NSF Award
2409324
Reactive nitrogen plays a pivotal role in understanding the origins of life and assessing the potential for life on other planets. Decades of research have been dedicated to unraveling the mysteries surrounding reactive nitrogen's origins and the magnitudes of its sources on early Earth. This research aims to provide evidence of the significance of hydrothermal air-water ammonia flux and characterize the chemical signatures of this process expected to appear in the rock record. Through field and laboratory experiences, the research has a broader aim of enhancing capacity and instigating transformative experiences for students and principal investigators at a Research-2 Minority Serving Institution. A key focus is to address the scarcity of hands-on research experiences available to these populations. <br/><br/>In contrast to contemporary environments where nitrate is a primary reactive nitrogen species, the reducing conditions of early Earth were characterized by the dominance of ammonia/ammonium (NH3/NH4+). Numerous hypotheses have been proposed regarding the abiotic production of ammonia. However, investigations into the potential magnitude of these abiotic mechanisms suggest their insufficiency to sustain the Archean biosphere, thereby implicating an early biotic source. Whether sourced abiotically or biotically, a continuous flux of reactive nitrogen to early habitats would have been indispensable for the origin and proliferation of life. Recent modeling efforts have suggested ammonia flux from hydrothermal features (e.g., hot springs) may have been a primary source of reactive nitrogen to the early Earth. This conceptual validation underscores the necessity for direct measurements to validate modeled ammonia flux accuracy. This research will quantify ammonia flux from hot springs, alkaline lakes, and fumaroles and determine the nitrogen isotopic composition (delta-15N) of ammonium (NH4+) and total nitrogen (N) in water and sediment sampled from these features along with the delta-15N of ammonia (NH3) in the associated atmosphere and fumaroles. This will be accomplished through developing direct and indirect NH3 flux measurement methods to sample hot springs in Yellowstone National Park and alkaline lakes in California. Flux measurements will be scaled to determine the portion of early Earth that would need to be covered by these features to produce significant NH3 flux. Nitrogen isotopic composition results from water, sediment and sediment samples will provide a foundation for exploring the existence of NH3 flux mechanisms vs. other abiotic and biotic processes documented in the delta-15N rock record and will help unravel the development of Earth’s biogeochemical N cycle. This exploration not only enhances our comprehension of terrestrial processes but also extends its reach to potential biosignatures on extraterrestrial bodies.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
