2011 Annual Science Report
Arizona State University Reporting | SEP 2010 – AUG 2011
The “Follow the Elements” NAI Team at ASU carries out research, education and outreach activities centered on the chemical elements of life. Our activities are motivated by a simple observation: that life-as-we-know-it uses a non-random selection of the chemical elements. This observation prompts many questions:
- What are the rules that govern the selection of these “bioessential” elements?
- How might these elements differ in extreme environments on Earth or beyond?
- How common are the bioessential elements in the extraterrestrial environments that might harbor life?
- How are the distributions of these elements in the cosmos shaped by astrophysical processes?
The answers to these questions will shape the future exploration for life on other worlds. We seek to answer these questions through laboratory, field and computational research, and use them as the basis for much of our education and outreach. To this end, the project is organized around three major research themes: The Stoichiometry of Life; The Habitability of Water-Rich Environments; and Astrophysical Controls on the Elements of Life. We pursue each theme by way of a number of focused research tasks.
During Year 3 of our program, the Astrobiology Program at Arizona State University continued to advance most of the major research tasks described in our CAN5 proposal, and other new projects. These efforts resulted in at least 75 publications that appeared in print, were submitted or reached an advanced state of preparation or were presented at international conferences during the reporting period. These included several publications in high-profile journals. Collectively, this ongoing research advanced our goal of integrating life science, geoscience, planetary science and astrophysics to understand how the distribution of chemical elements shapes the distribution of life in space and time, and to guide the search for life beyond Earth. This work is comprehensively described in the main report. Key outcomes are highlighted here.
1. The Stoichiometry of Life
This theme includes several tasks aimed at elucidating relationships between the availability of bioessential elements and prokaryotic ecosystems. These tasks involved: experimental studies (Task 1); field studies and associated laboratory analyses at Yellowstone National Park, Cuatro Cienegas, Mexico and other sites (Tasks 2a, b, c and d respectively); evolutionary studies in the geologic and genomic records (Tasks 3a and 3b, respectively); and a coupled modeling-experimental project to understand the connections between biogeochemical cycles of carbon, oxygen and bioessential nutrient elements in prokaryote-dominated oceans (Task 4).
Task 1 projects continued to advance on multiple fronts, and melded somewhat with our Task 2 projects as samples gathered in the field were intensively studied in the laboratory. Notable outcomes from Tasks 1 and 2 included:
- Advances in our ability to separate cells from non-biological materials collected from the field. This seemingly simple but surprisingly difficult undertaking is central to our goal of characterizing the stoichiometry of extremophiles in natural settings.
- Maturation of a suite of projects centered on understanding molybdenum acquisition in natural systems, spearheaded by ASU Ph.D. graduate Jennifer Glass (who began a NASA Postdoctoral Fellowship at Caltech at the end of the reporting period). This trace element is key to the biological nitrogen cycle.
- Submission and publication of multiple papers tied to the genomics and biological stoichiometry of the Cuatro Cienegas field site (a special issue of Astrobiology on this site is planned for early 2012), led by ASU Co-I Jim Elser and collaborator Valeria Souza (National Autonomous University of Mexico). The work was the basis for a Nature News article on efforts to preserve this unique ecosystem.
- Advances in our work reconstructing nitrogen and carbon metabolism in hotsprings at Yellowstone National Park. These efforts use 15N and 13C tracers to follow these elements. 15N efforts, overseen by ASU collaborator Hilairy Hartnett, benefited from ASU’s installation of a NanoSIMS instrument for in situ isotopic analyses. 13C efforts, led by ASU postdoc Amisha Poret-Peterson, revealed the first direct evidence for methylotrophy in this hotspring environment.
In Task 3, our central effort to understand the coupled environment and ecology of a 1.5 billion year old ocean basin advanced substantially, as a suite of inorganic geochemical data were obtained that complement organic biomarker data obtained in Year 2, by postdoc Amy Kelly, who relocated from UC Riverside to ASU during the project year. Also notable were a series of high profile papers, largely generated by the laboratory of UC Riverside Co-I Tim Lyons, which have redefined our understanding of ocean chemistry during this era. Recently thought to be dominated by sulfidic deep seas, we are now concluding that such environments, while more common than today, were less common than had been hypothesized. Instead, the bulk deep sea was characterized by low O2 and elevated iron abundances – so-called “ferruginous” conditions.
