, etc. I'll describe how these possibilities fit into our current picture of planet formation and suggest how we can recognize them with upcoming planet search tools.
 
 
 
01/23/2007
 
Victoria Meadows (University of Washington)

Planets Around Other Stars: Exploring Habitability and Spectral Signatures

The search for life outside our Solar System will be undertaken using remote-sensing techniques to understand the spectroscopic properties of extrasolar planets. To improve our ability to interpret what we might find, the Virtual Planetary Laboratory NAI Alumni team uses realistic stellar spectra and generalized planetary climate-chemistry models to explore the effect of different stellar energy distributions on the atmospheric photochemistry and resultant spectra of Earth-like planets. In this presentation I will review results to date on the effects on atmospheric photochemistry, planetary habitability and the detectability of biosignatures for planetary host stars of different spectral type and UV activity levels. I will also highlight new modeling results relevant to photosynthesis in extrasolar planet environments, and attempts to generate "false positive" signatures of atmospheric oxygen, using high incident stellar UV radiation and model planets with dense carbon dioxide atmospheres.
 
 
 

2006

 
11/14/2006
 
David Deamer

Self-Assembly Processes in the Prebiotic Environment

 Although the physical environment that fostered primitive cellular life is still largely unconstrained, we can be reasonably confident that liquid water was required, together with a source of organic compounds and energy to drive polymerization reactions. There must also have been a process by which the compounds were sufficiently concentrated to undergo physical and chemical interactions. Our laboratory is exploring self-assembly processes and polymerization reactions of organic compounds in natural geothermal environments and related laboratory simulations. We have found that RNA-like polymers can be synthesized non-enzymatically from ordered arrays of mononucleotides in lipid microenvironments. Chemical activation of the mononucleotides is not required. Instead, synthesis of phosphodiester bonds is driven by the chemical potential of fluctuating anhydrous and hydrated conditions, with heat providing activation energy during dehydration. In the final hydration step, the RNA is encapsulated within lipid vesicles. The reaction has been shown to occur not only in a laboratory setting, but also on mineral surfaces of a hydrothermal volcanic site on Mt. Lassen. We are now extending this approach to template-directed synthesis of RNA, in which lipid-assisted polymerization serves as a model of an early stage of evolution toward an RNA World.
 
 
 
10/24/2006
 
George Shaw

A (Not So) Brief History of Carbon on Earth

 
It is widely agreed that carbon first arrived on Earth in a reduced form, as found in almost all meteorites, and was abiotic in origin. For more than thirty years, the prevailing view has been that the carbon in Earth’s early atmosphere (and near surface environment) was virtually all in the form of carbon dioxide, the oxidized chemical state found in volcanic gases that are thought to be the source of atmospheric carbon compounds resulting from degassing of Earth’s interior. For about the same period of time there has also been broad agreement that a large fraction of the near-surface volatiles, including both water and carbon compounds, were degassed very early in Earth’s history, implying a carbon dioxide rich early atmosphere. This has been thought by many to be a suitable explanation of the necessary enhanced greenhouse effect required to compensate for the early faint sun. On the other hand there are several lines of evidence strongly at odds with this model for the early atmosphere:

1) Very early, Rubey pointed out the drastic geochemical and sedimentological consequences of a large CO2-rich atmosphere, including both severe weathering effects and consequent massive deposition of carbonate rocks, for which there is little or no evidence in the early Archean.

2) The delay in oxygenation of the atmosphere following the advent of oxygenic photosynthesis in cyanobacteria, as early as 2.8 BYBP (perhaps even earlier) is a long recognized (if often ignored) problem. Analysis of various sinks and nutrient constraints does not eliminate this problem.

3) The record of carbon isotopes in sediments points to a longstanding (at least since ca. 3.5 BYBP) balance between carbonate carbon and biogenic (fixed organic) carbon at a ratio of about 4 to 1. This implies substantial (and very early) fixation of large amounts of biogenic carbon and release of proportional amounts of free oxygen, which is inconsistent with geologic and isotopic evidence for an anoxic surface environment until ca. 2.1-2.3 BYBP.

