a) Absorption cross sections of the considered atmospheric gases, Rayleigh scattering cross section of CO₂ (dashed red line), and Mie extinction cross sections for mode-1 (thick blue line) and mode-2 (thick violet line) haze particles. b) Transit spectrum of Venus transiting in front of the Sun, as seen from Earth, in relative absorption and c) effective height of absorption. The different transit spectra shown are models with no upper haze (black), mode-1 upper haze (red), and modes-1+2 upper haze (green). The top of the main cloud deck is set at 70 km. The transit spectrum of the Earth calculated by Kaltenegger & Traub (2009) is overplotted (blue) and shifted by  + 100 km for clarity.