Exploring Planets and Life

Helen Hill
Saturday, January 24, 2015

Planets and Life:
Human and Planetary Perspectives

Through the fall term of 2014 Vlada Stamenković (a Postdoctoral Fellow in the Seager Group) and Senior Researcher Mick Follows organized a fascinating and hugely successful special seminar series co-sponsored by MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS) and the Harvard's Department of Earth and Planetary Sciences exploring the nexus of planets with life, from both an anthropocentric and a planetary persceptive. The series drew together over a dozen world thought leaders, both locals from EAPS and Harvard but also including invited talks from researchers from acorss the United States. Two expert panels, hosted by the MIT Museum, helped vary the pace. A wrap-up session allowed students taking the associated class to share their projects.

The Earth’s geologic record demonstrates that the environment is naturally changing. The fossil record shows that many species did not survive major environmental changes. For a modern society to thrive, it must be aware of the grand planetary changes that can occur over hundreds to millions of years. Perhaps equally important is our genetic flexibility to adapt. In this multi- disciplinary course, a series of lectures and panel discussions explored the grand environmental changes – from a natural planetary perspective – that might endanger the survival of the species Homo sapiens.

The 12 week, ten seminar, two panel series "Planets and Life: Human and Planetary Perspectives" investigated:

  • Planetary processes that have the greatest capability to significantly alter our environment on short and long timescales, based on both our knowledge of Earth’s history and our theoretical understanding of planet evolution. We will study processes between the deep interior (e.g., volcanism, tectonics), the surface (e.g., desiccation, glaciation, erosion), the oceans (e.g., acidity, ocean volume), the atmosphere (e.g., ozone hole, oxygen levels, pollution), and the biosphere (e.g., new metabolic pathways).

  • How adaptable humans are to environmental changes based on our history as a species and our genetic adaptability.

  • How much we as a species can negatively or positively impact the crucial planetary processes that are necessary for our own survival.

To kick-off the series Andrew H. Knoll of Havard presented "Evolution on a Dynamic Planet", painting a picture of evolutionary history, inferred from fossils and phylogeny, interpretting it within a framework of Earth’s dynamic environmental development, reconstructed from geological and geochemical observations.  This was followed by a lecture from the highly entertaining speaker David H. Grinspoon from the Planetary Science Institute "Planetary Changes of the 4th Kind", with the somewhat tongue-in-cheek title: "The search for intelligent life on Earth". Videos from the other lectures are presented below with recordings of the student presentations at the end.

The Keys to Habitability

Climate, Tectonics, and the Mechanisms of Continental Glaciation Through Earth History
Dick Peltier, University of Toronto

During the most recent billion years of Earth history there have been three episodes during which the continents became covered by significant accumulations of land ice. These intervals of geological time include, from most recent to earliest, the Neogene/Quaternary, the Carboniferous and the end-Proterozoic periods. The occurrences of such extreme perturbations of planetary climate have involved a variety of mechanisms, including the continental drift induced degree of polar continentality, the variation with time of total solar irradiance, variations in the seasonal distribution of irradiance due to variations in the geometry of Earth's orbit around the Sun, the concentrations of radiatively active trace gases such as CO2 and NH4, as well as internal climate dynamical processes. In his talk Peltier discussed the current state of understanding of these three distinct episodes of continental glaciation focusing upon the apparently unique mixture of mechanisms active in each case. Especially in the case of the end-Proterozoic, many issues remain outstanding.

Light to Life
Paul Falkowski, Rutgers University

The biogeochemical cycles of H, C, N, O and S are coupled via biologically catalyzed electron transfer (redox) reactions. The metabolic processes responsible for maintaining these cycles evolved over the first ~2.4 billion years of Earth’s history in prokaryotes and form a global electronic circuit with several feedbacks. The penultimate transition was the evolution of oxygenic photosynthesis in cyanobacteria, which did not lead immediately to large-scale accumulation of the gas but fundamentally altered the nitrogen cycle. The interaction between the oxygen cycle and the nitrogen cycle in particular led to a negative feedback, in which increased production of oxygen led to decreased fixed inorganic nitrogen in the oceans. This feedback, which is supported by isotopic analyses of fixed nitrogen in sedimentary rocks from the late Archean, continues to the present; however, once sufficient oxygen accumulated in Earth’s atmosphere to allow nitrification to out-compete with denitrification, a new, stable electron “market” emerged and ultimately spread via lateral gene transfer to eukaryotic host cells, allowing the evolution of “complex” (animal) life forms. The resulting network of electron transfers led a gas composition of Earth’s atmosphere, which is far from thermodynamic equilibrium (i.e., it is an “emergent” property) and can be used as a guide to search for the presence of life on terrestrial planets outside of our solar system.

Reflections on the Biosphere as a System
Tyler Volk, NYU

In his talk, Volk conceptualized the biosphere as a 4-component system consisting of life and the 3 environmental matrices of atmosphere, ocean, and soil. Energy and matter fluxes cross its upper and lower boundaries and are essential to its workings. Also essential is the role of biological evolution, which can establish complementary metabolisms among “biochemical guilds.” Such guilds create “cycling ratios,” the ratio (taken for the biosphere or any useful sub-zone within it) between the flux of an essential nutrient into the photosynthesizers within a system and the flux across the boundaries of the zone being measured. Globally, in the case of carbon, for example, this cycling ratio is about 200. The nutrient inputs and waste outputs of various guilds make changes in the chemistry of atmosphere, ocean, and soil. Some changes involve climate. Evolutionary changes can “shove” the chemistry and climate around and other organisms must adapt. A global inadvertent effect that has proved important is the progressive “biotic enhancement of weathering.” There may be coupling between the cooling caused by this biotic enhancement of weathering and the major evolutionary transitions, such as the origin of the eukaryotic cell. In any case, an interesting challenge is to coordinate understanding of the biosphere as system with these major transitions, including the origin of culture.