The most visible research highlight during the reporting period was the publication in Science (Express) in late 2010 of Wolfe-Simon et al.’s paper on arsenic substitution for phosphorus in biomolecules of the bacterium GFAJ-1 isolated from Mono Lake, CA. Lead author postdoc Felisa Wolfe-Simon developed the hypothesis that the toxic element arsenic could replace phosphorus in biological molecules, described in a paper published in 2009 with Ariel Anbar and Paul Davies of the ASU NAI Team, during a postdoctoral fellowship at ASU. The experimental and field work described in the 2010 Science paper were carried out in Ron Oremland’s laboratory at the USGS – Menlo Park, with some key inorganic elemental analyses done in Anbar’s lab. The hypothesis is provocative because all life as we know it requires the elements C, H, O, N, S and P, in specific ratios. If one of these elements could be replaced by another element in its key biological roles, even in part, it would profoundly modify our understanding of basic biology.
This work understandably generated intense interest, excitement and controversy in the scientific community and in the general public, with much coverage in major media and in the blogosphere. The scientific debate revolved around two broad themes: (a) Is the hypothesis of arsenic substitution plausible, a priori? and (b) Were the presented data sufficient to support the claim? These themes were the basis of an extensive suite of technical comments and responses published alongside the print version of the paper in Science in mid-2011. The coverage in the blogosphere was itself a watershed moment in the evolution of science journalism and the presentation of scientific results, highlighting the very different pace of traditional and online reporting and publication, raising questions about the relative merits of the traditional peer review process vs. more “open” forms of science and about the practices that should be followed in publicizing novel scientific findings in the internet era. The matter remains controversial and unresolved as of the time of this report, with several groups working to reproduce or extend the original findings.
2. The Habitability of Water-Rich Environments
This goal of this theme is to improve our ability to infer the availability of bioessential elements in aqueous environments on Mars, in the outer Solar System, and on water-rich exoplanets. It includes tasks involving: Improving computational codes to model water-rock interactions (Task 1); application of modern geodynamics codes to ice dynamics on Europa and other icy bodies (Task 2); integration of these and other computational models with observational data to better assess the habitability Europa (Task 3), Mars (Task 4), other small icy bodies (Task 5), and postulated extrasolar “waterworlds” (Task 6).
Work along these tasks advanced efficiently. Notable highlights included the maturation of ASU Co-I Mikhail Zolotov’s most recent suite of geochemical computational codes and of ASU collaborator Allen McNamara’s geophysical numerical simulations of mass transfer across the boundary between Europa’s surface ice and liquid water ocean, now spearheaded by ASU graduate student Divya Allu Peddinti. ASU Co-I Steven Desch continued his development of thermal evolution models of small icy bodies, which are characterized by the prediction that such bodies are only partially differentiated. While on sabbatical at NAI member University of Hawaii, he initiated a collaboration with UH PI Karen Meech that has led to an observational campaign to test the hypothesis of partial differentiation.
However, perhaps the most notable development in this theme, not captured in our task reports, was the selection of OSIRIS-REX as the next New Frontiers mission. This mission will return samples from a carbonaceous asteroid, providing novel insights into the origin of organics and volatiles on the Earth and other planets. This mission is led by the University of Arizona, where Co-I Dante Lauretta is the Deputy PI (just after the reporting period Lauretta was elevated to PI due to the untimely passing of PI Michael Drake). ASU collaborator Phil Christiansen will lead a team to build a thermal emission spectrometer for this mission, while ASU Co-I Mini Wadhwa will play a leading role in planning for analyses of returned samples. ASU Collaborator Sandra Pizarello, ASU graduate student Adam Monroe and UA graduate student Devin Schrader are working with Lauretta on meteorite studies preparatory for this mission.
