title: Modeling pN2through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures.
abstract: Nitrogen is a major nutrient for all life on Earth and could plausibly play a similar role in extraterrestrial biospheres. The major reservoir of nitrogen at Earth's surface is atmospheric N2, but recent studies have proposed that the size of this reservoir may have fluctuated significantly over the course of Earth's history with particularly low levels in the Neoarchean-presumably as a result of biological activity. We used a biogeochemical box model to test which conditions are necessary to cause large swings in atmospheric N2pressure. Parameters for our model are constrained by observations of modern Earth and reconstructions of biomass burial and oxidative weathering in deep time. A 1-D climate model was used to model potential effects on atmospheric climate. In a second set of tests, we perturbed our box model to investigate which parameters have the greatest impact on the evolution of atmospheric pN2and consider possible implications for nitrogen cycling on other planets. Our results suggest that (a) a high rate of biomass burial would have been needed in the Archean to draw down atmospheric pN2to less than half modern levels, (b) the resulting effect on temperature could probably have been compensated by increasing solar luminosity and a mild increase in pCO2, and (c) atmospheric oxygenation could have initiated a stepwise pN2rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN2swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N2and O2is a signature of an oxygen-producing biosphere. Key Words: Biosignatures-Early Earth-Planetary atmospheres. Astrobiology 16, 949-963.
authors.affiliation: 1 Department of Earth and Space Sciences and Astrobiology Program, University of Washington , Seattle, Washington, USA .|2 Department of Earth Sciences, University of California , Riverside, California, USA .|3 Department of Earth and Environmental Sciences, University of St Andrews , St Andrews, Scotland, UK .|4 NASA Astrobiology Institute's Virtual Planetary Laboratory , Seattle, Washington, USA .
authors.forename: E E
authors.initials: EE
authors.lastname: Stüeken
authors.affiliation: 1 Department of Earth and Space Sciences and Astrobiology Program, University of Washington , Seattle, Washington, USA .|4 NASA Astrobiology Institute's Virtual Planetary Laboratory , Seattle, Washington, USA .
authors.forename: M A
authors.initials: MA
authors.lastname: Kipp
authors.affiliation: 1 Department of Earth and Space Sciences and Astrobiology Program, University of Washington , Seattle, Washington, USA .|4 NASA Astrobiology Institute's Virtual Planetary Laboratory , Seattle, Washington, USA .
authors.forename: M C
authors.initials: MC
authors.lastname: Koehler
authors.affiliation: 2 Department of Earth Sciences, University of California , Riverside, California, USA .|4 NASA Astrobiology Institute's Virtual Planetary Laboratory , Seattle, Washington, USA .|5 Department of Astronomy and Astrobiology Program, University of Washington , Seattle, Washington, USA .
authors.forename: E W
authors.initials: EW
authors.lastname: Schwieterman
authors.affiliation: 6 School of Earth and Ocean Sciences, University of Victoria , Victoria, Canada .
authors.forename: B
authors.initials: B
authors.lastname: Johnson
authors.affiliation: 1 Department of Earth and Space Sciences and Astrobiology Program, University of Washington , Seattle, Washington, USA .|4 NASA Astrobiology Institute's Virtual Planetary Laboratory , Seattle, Washington, USA .
authors.forename: R
authors.initials: R
authors.lastname: Buick
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001272:Atmosphere; D002244:Carbon / Q000032:analysis; D002980:Climate; D018534:Earth, Planet; D018559:Exobiology; D005844:Geology; D008962:Models, Theoretical; D009584:Nitrogen / Q000032:analysis*; D013997:Time Factors
chemical_list: D002244:Carbon; D009584:Nitrogen