A Closer Look at the 'Smiley Face' Discovery The smiley face ... but its cameras also provide detailed images of the surface.

World Smile Day is marked each year on the first Friday in October.The day came into existence thanks to US artist Harvey Ball who famously invented the iconic yellow smiley face back in 1963.

To the casual observer, it is just a photo of a man holding up a smiley face - an image used hundreds of millions of times a day in messages across the world to say "happy". But this smiley face ...