7 Life on Mars

One of the overarching philosophies of geology is actualism – the principle that processes going on today also occurred in the past with similar results. This principle guides our interpretation of ancient rocks and the environments that formed them. My research interests lie in understanding the interactions between life in the environment during the deep history of Earth, a billion years and more ago, during a time when some of the processes occurring on Earth were very different from those of today. How do we interpret non-actualistic circumstances – events, processes, environments, or ecosystems with no modern analog? And how do we carry that understanding beyond this planet – what principles can we use to detect life on Mars?

To interpret these non-actualistic settings, I draw from limited comparisons with modern environments (e.g., field work in the Argentinean Andes and the Bahamas), from experiments (e.g., work with modern microbes), and from multi-dimensional datasets in ancient rocks (e.g., work on ancient sedimentary rocks and fossils), interpreting the results in terms of the fundamental principles of the physics and chemistry of Earth systems. Because there aren’t so very many 1-billion-year-old rocks, and none preserves a complete record, I collect whatever data are available and assemble them into a local, regional, and global framework. Because data are rather scarce, I must be interdisciplinary in my approach; my datasets include aspects of sedimentology, stratigraphy, geochemistry, paleontology, and petrology.

What did Earth look like a billion years ago? Two billion? For starters, there were no animals on the planet – they hadn’t originated yet. Marine life consisted of bacteria and algae; virtually nothing thrived on land. Episodically, the continents were flooded with seawater, resulting in huge expanses of warm, shallow oceans, and microbes constructed reefs (made of microbially-influenced structures called stromatolites, see Figure 1 for examples) on the resulting carbonate platforms (Bartley et al., 2007, 2015; Pollock et al., 2006; Kah et al., 2006, 2009, 2012). Furthermore, around a billion years ago, all the world’s continents were converging on one another, assembling into a supercontinent, called Rodinia. Aggregation of this supercontinent affected Earth’s surface profoundly; as yet, though, we have few clues to the nature and extent of these changes (Bartley et al., 2001; Kah and Bartley, 2001). In addition, the amount of oxygen in the atmosphere was lower than today and carbon dioxide levels much higher, resulting in substantial differences in carbon and oxygen cycling (Bartley and Kah, 2004; Kah and Bartley, 2011). Microbes thrived, and the fossil record that preserves them raises questions about how they are fossilized, to which modern groups they belong, and what roles they played in ancient ecosystems (Bartley et al., 2000; presentations by Cole and Manning 2005-2009; work by Selly 2012).

Recent Research Trajectory

During and since my last sabbatical, I extended my research interests in ancient sedimentary rocks to a greater diversity of geologic ages, with the aim of examining how key microbe-environment interactions, preserved in structures called stromatolites, change with time and environmental conditions. In addition, I participated in a proposal to launch a camera with the 2020 Mars rover mission. The aim of that proposal was to enhance the rover’s capacity to detect structures built by microbes, if such are preserved on the surface of Mars.

In this first research thread, I aim to compare the structures built by microbes across time and environment and determine relationships between form, texture, and chemistry that can help us interpret ancient environments. During my sabbatical, I wrote a successful proposal to the American Chemical Society’s Petroleum Research Fund, which was informed by the unanswered and emerging questions that arose from papers written before and during that sabbatical (Kah et al, 2012; Gomez et al., 2014; Bartley et al., 2015). Several students (Berger, S. Bruihler, Cowdery, Eischen, Firmin, Hilgren, Martinez, Noennig, Reiners) have worked with me on this project. Collectively, we conducted fieldwork in southern Ontario, eastern Minnesota, Death Valley, eastern California, western Nevada, southern Wyoming and the Bahamas. We examined stromatolites from nine geologic units that I hadn’t previously studied, compared these to stromatolites from previous work and from the literature, and are assembling results this year. I expect at least three manuscripts to emerge from this work. Overall, we conclude that large-scale morphology bears only a limited relationship with small-scale textures and chemistry, and that specific textures and chemistry recur through time in similar environments. This project thread has resulted in an emerging collaboration with Tom Hickson (University of St. Thomas), who is conducting parallel research in a geologic unit in Nevada. We are finding that our results are concordant and are in the beginning stages of writing a paper that will help other researchers in our field describe and interpret these microbial structures.

