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Project Reports

• Stoichiometry of Life – Task 2c – Field Studies – Other

  We continued analyses of organic matter in samples of porewaters from a deep ocean hydrothermal mound; concluded a study on element acquisition by biological soil crusts, and initiated a new study that may shed light on a recent hypothesis that floating pumice may have been a site for the origin of life. In this new study, the eruption of the Puyehue / Cordon Caulle volcano on 4 June 2011 near Bariloche, Argentina, provided a unique opportunity to investigate floating pumice as a unique habitat for microbial life. To assess this, we sampled floating pumice from various regional lakes to assess the make-up of the associated microbial communities using genomic techniques and to evaluate the use of key elements (nitrogen, phosphorus) by these microbes using chemical and isotopic methods.

  ROADMAP OBJECTIVES: 4.1 5.2 5.3 6.1

• Astrophysical Controls on the Elements of Life, Task 3: Model the Injection of Supernova Material Into Star-Forming Molecular Clouds

  The goal of this task is to see if material ejected from a star that has exploded as a supernova can make its way into the gas as it is forming new solar systems. It has been expected that this material, because it is moving so fast (> 2000 km/s) when it hits the cold, dense molecular cloud in which stars are forming, would shock, heat up, and then “bounce” off of the cloud boundary. Our numerical modeling using state-of-the-art numerical codes and thousands of computers at the Arizona Center for Advanced Computing, shows that the gas can in fact cool quickly enough to penetrate into the molecular cloud. Stars can be contaminated with supernova material just as they are forming, at contamination levels consistent with isotopic and chemical evidence from meteorites.

  ROADMAP OBJECTIVES: 1.1 3.1

• Astrophysical Controls on the Elements of Life, Task 1: High-Precision Isotopic Studies of Meteorites

  The initial Solar System abundances of the short-lived radionuclides (SLRs) ²⁶Al (half life ~0.73 Ma) and ⁶⁰Fe (half life ~2.6 Ma) are important to constrain since, if present in sufficient abundance, these SLRs served as heat sources for dehydration and differentiation processes on planetary bodies. The implications for this work include the astrophysical environment in which the Sun formed, and the abundance of water on the terrestrial planets.

  ROADMAP OBJECTIVES: 1.1 3.1

• Stoichiometry of Life, Task 3a: Ancient Records – Geologic

  Fossil and chemical fingerprints of animal life first appear in the geologic record around 600 million years ago. The four billion years of Earth history before this milestone were marked by dramatic changes that we take for granted today but that set the stage for our existence. Among the key events recorded in very old rocks is the first rise of oxygen in the atmosphere and ocean about 2.5 billion years ago following two billion years of a virtually oxygen-free world. And this evolving chemical state was the backdrop against which photosynthesis first evolved; simple, single-celled organisms appeared and diversified; and the first eukaryotic life evolved as a forerunner to the complex animals that would follow one-to-two billion years later. Our work is exploring the evolving compositions of the early atmosphere and ocean and their cause-and-effect relationships with the evolution of life—spanning the middle 50% of Earth history from the first production of oxygen via photosynthesis to the first appearance of animals. Darwin would have been pleased to know that early rocks tell us a convincingly strong: long before the animals, the oceans were teeming with life and that this life set the stage, in so many ways, for the later evolution of animals. Our sophisticated geochemical tracers are changing our view of the early environmental conditions that facilitated, and just as often throttled, the rise of life and the ways life can passively and intentionally modify its own environment—not unlike the lessons we are learning about our relationship with the changing ocean, atmosphere, and climate today.

  ROADMAP OBJECTIVES: 4.1 4.2

• Habitability of Water-Rich Environments, Task 4: Evaluate the Habitability of Ancient Aqueous Solutions on Mars

  As a member of the MSL Science team, Prof. Farmer actively supported surface operations of the Mars Science Laboratory rover Curiosity at JPL throughout the first 90 days of the mission (ongoing). During this time he offered a videocon-based upper division/graduate level course from JPL each week. (GLG 455/598: Advanced Field Geology – The MSL Mission Live from Mars). 
Prof. Farmer also completed a Raman-based study of sulfate evaporites to assess the biosignature preservation potential of this important Mars analog rock type. The work was done in collaboration with J.W. Schopf at UCLA and was published last Spring in the journal, Astrobiology. With Dr. Steve Ruff (Research Assoc., ASU), Prof. Farmer continued terrestrial analog studies in Yellowstone National Park and at Mauna Loa, Hawaii, to understand sulfate- and silica-precipitating hydrothermal systems documented at Home Plate in the Columbia Hills of Gusev Crater, Mars in 2011.

