FIG. 13.
This plot shows how one could determine a lower limit on the surface or cloud-top pressure using only a transmission spectrum. (a) O2 partial pressure at maximum tangent pressure vs. the ratio of the dimer feature and O2 A band flux difference ratio. The ratio can be used to determine the O2 partial pressure. (b) fO2 (or O2 mixing ratio) vs. A band flux difference. The A band flux difference is roughly constant for a given O2 mixing ratio. (Color graphics available online at www.liebertonline.com/ast)