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Project Reports

• RPL and Expedition 357: Serpentinization and Life at the Atlantis Massif

  Circulating hydrothermal fluids associated with mid-ocean ridges represent some of the most prominent examples of the intersection between chemical energy and the biosphere. The Lost City Hydrothermal Field, which sits atop the Atlantis Massif near the Mid Atlantic Ridge hosts a microbial ecosystem which feeds off the products of serpentinization. IODP Expedition 357, which sailed in Fall 2015, obtained rock cores and fluids from the Atlantis Massif, which are being used for the coordinated investigation of serpentinization processes and life. Lost City is known to sustain abiogenic organosynthesis reactions and as such has been suggested to be an analogue to prebiotic early Earth environments and potential extraterrestrial habitats.

  ROADMAP OBJECTIVES: 3.1 3.4 5.1 5.2 5.3 7.2

• Field Activities at the Coast Range Ophiolite Microbial Observatory (CROMO)

  CROMO provides ongoing excellent exposure to samples of ophiolite-hosted serpentinites and associated rocks, access to monitoring wells important for observing serpentinization-related groundwater flow regimes, and serves as a community-building platform that fosters new scientific collaboration. CROMO has served as a test-bed for refining new experimental approaches, and progressing from basic observations to more complex, multi-disciplinary science.

  Within the past year, studies at CROMO have focused on the subsurface hydrogeochemical dynamics, by monitoring groundwater hydrology, measuring the concentrations and composition dissolved iron, sulfur, dissolved inorganic carbon, major inorganic anions and cations, dissolved hydrogen, carbon monoxide and methane gases, and organic compounds, in addition to time-series analyses.

  CROMO datasets are being incorporated into an exploratory database project aimed at addressing NASA’s public data requirements. Once developed, this database will help to address data sharing plans for collaborators and serve as a valuable tool for CROMO data management across collaborating labs.

  In 2015, project members Dawn Cardace, Masako Tominaga, Michael Kubo, Lauren Seyler, Mary Sabuda, Abigail Johnson, Ken Wilkinson, & Cameron Hearne participated in a field trip to CROMO from August 21-27, to continue seasonal bio/geo/chemical monitoring of the wells, as well as assessing the site for future geophysical measurements.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Deciphering the Mineralogy and Geophysical Properties of Serpentinized Rocks

  The transformation of mineral phases during water-rock interaction provides critical energy sources for life yet the reaction processes under low temperature conditions are enigmatic. Thus a key goal of the RPL NAI is to decipher the geochemical reaction path history recorded in rocks that have interacted with water at low temperatures. To that end, we are developing and optimizing analytical procedures for quantifying mineralogy, Fe oxidation state, and rock magnetism at the microscale. To date, we are applying an integrated suite of microsopic and spectroscopic techniques to mafic and ultramafic rocks that have undergone low temperature alteration in two ophiolite systems — surface and subsurface serpentinites from Oman and drill core material from the California Coast Range Microbial Observatory. The resulting integration of mineralogical and chemical images is critical in efforts to unravel the sequence of water/rock reactions. In future years, our approaches will be applied to a diversity of rocks to be recovered by drilling at sites undergoing active, low temperature reaction, such as the Atlantis Massif and the Oman ophiolite, as well as samples that will be generated from laboratory-based water/rock reaction experiments.

  ROADMAP OBJECTIVES: 7.1

• Insights Into Geochemical and Biological Processes in Serpentinizing Systems From Hyperalkaline Seeps in Oman

  Rock-powered life makes its living from reactions between rocks and water as part of the overall processes of rock weathering. There can be energy available because rocks from deep in the Earth are moved by tectonic forces into regions populated by microbes faster than chemical weathering processes alone can act. Under the right conditions, energy left behind can be consumed by microbial communities, and resulting biogeochemical reactions expedite overall weathering processes. In many cases, these energy sources and the communities they support are independent of sunlight. Instead, their energy and nutrient requirements are met by a combination of slow tectonic and rapid fluid mixing processes. One particularly dramatic example of how the combination of these processes support microbial communities is found in an area of Oman called the Samail ophiolite. Owing to unusual geologic proceses, tectonic forces moved rocks normally in the Earth’s mantle to the surface of the continent on the Arabian peninsula about 65 million years ago. Ever since, the introduction of mantle rocks into the surface hydrosphere has been a source of energy tapped by microbes. At present, in the arid climate of Oman, small amounts of annual precipitation infiltrate these rocks, react, and reappear at springs. Owing to the unusual rock compositions, these springs have remarkably unusual compositions. Not only does the pH go to extremely basic values, nearly reaching 12, but the solutions are so reduced that they can bubble with escaping hydrogen and methane. Although these springs are not hot, they can look like they are boiling in places with lots of escaping gas.

