Contour maps showing the planetary models with largest absolute degree of polarization as a function of α and wavelengths λ. Top: the planet models that yield the largest absolute degree of polarization |P_p| over all phase angles α and λ: phase 1 – current Earth (blue); phase 2 – thin cloud Venus (light orange); phase 3 – thick cloud Venus (dark orange); and phase 4 – current Venus (brown). Bottom: the maximum values of |P_p| of the four model planets as functions of α and λ.