On February 5, 1974, NASA's Mariner 10 returned this surprising image of Venus. The photograph was the first to record our neighboring planet's clouds in such detail, polar vortex and all.
NASA isn't above a little bit of image manipulation, though. In real color, Venus looks like this:
To generate the sharp, contrasty visage, Mariner's UV camera filter blocked some of the haze reflected by high level clouds, while NASA "color-enhanced" the final image.