“…The chemical composition and physical structure of Earth's ancient atmosphere are active areas of research because these properties can leave perceptible imprints on rocks (Rasmussen & Buick, 1999;Som, Catling, Harnmeijer, Polivka, & Buick, 2012;Som et al, 2016). Independent methods, including paleobarometric measurements (Busigny, Cartigny, & Philippot, 2011;Som et al, 2012;Marty, Zimmerman, Pujol, Burgess, & Philippot, 2013;Som et al, 2016;Avice et al, 2018; summarized schematically in Figure 1) and modeling efforts (Barry & Hilton, 2016;Berner, 2006;Goldblatt et al, 2009;Johnson & Goldblatt, 2017Mallik, Li, & Wiedenbeck, 2018;Stüeken, Kipp, Koehler, Schwieterman et al, 2016), have attempted to constrain pN 2 throughout Earth's history. Several nitrogen sources and sinks control the atmospheric nitrogen concentration.…”