Life From Inside Out
Vlada Stamenković, MIT

Processes within planetary interiors, from plate tectonics and volcanism to magnetic field generation, have been proposed to shape the habitability of Earth and planetary objects in our solar system and beyond. On the other hand, life itself can modify interior dynamics by mediating crustal properties and cycles. However, the co-evolution of life and planet interior processes is still poorly explored and is often based on unverified assumptions rather than on scientific fact. During this lecture, I will review some major concepts of how geodynamics and biological processes interact and discuss the evidence supporting or weakening those theories. After that, I will dive into three active projects of my own research within this field exploring: 1) how plate tectonics might have varied with time on Earth and on which rocky exoplanets we can expect plate tectonics, 2) how surface water and atmospheric oxygen contents are tightly linked to interior dynamics, 3) and how the emergence of life might have been geophysically-driven by the rise of hydrogen – showing preliminary results for Earth and Mars.

PANEL: The Next Great Mass Extinction

With Daniel Rothman, MIT; Andrew H. Knoll, Harvard; Hillary Young, UCSB; and Anthony Barnosky, Berkeley

Future Fights of the Homo Sapiens

Stewardship of Earth’s Natural Systems: the Next Front in Protecting Global Health
Samuel Myers, Harvard

Myers talk provided an overview of the human health impacts of our accelerating transformation of Earth’s natural systems. He provided some context with a very brief overview of humanity’s reconfiguration of natural systems and sketch recent assessments of the major risk factors currently responsible for the global burden of disease and then went on to illustrate some of the pathways, some direct, and some quite indirect, by which environmental change can threaten human health and provide examples from our group’s ongoing research in this area. In particular he argued that there is a real danger of starting to reverse the progress we have made in global health as we increasingly alter the structure and function of natural systems that underpin human health.

Environmental Dynamics of Human Evolution
Richard Potts, Smithsonian

East Africa is the source of much information about the evolution of early human ancestors. An analysis of East African environmental data and Earth’s orbital dynamics indicates that climate alternated between stable and unstable conditions over the past 5 million years. This high/low variability model shows that strong fluctuation between arid and moist environments were important in the evolution of human adaptations. The origin of early human lineages, the main transitions in early technology, and the geographic milestones in human origins coincided with prolonged intervals of intense climate variability. Climate dynamics and resource uncertainty thus likely shaped the adaptive versatility of Homo sapiens, evident in the expansion of mobile technologies, symbolic behavior, social networks, and behavioral diversity. Based on these findings, the evolution of adaptability is a key theme in understanding the origin of our species. The expression and evolving nature of adaptability is likely to be the hallmark of human persistence and dispersal beyond Earth.

Welcome to the Anthropocene

Climate Change and Hurricanes
Kerry Emanuel, MIT

Emanuel began by reviewing the evidence that we are indeed entering a new epoch in earth's climate history, and then discuss the challenges it presents for civilization. Among these challenges is the increased incidence of high-intensity hurricanes, which even today are the leading cause of insured losses among all natural disasters. He then discussed his group's research on this important and interesting phenomenon, including ideas on how their activity may change over the next century.

The Human Palate for Energy, Land, and Water Under Global Change: What and Where are the Risks?
Adam Schlosser, MIT

The future of water, energy, and land availability and their security is of paramount importance. A climacteric challenge toward the future sustainability of these precious resources is to identify where and when they may become substantially limited in the coming decades and what are the key drivers. For example, the sustainability of water resources are affected by many factors that include: population, wealth, climate - as well as interactions with energy and land use and the human systems that manage them. Yet, prediction systems are challenged by uncertainties in models and observational support as well as the practical and theoretical limits-to-prediction of the Earth's systems. This limits any one forecast of a potential future as actionable information
and the scientific community has moved toward risk-based assessments to provide a likelihood of outcomes - to the fullest extent possible. To highlight these important interactions, Schlosser presented his synopsis of recently published and ongoing analyses from experiments with the MIT Integrated System Model (IGSM) that includes modules which track land use, energy use, as well as water resources for large, managed river basins. The numerical experiments address future risks in a global context but we will also focus regional lenses over the United States and a large portion of Southern and Eastern Asia. Overall, the insights gained from these experiments point to actions, which can mitigate and/or adapt to risks and thus protect future energy, land, and water resources from undesirable futures.

PANEL: Whither the Earth: Hands off? Geoengineer? Or Biosphere 3?

With Samuel Bowring, MIT; Daniel Schrag, Harvard; David Keith, Harvard

Final Research Presentations by Students
  • Magnetic Fields and Habitability - Mary Knapp, MIT
  • Is 13CH3D a new signature of life? - Danielle Gruen, MIT
  • Challenges in the Search for Life in the Spectra of Planetary Atmospheres - Jonas Wilzewski, Harvard
  • Post-Worst Case for Humanity - Jordan Mlsna, MIT
  • Effects of Asteroid Collisions on Different Types of Planets - Molly Kosiarek, MIT
  • The Mystery of Methane on Mars - Michelle Brann, Wellesley
  • Detectability of Urban Light on the Night-side of Exoplanet - Matt Webber, MIT