Modeling pN2 through Geological Time: Implications for Planetary Climates and Atmospheric Biosignatures

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 N2 pressure. 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 pN2 and 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 pN2 to 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 pN2 rebound through oxidative weathering. In general, life appears to be necessary for significant atmospheric pN2 swings on Earth-like planets. Our results further support the idea that an exoplanetary atmosphere rich in both N2 and O2 is a signature of an oxygen-producing biosphere.Comment: 33 pages, 11 figures, 2 tables (includes appendix), published in Astrobiolog

Putting Ethics on the Agenda for Real Estate Agents

This article uses sociological role theory to help understand ethical challenges faced by Norwegian real estate agents. The article begins with an introductory case, and then briefly examines the strengths and limitations of using legal definitions and rules for understanding real estate agency and real estate agent ethics. It goes on to argue that the ethical challenges of real estate agency can be described and understood as a system of conflicting roles with associated rights and duties, in particular sales agent, intermediary and adviser sub-roles. The arguments are developed using exploratory findings from a survey of Norwegian real estate agents and from several focus groups. The article then suggests the use of various intranet tools as a kind of action research aimed at putting ethics on the real estate agents’ agenda, working to develop a collective conscience and collective selfcriticism among the agents, and, in doing so, building bridges between academic research and the practical working world of the agents