2010 Annual Science Report
Arizona State University Reporting | SEP 2009 – AUG 2010
In 2010, the Astrobiology Program at Arizona State University made solid progress on all 19 of the major research tasks described in our CAN5 proposal, exceptional progress on some, and initiated new efforts in several areas. These efforts resulted in ~ 70 publications that appeared in print, were submitted or reached an advanced state of preparation during the reporting period, as well as ~ 50 professional presentations. These included several publications in high-profile journals. Collectively, this initial 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. These research advances are summarized below.
In addition to this research, a vibrant suite of EPO activities was undertaken, and some EPO flagship efforts were initiated. These activities reached a variety of constituencies, including K-12 children and educators, college students, and the public at large. Our EPO activities are also summarized below.
Our successful progress in research and EPO efforts built on, and fed into, the vibrant astrobiology research-and-education community that is now flourishing at ASU, tangibly enhanced by the CAN5 award. One notable example: the loosely organized, informal weekly gathering that was begun during the last reporting period has now blossomed into a regular weekly coffee hour/forum at which students, postdocs and visitors present research and ideas that cross-fertilize our broad group of disciplines. Attendance at this gathering rarely dipped below 15, and often reached 30 or so (taxing the capacity of the room). Excitingly, this meeting is dominated by students and postdocs from specialties ranging from astrophysics to zoology, who have taken ownership of the activity (it was coordinated this past year by one of our postdocs). As the reporting period drew to a close, and as our HD videocon system finally came on line, these students and postdocs began to reach out in an organic way to participate in meetings of the wider NAI community.
During the reporting period we also advanced our interactions with other NAI Teams and developed new collaborations with organizations outside the NAI. For example, we:
- began a partnership with the MIT Team, the Australian Centre for Astrobiology (ACA) and the South Australian Museum, to develop a virtual field trip of the Ediacara fauna, centered on a field trip in April, 2010;
- organized and participated in the Gordon Research Conference on Environmental Bioinorganic Chemistry. PI Anbar was the co-chair. Speaking participants from our team included Postdoctoral Fellow Jade Bond, Graduate Student Jennifer Glass, collaborators Jennifer Pett-Ridge and Eric Boyd, Co-I Tim Lyons, and MSU Team PI John Peters;
- deepened research collaborations with the MSU Team in studies of metalloenzyme evolution and microbial ecology through a visiting research seminar by Co-I Elser, collaborative field studies of Robertson Glacier involving Co-I Shock and others from ASU, and PI Anbar’s participation as a visiting reviewer of the annual meeting of the MSU Team in February, 2010;
- worked with researchers in the PSU Team to develop an NAI-sponsored workshop on Anaerobic Photoautotrophic Ecosytems to be held in October, 2010 (co-organized by PI Anbar);
- participated in NAI workshops, such as Co-I Desch’s presentation at the Seattle workship “Revisiting the Habitable Zone” in August, 2010;
- developed new collaborations with the USGS and Emory University via NAI DDF awards, with the U. Hawai’i Team via a sabbatical travel award to Co-I Steve Desch, and deepened interactions with UA and the Venter Institute via DDF awards to some collaborators Dante Lauretta and Chris DuPont;
- continued the varied and vibrant research interactions by many members of our team with researchers in other teams, particularly those at MIT, MSU, JPL, NASA Ames and PSU;
- helped develop forays that cross between “Following the Elements” and sustainability, such as through participation of PI Anbar and Co-I Lyons in an NAI-sponsored white paper on ocean anoxia, and by Co-I Elser’s spearheading ASU’s “Sustainable Phosphorus Initiative” (http://sustainablep.asu.edu/).
We developed human resources in astrobiology by providing full or partial support for 4 postdocs (2 female; 1 African-American) and 27 graduate students (11 female, 4 minorities) during the reporting period. Several of these individuals won competitive awards for their astrobiology-related research efforts, such as Graduate Student Greg Brennecka’s receipt of the Brian Mason Award of the Meteoritical Society, and Graduate Students Jorge Nunez and Jennifer Glass winning poster awards at AbSciCon2010.
Our team received ongoing support from ASU administration in these efforts. After establishing our new labs and offices in ~ 1500 sq. ft. of dedicated laboratory, office and meeting space, the university committed to renovating one room in this space, and an additional nearby larger conference room, for use with our new videoconferencing and presentation equipment. These rooms are located adjacent to the main building of the School of Earth & Space Exploration, which is the center-of-gravity for the ASU Team.
