On this page you’ll find information about past and upcoming seminars related to astrobiology at Georgia Tech.
Geochemical Controls on Protocell Self-Assembly in the Origins of Life
Prof. Nita Sahai, Department of Polymer Science; Department of Geology; and Integrated Bioscience Program, University of Akron, Akron, OH
March 1, 10:50-11:50 Ford ES&T L1205
The focus of our work is to determine the constraints placed by atmosphere-water-rock interactions on the environmental conditions for self-assembly of the molecular building blocks of the earliest like-like entities, “protocells.” We have addressed the problem that modern geochemical concentrations of total dissolved phosphate (PT) and Mg2+ are much lower than those are required for non-enzyamtic (prebiotic) RNA synthesis, while Mg2 and Ca2+ concentrations are too high for membrane stability, so how did life emerge on early Earth? We used a geochemical thermodynamic modeling approach, to show that a single, globally-occurring geological process of komatiite rock weathering and evaporation of the resulting solutions under specific partial pressures of atmospheric CO2 (PCO2) can quantitatively provide the PT, Mg2+ and Ca2+ concentrations required for nucleotide synthesis, RNA polymerization and protocell-membrane stability. Conversely, the biologically-required concentrations of PT, Mg2+ and Ca2+ place constraints on the PCO2 levels on early Earth compared to previous estimates ranging over five orders of magnitude. Using these environmental constraints on Mg2+ and Ca2+ concentrations, we examined the stability and evolution of simple protocell membranes from pure single chain amphiphile (SCA) compositions through mixed SCA-phospholipid (PL) to pure PL compositions found in modern cells. We showed that, rather than acting being toxic, the divalent cations promoted evolution of the membranes towards more modern compositions. We also found that RNA oligomer synthesis is possible even at much lower concentrations of Mg2+ than previously reported, well within the concentration range constrained by the atmosphere-water-rock interactions. Thus, we have used a geochemical modeling approach to create the components of a simple protocell under geochemically plausible conditions.
Metabolic Evolution and the Self-Organization of the Biosphere
Rogier Braakman, Simons Foundation Fellow of the Life Sciences Research Foundation; Department of Civil and Environmental Engineering; Department of Earth, Atmospheric and Planetary Sciences; Massachusetts Institute of Technology
Cohosted by Biology and Earth & Atmospheric Sciences
September 14, 11:00, Engineered Biosystems Building
Metabolism is the biochemical network that supplies the energy and building blocks for all cells on Earth. The collective metabolism of all cells in turn mediates the global biogeochemical cycles, which regulate Earth’s climate. Reconstructing metabolic evolution provides a powerful lens for linking evolutionary dynamics across levels of biological organization and for understanding the chemical co-evolution of Earth and the biosphere. I will illustrate these ideas using globally abundant oceanic phytoplankton and co-occurring bacteria as a model system. I will argue the macroevolution of this system drew down nutrients in the surface oceans, thereby increasing total ecosystem biomass, while also increasing levels of dissolved organic carbon. I will further argue this evolutionary dynamic produced a collective mutualism in oceanic microbial ecosystems that is highly similar to that of organelles within plant cells. Finally I will argue that the evolutionary self-organization of oceanic microbial ecosystems contributed to the oxygenation of Earth, and more generally that the rise of atmospheric oxygen reflects an increasing metabolic rate of the biosphere.
October 18-19, Georgia Tech Global Learning Center
“The Georgia Department of Economic Development and Georgia Tech Center for Space Technology & Research are hosting a one-day symposium at the Georgia Tech Global Learning Center in Atlanta, GA. The symposium is planning a combination of technical presentations, panel discussions and guest speakers to highlight recent innovations in space science and technology.”
Explaining the Origin of Life: What’s the Question?
Eric Smith, Professor, Santa Fe institute
November 20, 3:00, Marcus Nanotechnology Building 1116-1118
The attempt to understand how and why Life emerged on Earth has been an approachable scientific question since the 1930s. However, what we think that question is, and what counts as an answer, have continually changed as our understandings of biology and of planetary and space chemistry have repeatedly been overturned. In this talk I will review four approaches to the problem of life’s origin, each anchored in a paradigm-changing discovery about nature but also to some extent reflecting traditional viewpoints from different disciplines. One approach focuses on the molecules of life and how to make them. A second emphasizes the capacity of Darwinian evolution to shape matter, and the particular role of nucleic acids in carrying the evolutionary process on Earth. A third emphasizes the intricate embedding of the biosphere within geochemistry and planetary energetics, and interprets the invariance of these relations over geological timescales as evidence of constraints on the possibilities for both living matter and evolution. The fourth approach, emphasizing the problem of Life’s robustness, is still mostly passed over both in biology and in Origin of Life, but lessons learned in physics about the hierarchy of matter suggest that it is as fundamental as the other three. From each new point of view, the requirements for an explanation of Life’s emergence have changed. Regarding them together, we can arrive at a provisional definition of the nature of the living state that is at once commonsense, but surprisingly far-removed from the definitions that were thought to be adequate a century ago.
Chance, Necessity, and the Origins of Life
Chemical and Biomolecular Engineering Seminar
Dr. Robert Hazen, Carnegie Institution for Science
November 29, 3:00, College of Computing (Room 016)
Reception to follow at 4:00 in ES&T L1 Atrium
Earth’s 4.5 billion-year history is a complex tale of deterministic physical and chemical processes, as well as “frozen accidents.” This history is preserved most vividly in mineral species, as explored in new approaches called “mineral evolution” and “mineral ecology.”
This lecture will explore possible roles of mineral surfaces in life’s origins, including molecular synthesis, protection, selection, concentration, and templating. We find that Earth’s changing near-surface mineralogy reflects the co-evolving geosphere and biosphere in a variety of surprising ways that touch on life’s origins. Recent research adds two important insights to this discussion. First, chance versus necessity is an inherently false dichotomy when considering the possibility of life on other worlds—a range of probabilities exists for many natural events. Second, given the astonishing combinatorial chemical richness of early Earth, chemical events that are extremely rare may, nevertheless, be deterministic on time scales of a billion years.
Big-Data Mineralogy: Visualizing Mineral Systems in Space and Time
Earth and Atmospheric Sciences Seminar
Dr. Robert Hazen, Carnegie Institution for Science
November 30, ES&T L1205, 11:00
A fundamental goal of mineralogy and petrology is the deep understanding of mineral phase relationships and the consequent spatial and temporal patterns of mineral diversity and distribution in rocks, ore bodies, sediments, meteorites, and other natural polycrystalline materials. Large and growing databases of mineral species, properties, localities, and co-occurrence provide opportunities for data-driven discovery in mineralogy, including the prediction of new mineral species and ore deposits.
Data-driven discovery depends on three key developments: (1) enhanced data resources in mineralogy and petrology; (2) development and implementation of analytical and visualization methods; and (3) creative framing of questions related to mineral diversity, distribution, and co-occurrence in space and time.
We are especially interested in visualization methods that illustrate multiple attributes of complex mineral systems. In particular, network analysis provides a dynamic, quantitative, and predictive visualization framework for employing “big data” to explore complex and otherwise hidden higher-dimensional patterns of diversity and distribution in such mineral systems. Mineral networks (see Figure) facilitate quantitative comparison of lithologies from different planets and moons, analysis of coexistence patterns simultaneously among hundreds of mineral species and their localities, exploration of varied paragenetic modes of mineral groups, and investigation of changing patterns of mineral occurrence through deep time. Mineral network analysis, furthermore, represents an effective visual approach to teaching and learning in mineralogy and petrology.