These problems could be solved if one could identify a reservoir to hold the degassed carbon and release it into the biosphere on a geologic time scale. The lack of residual early Archean carbonate sediments (or metasediments) from such a hypothetical reservoir speaks against carbonate as the reservoir substance. The likelihood of early degassing precludes a deeper (e.g. upper mantle) reservoir. The only remaining choice is a reduced carbon reservoir at or near the surface. This reservoir cannot be atmospheric methane (or other gaseous hydrocarbon) because photochemical reactions rapidly remove such compounds from the atmosphere. An early ocean with a high concentration of photochemically (and electrically) produced complex organic compounds solves all of these problems, with the added attraction that it is a favorable environment for the emergence of life. The oxidation of subducted organic rich sediments during upper mantle magmagenesis slowly provides CO2 to the surface environment, on a time scale consistent with the time scale for oxygenation of the surface environment by photosynthetic cyanobacteria, with the record of carbon isotopes in sedimentary rocks, and with the record of carbonate sedimentation. An early reduced carbon reservoir at/near Earth’s surface follows directly from early degassing, under reducing conditions, of the original (and/or hydrogenated) meteoritic carbon compounds. The largely methane atmosphere so produced is short lived, but the photochemical products accumulate in the ocean and are continuously recycled into the atmosphere as methane by low temperature hydrothermal activity. This model provides a suitable source of the early (methane) enhanced greenhouse effect.

 
 
 
10/17/2006
 
Mario Livio

Cosmology and Life

I will examine recent findings in cosmology and their implications for the emergence of life in the universe and the ultimate fate of life. In particular, I will discuss: (i) The requirements for carbon-based life and their dependence on the values of physical constants, (ii) The inflationary model and its potential implications for the existence of an ensemble of universes, (iii) The nature of dark energy and its relation to life, (iv) The possibility of time-varying constants of nature, and (v) The question of the potential rarity of intelligent life.
 
 
 

2005

 
12/06/2005
 
Eric Agol (University of Washington)

The Future of Extrasolar Planet Searches

I will review the present state of our knowledge of the properties of planets orbiting other stars, I will discuss how these planets have been found, and I will outline the future prospects for finding yet more planets and even smaller planets. I will specifically focus on some novel techniques that are still currently being developed, but may yield detections of planets in the near future. I will describe how this year a graduate student and I have demonstrated for the first time the capability of detecting earth-mass planets about a sun-like star with a technique we developed last year.
 
(Recording Unavailable)
 
 
11/29/2005
 
Martin Fisk

Life in Igneous Rocks on Earth and Mars

Microbes are found in and near microtunnels in a variety of igneous rocks on Earth. Although the microtunnels have not been produced in laboratory cultures, all indications are that microbes made the tunnels. The tunnels provide long-lasting markers of life on Earth and if microbes ever lived on Mars, they would have left similar evidence in the igneous rocks there.
 
(Recording Unavailable)
 
 
11/22/2005
 
Donald Brownlee

Life in Igneous Rocks on Earth and Mars

On January 2, 2004, Stardust finally reached its target for a brief but daring encounter. The spacecraft flew within 236 km of the comet Wild 2 and survived the high speed impact of millions of dust particles and small rocks up to nearly half a centimeter across. With its tennis racket shaped collector extended, Stardust captured thousands of comet particles that will soon be returning to Earth on January 15, 2006.
 