Below we summarize the research progress-to-date in each of our three major project components. We also briefly review our EPO activities, emphasizing highlights of Year 1.
The organizing principle of the “Follow the Elements” project is the need to understand the identity and use of bioessential elements by prokaryotic organisms and the distributions and abundances of these elements in potentially habitable, water-rich extraterrestrial environments. 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. The status of each task is comprehensively described in the main report. Key aspects are summarized 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 (Tasks 1a-f); field studies and associated laboratory analyses at Yellowstone National Park and Cuatro Cienegas, Mexico (Tasks 2a and 2b, respectively); evolutionary studies in the geologic and genomic records (Tasks 3a and 3b, respectively); and a modeling project to understand the connections between biogeochemical cycles of carbon, oxygen and bioessential nutrient elements in prokaryote-dominated oceans (Task 4).
Task 1, overseen by Co-I Jim Elser, grew in multiple directions, necessitating its division into 6 subtasks in this year’s report:
- In Task 1a, technician Marcia Kyle and Postdoctoral Felllow Amisha Poret-Peterson, working under the guidance of Co-I Jim Elser, carried out an initial run of nutrient-limited growth experiments in chemostats located in ~ 1000 sq ft. of our recently renovated astrobiology research labs, centered on the photoautotroph Synechocystis sp. PCC 6803. These experiments followed the physiological and molecular responses to N, P and Fe limitation, testing the ability of this organism to cope with limitations of three bioessential elements. Analysis of experimental findings is ongoing. We also began designing controlled-temperature chemostats for planned experiments on a mesophilic bacterium isolated from Cuatro Cienegas, Mexico, called Bacillus sp. m3-13.
- In Task 1b, Co-I Susanne Neuer obtained initial results on exopolymer (EPS) production by Synechococcus sp. WH8102, which we are using as a model organism for the study of aggregation and EPS production by early marine cyanobacteria.
- Dramatic progress occurred in Task 1c, as collaborator Felisa Wolfe-Simon used DDF funds and a NASA Postdoctoral Fellowship to delve into her quest for arsenic-based life at the USGS – Menlo Park under the mentorship of Ron Oremland. This project rapidly yielded evidence of As substitution for P by a bacterium isolated from Mono Lake, CA (Figure 1), resulting in a submission to Science at the end of the reporting period.
- Task 1d, led by Graduate Student Jennifer Glass, included two projects centered on the uptake, storage and use of molybdenum by the N2 fixer Nostoc sp. PCC 7120 in the laboratory and the role of molybdenum in limiting nitrate assimilation in a field study at Castle Lake, CA. Several publications are in print, review and preparation from this effort.
- Task 1e is a new laboratory experimental study organized by a number of ASU graduate students to examine uptake of iron nanoparticles by diatoms. The research sheds light on the mechanisms for metal acquisition.
- Unlike the other subtasks, Task 1f is a concept study rather than an experimental study, exploring the connections between changes in environmental oxygenation through time, availability of nickel and molybdenum, and the evolution of molybdenum-based nitrogenase. It is being pursued by Anbar, Glass and MSU Astrobiology Postdoctoral Fellow Eric Boyd.
Activities for Task 2a, led by Co-I Everett Shock and Collaborator Hilairy Hartnett, included analyses of the many samples collected during the 2009 field expedition to Yellowstone National Park (YNP), which include natural water and biomass samples as well as samples from a variety of incubation experiments aimed at understanding the effects of bioessential element availability on these extreme ecosystems. Postdoctoral Fellow Amisha Poret-Peterson spun up several additional projects centered on investigation of YNP samples, working with a small group of motivated undergraduates (Figure 2). A second YNP expedition was mounted in July and August of 2010, involving a total of ~ 30 faculty, staff and students over a two week period, following up on the initial findings from Year 1. Activities for Task 2b focused on collaborator Valeria Sousza’s optimization of extraction methods for DNA and RNA from biogenic carbonates collected during our Year 1 scouting expedition to Cuatro Cienegas. These efforts are in preparation for the mesocosm experiments planned for 2011. We also prepared for an additional scouting trip, to be led by Graduate Student Jessica Corman, in September, 2010. This trip was originally planned for May, 2010, but was postponed due to safety considerations.