3. Astrophysical Controls on the Elements of Life
This theme aims to elucidate the influence of supernovae and other nucleosynthetic processes on the formation of solar systems, their composition and evolution. The theme includes tasks involving: High-precision isotopic studies of meteorites to quantify the timescales of the injection of supernova-derived materials (Task 1); computational modeling of the physical and chemical evolution of massive stars (Task 2); quantification of the injection of supernova ejecta to star-forming molecular clouds (Task 3) and protoplanetary disks (Task 4); modeling the chemical evolution of star-forming regions (Task 5); determining what elements might be used as observational proxies in stellar spectra for elements and isotopes not amenable to direct observation (Task 6); and incorporate element abundance data in the “HabCat” of nearby stars that could support life (Task 7).
Notable highlights in the project year included work by ASU Co-I Meenakshi Wadhwa’s group showing that 60Fe was less abundant in the early Solar System than previously thought (Task 1); ASU Co-I Steven Desch’s work showing conclusively that supernovae can contaminate molecular clouds (Task 3); and insights from ASU collaborator Patrick Young’s efforts into the nucleosynthesis of the bioessential elements calcium and iron (Task 6). Perhaps the most novel contribution emerged from Task 7, where ASU Co-I Frank Timmes, ASU graduate student Natalie Hinkel and collaborator Maggie Turnbull produced the first element abundance maps of potentially habitable nearby stars (a subset of Turnbull’s “HabCat”). This new data synthesis may guide future efforts to identify habitable worlds beyond the Solar System.
Education and Public Outreach
We pursued a range of EPO activities, including significant advances on three innovative new EPO efforts that we hope will be standard-setting in the community. These activities reached a variety of constituencies, including K-12 children and educators, college students, and the public at large. Two notable activities are highlighted below:
- Our development of media-rich, immersive “virtual field trips” reached a milestone with the completion of the “beta version” of the Edicara (Flinders) VFT, produced in collaboration with the MIT Team, the Australian Centre for Astrobiology (ACA), and the South Australia Museum. This VFT featured imagery of the Ediacaran fossils from the Flinders Ranges in South Australia. We also undertook development of a new VFT in Shark Bay, Western Australia, participating in an expedition with the MIT Team and the ACA in June, 2011. An “alpha” version of this VFT, coded in HTML5, was being prepared at the end of the reporting period. These products can be found at: http://vft.asu.edu./ also participated in planning of an Iceland VFT. Also at the end of the reporting period, Mr. Geoffrey Bruce, the technologist who produces these products, became an ASU employee, and the VFT team initiated discussions with NAI central to implement a formal assessment of this EPO product.
- PI Anbar offered a new course, Habitable Worlds, as a hybrid face-to-face and online course for ~ 30 students in Fall, 2010, and oversaw development of a fully online version for ~ 160 students in Fall, 2011. He was aided by Bruce and by Dr. Lev Horodyskyj, a recent PhD from the Penn State Astrobiology Program. Horodyskyj was supported by ASU Astrobiology funds in 2010 and by ASU Online in 2011. Habitable Worlds is a general science course for non-science majors. It uses the Drake Equation as the organizing framework to cover topics ranging from astrophysics to sustainability. The course involves a number of innovative technologies. Importantly, it is being built via a collaboration between ASU and an Australian startup company that was catalyzed by Carol Oliver of the ACA.
Leadership of our EPO team transitioned from Wendy Taylor to Sheri Klug, as Taylor transitioned full time to an NSF-funded project at ASU.
As in past years, the ASU Team helped build the astrobiology community in a variety of ways, not all of which are captured in the standard reporting framework. Notable activities included:
- Co-I (and Deputy PI) Steven Desch spent Fall, 2010 on sabbatical at the University of Hawai’I, hosted by UH Team PI Karen Meech. This visit sparked several research and EPO collaborations between the teams.
- PI Anbar and Collaborator Chris DuPont of the Venter Institute worked with MSU PI John Peters to organize the workshop “Paleobiology in the Genomics Era”, held in May, 2011. This workshop focused on building bridges between genomic and geochemical insights into ancient ecology and evolution. The workshop involved a number of other members of the Astrobiology community, as well as ASU Team members Jason Raymond, Tim Lyons and Gordon Love.
- A number of members of the astrobiology community were involved in a workshop and large public event on the theme of the Origin of Life, sponsored by the ASU Origins Initiative, in February, 2011.