(Recording Unavailable)
 
 

2004

 
12/07/2004
 
Maria Rivera

The Ring of Life Provides Evidence for a Genome Fusion Origin of Eukaryotes

The Tree of Life representing the connections among all organisms has become an icon of evolutionary biology. But recent analyses of completely sequenced genomes and the discovery that horizontal gene transfer (HGT) has significantly shaped microbial evolution have challenged the concept of the Tree of Life. We have determined the general outline of the tree using complete genome data from representative prokaryotes and eukaryotes and using a new genome analysis method that makes it possible to reconstruct ancient genome fusions and phylogenetic trees even in the presence of HGTOur analyses indicate that the eukaryotic genome resulted from a fusion of two diverse prokaryotic genomes, and therefore at the deepest levels linking prokaryotes and eukaryotes, the tree of life is actually a ring of life. One fusion partner branches from deep within an ancient photosynthetic group, and the other is related to the archaeal prokaryotes. The eubacterial organism is either a proteobacterium, or a member of a larger photosynthetic group that includes the Cyanobacteria and the Proteobacteria.
 
(Recording Unavailable)
 
 
11/16/2004
 
Penny Boston

Life Below and Life "Out There": The Role of Caves in Astrobiology

(Abstract Unavailable)
 
(Recording Unavailable)
 
 
11/09/2004
 
David Des Marais

The Mars Exploration Rover Mission

The rovers Spirit and Opportunity are robotic field geologists that investigate the crustal composition, environmental history, and potential habitability of Mars. The Gusev Crater and Terra Meridiani landing sites were selected to “follow the water” that might have shaped their landscapes and mineralogy. At Gusev Crater, the Spirit rover observed evidence of liquid water in fractures and cavities in rocks near the landing site, in salty horizons in the soil, and in extensively altered rocks in the Columbia Hills. At Meridiani Planum, Opportunity discovered sulfate-rich bedrock, sedimentary laminations, hematite concretions, and bedrock dissolution features that indicate the former presence of abundant liquid water. The MER rovers have shown that both sites had the potential to sustain life sometime in the past.
 
(Recording Unavailable)
 
 
11/02/2004
 
James Murray

The Suboxic Zone in the Black Sea

The Black Sea is a large permanent anoxic basin that has been considered an analog for the ancient earth’s ocean. This sea has an oxic surface layer over an anoxic (sulfide containing) deep layer. At the boundary there is a layer that is about 50 m thick with no oxygen or sulfide. In this layer there are many interesting intermediate redox reactions involving species of Fe, Mn and N.
 
(Recording Unavailable)
 
 
10/26/2004
 
Walter Harris

In the Rearview Mirror: Studying the Role of Comets in the Formation and Ongoing Evolution of a Planetary System

Comets are primordial objects that are the remnants of planetary formation in the solar system. From studies of their composition we are given insight into the conditions that prevailed in the proto-solar nebula, to the dynamical evolution of the planets as they formed, and possibly to characteristics of early terrestrial planet atmospheres. They are also important astrophysical laboratories for the study of plasma interactions and properties of gas and ions in the rarefied interplanetary medium. In this presentation I will discuss the origins of comets and their current reservoirs in the solar system, how they reach the inner solar system and how they are studied to determine both their structure and the characteristics of the neutral and ionized materials they produce. I will also describe our multifaceted program for the study of comets in our and other planetary systems that employs a combination of ground and space based observing tools.
 
(Recording Unavailable)
 
 

2003

 
12/09/2003
 
Steven Benner

Weird Life

The life that we know on Earth is fantastic, but is rapidly becoming quite familiar in its structure, from its physical form to its chemical details. But what about the life that we will encounter as we explore the galaxy? Will it be like in “Star Trek”, appearing like actors wearing protheses? Or will it be fundamentally different? Over the past five years, much new research allows us to place constraints on life that might lie out there. It might be weirder than we expect.
 
(Recording Unavailable)
 
 
11/18/2003
 
Peter Ward

Why There Were Dinosaurs; Why There Are Birds

New information on the levels of atmospheric oxygen through the Phanerozoic indicates that the end of the Permian and end of the Triassic were times of greatly lowered oxygen compared to the present day, equivalent to the oxygen content at current altitudes in excess of 12,000 feet. Here I propose that the combination of low oxygen and repeated short spikes in global temperature caused by methane induced atmospheric greenhouse conditions that were the primary causes of the P/T and T/J mass extinctions. These lowered oxygen levels, which according to the models persisted through the Triassic and into the early Jurassic (with minima at 250 and 200 Ma) may well have lead to the evolution of bone pneumatization found in modern birds and most lineages of saurischian dinosaurs examined to date. New physiological studies of this system in extant birds shows it to be far superior to the respiratory systems of lizards, amphibians, and mammals in surviving at high altitude (and thus lowered oxygen). It also appears that vertebrate lineages with this newly-evolved respiratory system had higher survival rates across the T/J mass extinction interval than did lineages with the air-sac system.
 