Investigations into the evolutionary record of element use and cycling (Tasks 3a and b) were highly productive. Postdoctoral Fellow Brian Kendall produced trace element data from the Agouron Drill cores suggestive of the existence of “oxygen oases” along late Archean ocean margins (Figure 3). This work was published in Nature – Geoscience. Postdoctoral Fellow Chao Li led a study that argued for a redox-stratified ocean in the Ediacaran, published in Science. Tais Dahl, a Postdoctoral Fellow in the MIT Team and former visiting student at ASU, produced intriguing data suggesting a rise in O2 in the Devonian, submitted to PNAS. Various studies were undertaken to advance and apply the novel U isotope fractionation system, notably a paper in Geology that emerged from a collaboration with Stefan Weyer at U. Frankfurt. These projects were all funded heavily by other sources in addition to the NAI. Meanwhile, in the exclusive NAI project at the heart of Task 3a, postdoctoral Fellows Amy Kelly and Chao Li marched ahead in analyzing inorganic and organic geochemical tracers in samples from the mid-Proterozoic as part of an effort to sort out the coupled redox and biological states of this period of time. A highlight of Task 3b was the publication in PNAS of collaborator Chris DuPont’s work on the genomic distribution and apparent evolutionary timing of metal-binding domains in proteins.
The modeling investigations at the heart of Task 4 were continued by Co-I Watson Gregg, using GCM codes at NASA Goddard, joined by Co-I Susanne Neuer and others. Our findings continue to confirm expectations that nutrient cycling would be different in prokaryote-dominated oceans as compared to modern oceans. Ongoing work seeks to isolate the key parameters and to make use of the same computational codes to improve our understanding of putative Archean oxygen oases.
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).
Co-I Mikhail Zolotov and collaborator Mikhail Mironenko completed the development of two new codes for calculating chemical equilibria in salt-ice and salt-water systems, incorporating improved approaches to quantifying the activity of water in highly saline fluids (Task 1). A paper is in review.
In Task 2, collaborator Allen McNamara used numerical convection calculations to determine that significant mass transfer should occur between the ocean and overlying ice shell of Europa. This finding suggests that ocean chemistry could be detected at the surface of the ice layer. McNamara also found that the style of convection is highly sensitive to salinity, with implications for stability of the near surface. Results have been presented at international conferences and are being prepped for publication.
Co-I Zolotov and collaborator Ron Greeley set the stage for future efforts to assess the habitability of the Europa ocean (Task 3) through a suite of papers that assessed the stratigraphy, chemistry, and evolution of Europa’s icy crust and subterranean ocean, and finalization of initial plans for a NASA flagship orbiter mission to Europa.
Co-I Farmer and a number of ASU graduate students and collaborators, working on Task 4, continued to collect and analyze samples from siliceous hot springs in Yellowstone National Park to calibrate the ability of various analytical techniques that will be flown on MSL or future missions to extract mineralogical and compositional information from continental hydrothermal environments (Figure 4).
Highlights of Task 5 during the reporting period included a publication by Graduate Student Chris Glein that used observations of D/H in CH4 in Titan’s atmosphere to argue that this CH4 must have been introduced during accretion rather than produced by hydrothermal reactions. Glein, working with Co-I Shock, also finalized a study analyzing the characteristics of the putative subsurface ocean on Enceladus, inferred from measurements of NaCl in Saturn’s E ring, while Zolotov explored the possibility that Enceladus’ plumes might reflect minimal influence from aqueous processes.
Efforts for Task 6 finally began, in which Co-I Steven Desch and others began to quantitatively assess the importance of 26Al for the formation of comparatively dry terrestrial planets like the Earth. This work included a new study by Desch in which emerging understanding of chlorine geochemistry was used to infer that the Earth today is even drier than when it formed. In parallel, Zolotov used mass balance arguments to show that water-bearing extrasolar planets should be found around stars with low C/O and Fe/O ratios.
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. A particular focus is the production and distribution of the short-lived isotope 26Al, the abundance of which may affect the distribution of water in rocky planetesimals and planets. 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).
Research in Task 1 continued to focus on high-precision Pb-Pb age dating of the earliest Solar System solids, the calcium-aluminum-rich inclusions (CAIs) found in carbonaceous chondrites. Graduate Student Greg Brennecka’s discovery of significant variations in the 238U/235U ratio in CAIs was finally published in Science. This ratio has been presumed to be uniform – an assumption which underlies Pb-Pb geochronology. The observed variations therefore lead to a significant revision of early Solar System chronology. Because the variations likely result from decay of short-lived 247Cm in the early Solar System, they also provide new constraints on the timescale of solar nebula formation and injection of supernova products.