The second research thread was catalyzed by an invitation in 2013 to join a team of scientists who are currently working on the Mars Science Laboratory (Curiosity Rover). Their experience with Curiosity informed a need for a rover camera that makes observations at the scale of a stromatolite. The Mars 2020 rover has a principal mission of detecting life on Mars, and planetary scientists hypothesize that such biosignatures, if they exist, will take the form of a structure produced by microbes. My experience with microbially-produced sedimentary rocks on Earth made me a good candidate to join this team. Although our proposal to the 2020 mission was unsuccessful (the camera was not added to the payload), the team was invited to conduct a series of experiments to determine rover strategies that maximize the likelihood of a rover encountering and recognizing a microbial biosignature if it encounters one. This project, the Geo-Heuristic Operational Strategies Test (GHOST), has involved me and two Gustavus students (M. Adams, Schaufler). The work has resulted in one submitted manuscript (Yingst et al., in review), which has been reviewed favorably and resubmitted for final acceptance in Acta Astronautica.

Scholarship of Teaching and Learning

One of the opportunities afforded by the mandate to assess in higher education is that assessment requires that we ask questions about our teaching that are very research-like. Specifically, we ask “what is the relationship between what I do with students and what students learn as a result?” This can be a powerful research question. For me, a long-standing interest in the relationship between classroom practice and student learning has led me to give several presentations on my experiences with student-centered learning – invited presentations, conference presentations, and webinars. In 2012, I formalized my enthusiasm for this kind of work by joining the Reformed Teaching Observation Protocol (RTOP) project leadership team (I’d been a trained observer since 2010-11). This group of geoscientists led an effort to observe more than 200 individual geoscience class sessions across the country, with the aim of determining how geoscience is taught. No such inventory for the geosciences at the college level exists. The result of that work (Teasdale et al., 2017) was recently published. The main conclusion is that student-centered instruction (“active learning”) is well-developed in a substantial minority of classrooms across the country, and that class size, instructor rank/experience, institution type, gender, and level of student experience are not barriers to engaging in student-centered instruction. Our paper provides examples of student-centered practice that are achievable at nearly any scale, without “ripping up” a course and starting over. The work of this team continues, though I’ve taken a respite from the group while serving as Dean.

Leadership

As a mid-career scientist, I have participated in leadership roles within my professional community. I served as the Gustavus Chapter delegate to the Sigma Xi national meeting in 2016; have convened sessions at the Geological Society of America annual meeting (most recently in 2017). I have been invited to serve on graduate committees (most recently at the University of Cincinnati, Rutgers, and University of Missouri). I review several manuscripts for journals and proposals for funding agencies each year (fewer since I’ve been serving as Dean). In 2012, I was invited by Conoco-Philips to serve as a content expert (on stromatolites) for a field course.

Presentations

Oral and poster presentations at conferences are an important mechanism for dissemination of research results and serve as a forum for vetting ideas that are still in development. I encourage (the students might say ‘require’) student collaborators to present their results, as these opportunities are critical to their ownership of the project and to their development as emerging scientists. In addition, because not every student research project results in a journal article, the work presented at conferences allows a public forum for students to receive feedback from the community. Beyond professional meetings, talks at other colleges and universities are an important mechanism for me, particularly as a scientist from a smaller institution, to interact with colleagues and to share work in progress.

Collaborative Research

It is clear from a perusal of my vita that most of my research is conducted in collaboration with colleagues and/or students. The professional collaborations in which I have engaged have been exceedingly productive, with the final products being much more than the sum of the individuals involved. My collaborations include long-standing partnerships, such as the one with Linda Kah at the University of Tennessee, and newer ones, such as those with Tom Hickson at the University of St. Thomas and Chad Wittkop at MSU-Mankato. These collaborations have permitted me to be ambitious in my research agendas and to tackle large-scale scientific problems. They have provided opportunities for my students to interact with graduate students from several institutions. Seeing graduate work in action is enormously helpful to our students who are considering graduate school.

Because student research is central in our geology department and is important to the College, I involve students to the maximum degree feasible in each project I undertake. Even in the most remote areas that I’ve worked, undergraduates have participated in the fieldwork. The collaborative nature of my work has enabled students to travel to other institutions, to use instrumentation not available locally, and I expect that this will continue, as students develop questions that require instruments at other institutions. In addition, students from other institutions come here – for example, I’ve hosted graduate students from the University of Tennessee, who came here to collect data with our ICPMS. While she was here, she gave a presentation to our geology students about life and career opportunities after graduation.

