Fig. 2: Evolution of atmospheric O2, O3 column density and surface UV.
From: Metal-rich stars are less suitable for the evolution of life on their planets
a O2 volume fraction of the Earth’s atmosphere during the past 600 million years according to Berner et al., 200624 (B6, blue) and Lenton et al.27 (L16, light blue). The blue shaded area indicates the uncertainty range of the B6 data. b–d Surface UV-C (202 to 230 nm) b, O3 column density c and surface UV-B (280 to 315 nm) d (1 DU = 2.687 × 1020 molecules/m2). The blue and green curves are calculated with B6 and L16 data, respectively. The inserted plots show the dependencies of UV-C b, O3 column density c and UV-B d on the O2 content. c, d The level of O3 corresponding to 2% of O2 is shown by the yellow dashed line. The O3 level of 220 and 80 DU are indicated by the grey and brown dashed lines, respectively. The UV-C levels of 10−3 and 5×10−5 W/m2 are shown by the pink and red dashed lines in b. Source data are provided as a Source Data file.
