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.
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.
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.
Cecilia Bitz (University of Washington)
Modeling the Climate of Exoplanets with GCMs
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Kyle Costa (University of Washington)
Influence of Precipitation on the Movement of Salts Through Hyper-Arid Desert Soil
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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.
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.
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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."
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.
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.
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.
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.
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.
Robert Tyler (NASA Goddard Space Flight Center)
The Importance of Tidal Flow in Maintaining an Abundance of Liquid Oceans in the Universe
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.