  Prof. Zolotov developed models to predict the clay mineralogy of Mawrth Vallis, a potential future landing site for Mars astrobiology. His work suggested that this region of Mars has experienced extensive acidic weathering under a low rock:water ratio. His work also provided insights into the nature of potentially habitable subsurface environments at Mawrth Vallis.

  ROADMAP OBJECTIVES: 2.1

• Habitability of Water-Rich Environments, Task 5: Evaluate the Habitability of Small Icy Satellites and Minor Planets

  The goal of this project is to determine the internal structure of small icy bodies, especially the objects like Pluto and its moon Charon, which are Kuiper Belt Objects (KBOs). The possibility exists that these icy bodies may contain liquid water at great depths, despite their frigid surface temperatures and small sizes, because radioactivities heat them and their ices might contain antifreezes like ammonia. We are also evaluating the chemical composition of aqueous solutions which could have formed shortly after formation of asteroids and moons of giant planets. Another of our tasks is to estimate chemical composition of methane-rich liquids that are present at the surface of Titan at extremely low temperatures.

  ROADMAP OBJECTIVES: 2.2

• Astrophysical Controls on the Elements of Life, Task 6: Determine Which Elemental or Isotopic Ratios Correlate With Key Elements

  Abundances of both common and trace elements can have substantial effects on the habitability of stellar systems. We study the formation and composition of structures in supernova explosions that deliver bioessential elements to material that will form new stars and planets. We use the abundance of the element europium to estimate the abundances of uranium and thorium in nearby stellar systems and their effects on the thermal evolution of extrasolar planets. The relative abundances of common elements vary substantially among nearby stars, and we find that the impact of this on a star’s evolution can change the amount of time its planets are habitable by billions of years.

  ROADMAP OBJECTIVES: 1.1 3.1

• Astrophysical Controls on the Elements of Life, Task 2: Model the Chemical and Dynamical Evolution of Massive Stars

  Stars create the chemical elements heavier than hydrogen and helium, with the majority arising from the lives and violent deaths of massive stars in supernova explosions. The starting chemical composition of stars also affects their evolution and that of their associated planets. We have performed computational simulations for a large range of stellar masses to provide predictions for important stellar characteristics (i. e. brightness, temperature, stellar winds, composition) over the stars’ lifetimes and made the data available to the public. We have also simulated the explosions of massive stars to predict the chemical abundances of material ejected from the dying stars and how that material is distributed in the surrounding universe. As a complement, we are finding the chemical abundances of hundreds of nearby, potentially habitable stars and modeling how the habitable zones and planets of stars with different abundances evolve.

  ROADMAP OBJECTIVES: 1.1 3.1

• Astrophysical Controls on the Elements of Life, Task 4: Model the Injection of Supernova Material Into Protoplanetary Disks

  The goal of this project is to determine whether supernova material could be injected into a protoplanetary disk, the disk of gas and dust from which planets form. A secondary issue is whether these materials would be mixed within the disk efficiently, and whether such an injection into our own protoplanetary disk can explain the isotopic evidence from meteorites that the solar system contained short-lived radionuclides like ²⁶Al.

  ROADMAP OBJECTIVES: 1.1 3.1

• Astrophysical Controls on the Elements of Life, Task 5: Model the Variability of Elemental Ratios Within Clusters

  This project aims to better understand the self-enrichment that goes on in star-forming molecular clouds as stars near the end of their lives and deposit heavy elements into the surrounding medium, where other stars are still in the midst of forming. Through detailed hydrodynamic simulations we are studying the mixing of heavy elements and its relation to variable abundance ratios in present-day clusters, as well as the transition from pristine to enriched star formation in the early universe.

  ROADMAP OBJECTIVES: 1.1 3.1

• Stoichiometry of Life, Task 2b: Field Studies – Cuatro Cienegas

  Cuatro Cienegas is a unique biological preserve in México (state of Coahuila) in which there is striking microbial diversity, potentially related to extreme scarcity of phosphorus. We aim to understand this relationship via field sampling of biological and chemical characteristics and a series of enclosure and whole-pond fertilization experiments. These studies help in identifying the element signatures that microbes develop when key nutrient elements are scarce. Furthermore, the chemical and physical environments of the desert aquatic habitats at Cuatro Cienegas are analogous to those that may have existed on Mars during times in its past when it was losing its own surface water. Thus, these data may help in interpreting information about element signatures obtained from the Curiosity rover as it explores Gale Crater.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2

• Habitability of Water-Rich Environments, Task 1: Improve and Test Codes to Model Water-Rock Interactions

  The new computer codes could be used to calculate changes in phase composition during freezing or melting in cold icy environments on Mars, large water-bearing asteroids, icy moons of giant planets, comets, and other trans-neptunian objects. Another model will allow us to calculate composition of liquid hydrocarbons on the surface of Titan.