  ROADMAP OBJECTIVES: 5.2 5.3 6.1

• Physiology of Microbial Populations From W/R Hosted Ecosystems

  Microbial communities supported by chemical energy (chemotrophic communties) released through water / rock interactions are widespread in contemporary Earth environments, including the subsurface where light is excluded and in surface environments where physical or chemical conditions preclude photosynthetic metabolisms. Chemotrophic microorganisms are key targets of astrobiological investigation due to the strong likelihood that they predate photosynthetic metabolisms and because they can be physiologically tested to define the habitable limits for life on Earth, including those associated with extremes of temperature, pH, salinity, and energy availability. Research by RPL scientists is focused on identifying and characterizing the physiological strategies or mechanisms that allow life to persist under extreme conditions at the habitable limits. By combining this information with phylogenetic approaches, we aim to determine how and when these mechanisms evolved and what role they played in the diversification of early life. As such, this research effort is highly interdisciplinary and employs both traditional (e.g., activity assays, cultivation) and contemporary (genomics, transcriptomics, metabolomics) microbiological approaches in combination with geochemical approaches. In addition, RPL investigators are studying the evolution of these communities to hone in on the nature of key physiological processes (e.g., central carbon metabolism, nitrogen metabolism, and iron-sulfur metabolism) in chemotrophs prior to the onset of photosynthetic metabolisms. Field-based RPL investigations of microbial physiology in water/rock ecosystems to date have focused on populations inhabiting subglacial environments (cold-adaptation), hot springs (adaptation to acidity, high temperature), and subsurface peridotite environments (adapation to energy stress, nutrient stress, alkalinity).

  ROADMAP OBJECTIVES: 3.1 3.2 3.3 4.1 5.1 5.2 5.3

• Advances in Gene Sequencing From Low-Biomass Water-Rock Hosted Ecosystems

  One of the approaches our team is taking to explore rock-powered life is to study microorganisms hosted within rocks that are undergoing potentially life-supporting reactions with water. The chemistry of the rock microenvironments shapes the abundance, diversity and distribution of microbial life. In turn, that microbial life locally affects the in-situ geochemistry. This project is currently focusing on the successful extraction and sequencing of the exceedingly small amounts of DNA that accumulates within rocks, in order to successfully detect and characterize the rock-hosted life. Ultimately our improved approaches will support the application of next-generation DNA sequencing technology in the study of natural microbial ecosystems that are key for understanding the mechanisms of rock-powered life.

  ROADMAP OBJECTIVES: 3.2 4.1 5.1 5.2 5.3 6.1 7.2

• High Temperature W/R Hosted Microbial Ecosystems in Yellowstone

  Geochemical data indicate that life on early Earth was dependent on chemical forms of energy. This attribute, when coupled with phylogenetic data indicating that early evolving forms of life were thermophilic, lead many astrobiologists to believe that life evolved in a high temperature environment and was dependent on chemical forms of energy to sustain its metabolism.

  Hydrothermal environments with temperatures >70ᵒC exclude life dependent on light energy, leaving only those life forms that can sustain themselves using chemical energy. The >14,000 hot springs in Yellowstone National Park therefore provide a unique field-based early Earth analog environment to examine the processes that sustain life dependent on chemical energy and to investigate the metabolic processes that sustain this life. Moreover, the chemical and physical variation present in these environments affords the opportunity to examine how this variation drove the diversification of life in these early Earth analog environments. RPL investigations in hot spring environments in Yellowstone in 2015 centered on answering questions related to the array of energy and carbon sources available to chemosynthetic life, the preferred carbon sources supporting this life, and the role of hydrogen transformation in the metabolisms of these organisms. By answering these interrelated questions, we will provide a framework by which we can use to begin to understand the processes that most likely sustained microbial life on the early Earth. Since it is possible, if not likely, that such processes would also sustain early life on other planetary bodies, this research has the potential to guide the search for life in non-Earth environments.

  ROADMAP OBJECTIVES: 3.2 3.3 4.1 5.2 5.3 6.1

• Modeling Habitable Environments Generated by Water/rock Reactions

  This project within the RPL NAI seeks to develop a framework for predicting biological potential (for example, volumetric biomass abundance) as a function of enviromental variables such as rock and fluid composition, water-to-rock ratio, and temperature. Building on the prediction that energy availability will be a key limitation in subsurface systems, we evaluating how variabliity in these environmental factors changes the potential to generate energy through particular metabolisms, and how that potential compares to the corresponding energetic demands of life within a particular set of physicochemcial conditions. We inform and ground truth this approach by comparing the landscape of energy availability in natural systems, such as the CROMO system, to the distribution of microorganisms observed there.

