Student: Samuel Duncanson, graduate student in Geology, Iowa State University
Faculty Advisor: Dr. Benjamin Johnson
Geochemical nitrogen cycle through Earth history
Nitrogen is an essential element for life on Earth. To better understand possible constraints on the evolution of life, therefore, requires a comprehensive picture of different components of the nitrogen cycle through time. Despite active research concerning the modern nitrogen cycle, including on crop growth and health, we lack understanding of this cycle during certain intervals in Earth history. Examples include (1) continental nitrogen concentration and isotopic signatures, and (2) biogenic nitrogen dynamics in marine environments during global glacial periods, such as the Neoproterozoic “Snowball Earth” episodes.
At Iowa State University, I will be addressing these nitrogen quandaries with Dr. Ben Johnson by measuring nitrogen concentrations and isotopic signatures from (1) modern glacial tills representative of continental nitrogen concentrations, and (2) sedimentary rocks deposited during ancient glaciations, which capture biologic nitrogen processes, and interactions between life and dynamic redox conditions. To more fully grasp the nitrogen record in these rocks, laboratory analyses measuring nitrogen and other element concentrations and isotopic signatures will be compared with crucial sedimentological observations from fieldwork. Pairing field observations with laboratory results provides the necessary framework for evaluating nitrogen signatures in respective depositional environments.
Research on nitrogen cycling through time supports NASA’s Planetary Science Research program by helping us better understand long-term planetary habitability. Specifically, nitrogen dynamics from rocks deposited during global glacial periods falls under the “Large scale environmental change and Macro-evolution” purview in the Exobiology program. In addition, biogenic nitrogen isotopic records provide additional context for the “Biosignatures and Life Elsewhere,” purview.