If we want to look to the heavens for signs of life on the ice-covered ocean worlds in our Solar System, what environments on Earth could help us to constrain what to look for? Earth’s oceanic crust is one such analog, where reactions between salty water and mafic and ultramafic materials can generate chemical gradients to support microbial life. Scientific ocean drilling is the only way to open windows into this environment, allowing us to probe the subsurface to determine what microbes survive and thrive, how they get energy to live, and how they interact with their surroundings. Advances in subseafloor observatories and associated instruments have increased our ability to observe the crustal deep biosphere over space and time and enabled hypothesis-driven manipulation experiments to test microbial life. In this lecture, I will present an overview of recent flagship expeditions and parallel observatory experiments focused on the crustal deep biosphere. Topics will include a synthesis of the diversity of microbial in crust and how it varies with redox conditions and rock structure, an overview of the rates of microbial processes in various crustal settings and how they compare to water-rock reactions, and estimates of the abundance of life in this biosphere. The lecture will also emphasize what the signatures of life are in this low-energy environment, how those signatures can guide how we look for life in the Universe, and how the future of scientific ocean drilling and observatory research can continue to contribute to this quest.
MARUM Research Seminar
MARUM I, room 2070