  ROADMAP OBJECTIVES: 2.1 2.2

• Stoichiometry of Life – Task 4 – Biogeochemical Impacts on Planetary Atmospheres

  Oxygenation of Earth’s early atmosphere must have involved an efficient mode of carbon burial. In the modern ocean, carbon export of primary production is dominated by fecal pellets and aggregates produced by the animal grazer community. But during most of Earth’s history the oceans were dominated by unicellular, bacteria-like organisms (prokaryotes) causing a substantially altered biogeochemistry. In this task we experiment with the marine cyanobacterium Synechococcus sp. as a model organism and test its aggregation and sinking speed as a function of nutrient (nitrogen, phosphorus, iron) limitation. We have found so far that these minute cyanobacteria form aggregates that can sink gravitationally in the water column, and we are currently experimenting with minerals that might have been present in the Proterozoic ocean to see if those can accelerate sinking.

  ROADMAP OBJECTIVES: None Selected

• Habitability of Water-Rich Environments, Task 2: Model the Dynamics of Icy Mantles

  One of Jupiter’s moons, Europa, is one of the few places in the solar system in which the physical and chemical conditions may be suitable for sustaining life. Europa is composed on an outer H₂O layer, comprised of rigid ice overlying a liquid water ocean. It is this liquid water ocean which has been hypothesized as having the ingredients necessary for life, but it is shielded from our observation by the thick ice layer. However, under certain conditions, the ice layer is expected to undergo convection, possibly transporting chemicals from the liquid ocean to the surface, where we may be able to detect them. We perform computer modeling of ice/ocean convection to investigate how ocean material is carried up through the ice layer and whether it is expected to reach Europa’s surface. This work provides guidance for future missions which may probe the chemistry of the ice surface.

  ROADMAP OBJECTIVES: 1.1 2.2

• Astrophysical Controls on the Elements of Life, Task 7: Update Catalog of Elemental Ratios in Nearby Stars

  We have created the first complete database of bioessential elements for the stars closest to the Sun, including those hosting exoplanets.

  ROADMAP OBJECTIVES: 1.1 7.2

• Habitability of Water-Rich Environments, Task 3: Evaluate the Habitability of Europa’s Subsurface Ocean

  Europa is of keen interest to astrobiology and planetary geology due to its indications of a sub-surface ocean. Understanding of Europa’s oceanic composition and pH is important to evaluate habitability of the icy moon. Knowledge of the global distribution and timing of Europan geologic units is a key step for understanding the history of the satellite and for identifying areas of recent activity. We are evaluating the habitability of a subsurface ocean of Europa through evaluation of chemical composition and salinity of oceanic water. We use numerical approaches to model interaction of possible rocks on Europa with water formed through melting of ices. In addition, we use chemical and mineralogical signs of water-rock interactions in carbonaceous chondrites as a proxy for aqueous processes on Europa.

  ROADMAP OBJECTIVES: 1.1 2.2

• Stoichiometry of Life – Task 1 – Laboratory Studies in Biological Stoichiometry

  This project component involves a diverse set of studies of various microorganisms with which we are trying to better understand how living things use chemical elements (nitrogen, phosphorus, iron, etc) and how they cope, in a physiological sense, with shortages of such elements. For example, how does the “elemental recipe of life” change when an organism is starved for phosphorus or nitrogen or iron? Is this change similar for diverse species of microorganisms? Furthermore, how does an organism shift its patterns of gene expression when it is starved by various nutrients? This will help in interpreting studies of gene expression in natural environments, including extreme environments relevant to astrobiology.

  ROADMAP OBJECTIVES: 5.2 5.3 6.1 6.2

• Stoichiometry of Life, Task 2a: Field Studies – Yellowstone National Park

  Our stoichiometry studies are determining the relationships between the elemental compositions of organisms and the elemental compositions of their environments. We experimentally determine how changes in element availability (N, P, Fe) affect the community structure in hot spring ecosystems. We also use stable isotopes (¹⁵N and ¹³C) to trace which metabolisms actively utilize N and C and where in cells these elements are used. Recently, our team has shown for the first time that nitrogen (N₂) fixation can occur at temperatures >85oC (Loiacono et al. 2012). We are also developing robust environmental sensors for hot springs that reveal chemical and thermal gradients at scales similar to the observed spatial distributions in hot spring microbial communities.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.2

• Stoichiometry of Life, Task 3b: Ancient Records – Genomic

  The goal of Task 3b is to bring the enormous and ever-increasing repository of genomic data, both from single organisms and natural environments, to bear on understanding the history of life on Earth. Team members bring together innovative, integrative methods for understanding the interaction and feedback between life and environment, in particular how nutrient and energy limitations shape evolution. These efforts are focused not only on ancient records, but also are playing an important role in understanding how life and environment co-evolve on the modern Earth.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3