(Recording Unavailable)
 
 
10/14/2003
 
James Kasting

Methane Greenhouses and Anti-Greenhouses on the Early Earth

Methane was probably much more abundant in the low-O2 Archean/early Paleoproterozoic atmosphere, prior to 2.3 Ga, than it is today. CH4 concentrations of 1000 ppm or more are predicted once methanogenic bacteria had evolved. Greenhouse warming from this CH4 could have been a major factor in offsetting reduced solar luminosity at that time. However, if CH4 became more abundant than CO2, it would have polymerized to form hydrocarbon smog in the stratosphere. This, in turn, would have created an anti-greenhouse effect that cooled the surface. The rise of O2 at 2.3 Ga wiped out most of this methane and may have triggered the very deep (possibly global) Paleoproterozoic glaciations.
 
(Recording Unavailable)
 
 
05/27/2003
 
Robert Blankenship

The Transition from Anoxygenic to Oxygenic Photosynthesis and How It Changed the Earth

The buildup of oxygen in the Earth’s atmosphere that began about 2.2 BYA was one of the most important events in the history of the planet. While there is consensus that this increase in free oxygen was the result of oxygenic photosynthesis, very little is known about the evolutionary events that had to take place for this event to take place. Before oxygenic photosynthesis was invented there was a more primitive anoxygenic, or non-oxygen-evolving form of photosynthesis. This talk will bring together a variety of lines of evidence, including comparative biochemistry, structural biology and genomics to try to gain insights into how this transition took place. 
 
(Recording Unavailable)
 
 
05/20/2003
 
Roger Buick (University of Washington)

A Subsurface Biota in the Archean?

Though a large subsurface biota is thought to exist on Earth now, it is unclear whether this has always been so. The issue is, however, important because early in planetary history, subsurface environments might have been more habitable than surface sites and indeed might have formed refuges for life against the vagaries of meteoritic bombardment. It is even possible that if the earliest organisms were thermophilic chemolithotrophs, life might have originated in a subsurface hydrothermal setting. Here I critically examine the empirical evidence for the existence of a subsurface biota early in Earth’s history during the Archean era, concluding that there are strong but not totally compelling data supporting the occupation of subsurface habitats by the mid-Archean.
 
(Recording Unavailable)
 
 
04/29/2003
 
Tori Hoehler

Energetic Habitability: Boundary Conditions for Life-As-We-Know-It

(Abstract Unavailable)
 
(Recording Unavailable)
 
 
04/22/2003
 
Jack Farmer

Microbial Biosedimentology of Some Extreme Terrestrial Environments with Implications for the Exploration for Extraterrestrial Life

(Abstract Unavailable)
 
(Recording Unavailable)
 
 
04/15/2003
 
Geoff Garrison

Geochemical Seasonality in a Unique Aquatic Environment: Who Needs Oxygen, Anyway?

One of the pillars of astrobiology research is understanding how life can exist in modes other than what is typical on earth, and what kinds of chemical signals such unique life forms can produce. This talk will present the biogeochemical dynamics of a recently studied extremely productive closed pond on the leeward shore of Oahu, Hawaii. What makes this pond unique is that despite its high levels or organic productivity (>470 mg C m-2 d-1), the waters of the pond remain suboxic to anoxic, even at the very surface, during most of the year. A system with such large chemical disequilibria provides an easily accessible natural laboratory for the study of unique microbial communities. It’s also a short drive from the best Mai Tais in Hawaii.
 
(Recording Unavailable)