References

Bartley, J.K., Knoll, A.H., Grotzinger, J.P., and Sergeev, V.N., 2000, Lithification and fabric genesis in precipitated stromatolites and associated peritidal carbonates, Mesoproterozoic Billyakh Group, Siberia. In: Grotzinger, J.P. and James, N.P., editors. Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World, SEPM Special Publication 67, p. 59-73.

Bartley, J.K., Semikhatov, M.A., Kaufman, A.J., Pope, M.C., Knoll, A.H., Jacobsen, S.B. 2001, Global events across the Mesoproterozoic-Neoproterozoic boundary: C and Sr isotopic evidence from Siberia. Precambrian Research: Theme Issue – Rodinia and the Mesoproterozoic Earth-Ocean System (J.K. Bartley and L.C. Kah, editors), v. 111, p. 165-202.

Bartley, J.K., and Kah, L.C. 2004, Marine carbon reservoir, Corg-Ccarb coupling, and the Mesoproterozoic carbon isotopic record: Geology v. 32, p. 129-132.

Bartley, J.K., Kah, L.C., McWilliams, J.L., and Stagner, A.F., 2007. Carbon Isotope Chemostratigraphy of the Middle Riphean type section (Avzyan Formation, Southern Urals, Russia): Signal recovery in a fold-andthrust belt. Chemical Geology v. 237, p. 211-232.

Bartley, J.K., Kah, L.C., Frank, T.D., Lyons, T.W., 2015, Deep-water microbialites of the Mesoproterozoic Dismal Lakes Group: Microbial growth, lithification, and implications for coniform stromatolites: Geobiology, v. 13, p. 15-32.

Cooley et al., 2007, Georgia Journal of Science 65:4.

Gomez, F.J., Kah, L.C., Bartley, J.K., and Astini, R.A., 2014, Mineralized microbialites in a high-altitude Andean lake as a natural analogue for Proterozoic stromatolite formation: PALAIOS, v. 29, p. 233-249.

Kah, L.C., Bartley, J.K., Frank, T.D., Lyons, T.W., 2006, Reconstructing sea level change from the internal architecture of stromatolite reefs: An example from the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada. Canadian Journal of Earth Sciences v. 43, p. 653-669.

Kah, L.C., Crawford, J.C., Bartley, J.K., Kozlov, V.I., Sergeeva, N.D., and Puchkov, V.N., 2007, Carbon isotope chemostratigraphy as a tool for verifying the age of Riphean deposits in the Kama-Belaya aulacogen, the East European Platform. Stratigraphy and Geological Correlation v. 15, p. 12-29.

Kah, L.C., Bartley, J.K., and Stagner, A.F., 2009, Reinterpreting a Proterozoic enigma: Conophyton–Jacutophyton stromatolite reefs of the Mesoproterozoic Atar Group, Mauritania: Special Publication of the International Association of Sedimentologists, v. 41, p. 277-295.

Kah, L.C., and Bartley, J.K., 2011, Protracted oxygenation of the Proterozoic biosphere: International Geology Review v. 53, p. 1424-1442.

Kah, L.C., Bartley, J.K., and *Teal, D.A., 2012, Chemostratigraphy of the Late Mesoproterozoic Atar Group, Taoudeni Basin, Mauritania: Muted isotopic variability, facies correlation, and global isotopic trends: Precambrian Research v. 200-203, p. 82-103.

Manning & Bartley, 2009, GSA Abstracts with Program 41(1):54.

Manning & Bartley, 2007, GSA Abstracts with Program 39(6):325.

Manning & Bartley, 2007, Georgia Journal of Science 65:42.

Pollock, M.D., Kah, L.C., and Bartley, J.K. 2006, Morphology of molar-tooth structures in Precambrian carbonates: Influence of substrate rheology and implications for genesis. Journal of Sedimentary Research v. 76, p. 310-323.

Pope, M.C., Bartley, J.K., Knoll, A.H., Petrov, Pay., 2003, Molar tooth structures in calcareous nodules, early Neoproterozoic Burovaya Formation, Turukhansk region, Siberia. Journal of Sedimentology v. 158, p. 235248.

Selly et al., 2012, GSA Abstracts with Program, 44(7):246.

Teasdale, R., Viskupic, K., Bartley, J.K., McConnell, D., Manduca, C., Bruckner, M., Farthing, D., and Iverson, E., 2017, A multidimensional assessment of reformed teaching practice: Geosphere, v. 13, p. 608-627.