An array of projects was pursued as part of Task 2 by Co-Is Frank Timmes, Patrick Young and several graduate students to improve our understanding of stellar evolution. These projects included new 3D simulations of core collapse supernova explosions, combined with improved treatment of nuclear reactions and hence element and isotope production, led by Graduate Student Carolina Ellinger. A key area of investigation in these studies is the effect of asymmetries and other 3D effects on the production of elements – especially 26Al (Figure 5). With graduate student Mike Pagano, Young is also pursuing observational studies of the variation in element abundances of nearby stars and in coeval populations of stars. These studies generated several papers in the Astrophysical Journal.
Task 3 and Task 4 are closely linked, under the leadership of Co-Is Desch and Timmes, working with collaborators Young and Evan Scannapieco. Task 3 saw notable progress as calculations by Postdoctoral Fellow Liubin Pan revealed that injection of supernova material into molecular clouds is quite efficient provided the ejecta are somewhat clumpy, and can account for radionuclide abundances observed in meteorites. Desch developed a detailed critique of alternative explanations for these abundances, now in press at the Astrophysical Journal. Desch, working with Postdoctoral Fellow Themis Athanassiadou, and Graduate Student Nic Ouellette, developed evidence and constraints on the necessary clumpiness of supernova ejecta.
Task 5, centered on the process of “self enrichment” of stellar clusters whereby they evolve chemically as isolated systems, advanced through the development and publication of novel models of turbulent mixing of molecular clouds during collapse and of heavy elements during the evolution of clusters. This work provides a foundation for full simulations of metal enrichment in stellar clusters.
The major goal of Task 6 is to determine what elemental proxies in stellar spectra could be used to trace the production and distribution of 26Al. Substantial progress was completed in Year 1, with the work of Ellinger and Young showing that the sulfur to silicon ratio and the abundance of phosphorus may be good tracers. The major effort in Year 2 centered on improved calculations and analyses of stellar spectra to explore this hypothesis.
Task 7 centers on creating the first 3D maps of the bioessential elements for stars within 1000 light-years of the Sun, building upon the Habitable Star Catalog (HabCat) developed by consultant Margaret Turnbull. Co-I Timmes and several students meticulously combed through spectroscopic stellar abundance data this past year to advance this effort, so far completing elemental analysis of 800 of the 17,000 stars in the HabCat (Figure 6). They also developed new software tools to facilitate this painstaking effort.
We advanced a range of EPO activities in Year 2, emphasizing informal and formal educational initiatives as well as outreach. Highlights are given below.
In informal education, we continued to leverage existing EPO efforts at ASU, particularly in the Mars Exploration Program. This collaboration enabled us to reach ~ 170 K-12 educators by joining a previously planned workshop. Similarly, we infused astrobiology into a science summer camp sponsored by ExxonMobil. However, we also began to develop distinctive activities centered on our program. These included an Astrobiology Teacher Field Institute at Yellowstone National Park (in which Montana State University was a supporting partner), in which 5 elementary and secondary education teachers studied the thermal features at the Park and were involved in collecting imagery for a planned virtual field trip. Virtual field trip development was also the motivation for a partnership with MIT and the ACA to visit the Ediacara fossil localities in the Flinders Ranges of South Australia (Figure 7). We are developing a WebQuest and a virtual field trip about the emergence of animal life documented by these fossils.
In formal education, Co-I Semken spearheaded a new collaboration with the American Geological Institute (AGI) to promote current NASA Earth science, technology, engineering, and mathematics research to grade 6-12 teachers and students nationwide as part of a revision of the AGI’s nationally distributed middle-school (Investigating Earth Systems) and high-school (EarthComm) curricula. This effort is funded by a successful NASA STEM grant, and also involves Co-I Taylor and Anbar. In a separate effort, Anbar developed a curriculum based on the search for life beyond Earth as the foundation of a new science course for non-science majors, “Habitable Worlds”. This inherently integrative course is being developed to be offered online, in a partnership with ASU Online, as a “laboratory” science course. Funding for this activity is being sought from the NSF Transforming Undergraduate Education in STEM (TUES) program (PIs: Anbar and Semken).
In outreach, ASU Team members continued to engage in a wide range of activities, across a range of scales. Primary activities in Year 2 were partnerships with the Arizona Science Center and participation in large-scale outreach events at ASU. In total, we exposed ~ 7000 people to astrobiology concepts through these events. The Astrobiology Program also supported the varied and notable outreach efforts of team members Paul Davies and Lawrence Krauss. In particular, PI Anbar was appointed an Associate Director of the ASU Origins Project, directed by Krauss, to assist in developing activities that tie the Origins Project to the natural sciences and engineering at ASU.