  ROADMAP OBJECTIVES: 2.1 2.2

• Variable Generation of H2, Formate, and Critical Electron-Donors During Water/rock Reaction

  The chemosynthetic microbial communities that inhabit peridotite-hosted springs and hydrothermal systems are supported by molecular hydrogen (H₂), formate, and other electron donors that are generated by subsurface fluid-rock interactions during serpentinization. The objective of this project is to understand the sources, abundances, and diversity of critical electron donors produced during serpentinization, and how they vary as a function of environmental parameters such as temperature, rock composition, and reaction time. Our primary approach is to examine fluid-rock interactions through laboratory experiments, which will supply inputs to geochemical models being conducted by other members of the RPL team and provide a basis for interpreting the distribution and diversity of microbial communities in natural systems. During this first year, experiments were initiated to study fluid-rock interactions in low- to moderate-temperature environments, with initial results expected early in 2016. Also this year, we continued development and construction of a new type of reaction vessel optimized for low temperature (25-100 °C) water-rock reaction experiments.

  ROADMAP OBJECTIVES: None Selected

• Rock Powered Life: Education and Communications

  The central theme of the Rock Powered Life research effort is to define how, where and when water/rock interactions release energy and how this energy is harvested to support microbial communities. These studies are of fundamental importance for improving understanding of how microbial life was supported on early Earth. Moreover, since similar reactions can be expected on any rocky planet with liquid water, these studies provide new constraints for predicting the distribution of life on other planetary bodies.

  The focus of our team – rock-hosted microbial ecosystems that are dependent on chemical rather than light energy – provides novel avenues to engage the next generation of astrobiologists and to disseminate knowledge to the broader public. Here we describe current and ongoing efforts by members of Rock Powered Life that are aimed at improving engagement and training in astrobiology. Of particular relevance are efforts to provide opportunities to provide underrepresented high school and undergraduate students hands on training opportnities in astrobiology-focused studies. We also describe advancements in Rock Powered Life’s digital-based information sharing technologies. Through these integrated team efforts we aim to attract and train future generations of astrobiologists and to provide greater access to the current knowledge base with which to understand the potential for life elsewhere on other planetary bodies.

  ROADMAP OBJECTIVES: 3.2 4.1 4.2 5.1 5.2 5.3 6.1 6.2

• Subglacial Environments as Water‐Rock Hosted Microbial Ecosystems

  Glaciers, ice sheets and ice caps cover ~11% of the earth’s surface, and likely covered up to 100% during Neoproterozoic glaciations. The beds of these ice masses can have significant sectors at the pressure melting point. The resulting water lubricates ice sliding and accelerates erosion, provides habitat for subglacial microbial ecosystems, and may have acted as refugia during past global glaciations on Earth. Such environments may also act as habitats for life on other planetary bodies.

  Grinding of bedrock by glaciers exposes fresh mineral surfaces capable of sustaining microbial metabolism. The foci of RPL investigations on subglacial environments are categorized into two key areas of relevance to habitability studies: i) determine the extent to which minerals support chemotrophic metabolism and the production of biosignatures (e.g., weathering products), and ii) quantifying the influence of water-rock interactions in supplying substrates to support energy metabolism. Through these interdisciplinary and collaborative studies, we aim to characterize the active microbial processes in subglacial environments and to define the sources of energy that sustains this microbial life.

  ROADMAP OBJECTIVES: 2.1 5.1 5.2 5.3 6.1 6.2 7.2

• Subsurface Serpentinization Processes and In-Situ Microbial Life in Oman

  The Rock-Powered Life team has initiated several field-based efforts in Oman focused on characterizing the geochemistry and microbial community structure and activity within massive exposures of peridotites undergoing low-temperature serpentinization. In this project, we are using deep wells drilled hundreds of meters into peridotite catchments to access waters stored in the deep subsurface, and to capture the mineralogical and biological processes that give rise to hyperalkaline fluids rich in dissolved H₂ and CH₄. In particular we extract biomass from the fluids for genetic sequencing in order to identify the types of life that can live within the extreme conditions of low energy and carbon availability, and to infer the metabolisms that sustain in-situ life activity. These analyses are paired with mineralogical analyses of the subsurface rocks and isotopic analyses of the dissolved gases in order to quantify the water/rock reactions occurring in the modern system that give rise to energy transfer from the rocks to living ecosystems.

  ROADMAP OBJECTIVES: 3.1 4.1 5.3 7.2