A happy greeting from Mars to Earth came via The Mars Global Surveyor, a mission launched in November of 1996 by NASAs Jet Propulsion Laboratories. Mars Global Surveyor sent images of the smile on the first day of its Mapping Phase in the second week of March, 1999. Malin Space Science Systems and the Caltech built the Mars Orbiter Camera, the hi-tech camera that Global Surveyor carries onboard to snap pictures of the Red Planets surface.
Mars Global Surveyor confirms that it is indeed a unique geological formation. Viking Orbiter I first photographed this "Happy Face Crater," known as the Galle (pronounced GAL-UH) Crater, in 1976 (Viking Orbiter I photo right). The crater is named after Johann Galle, who is attributed with discovering Neptune in 1846.
Although found at the same time as the Galle Crater, the "Mars Face," overshadowed the Galle Crater in the imaginations of the public. Mars Global Surveyors camera revealed that what had looked like a giant human skull to Viking Orbiter I was actually a mundane geological formation.
Elsewhere on the Web
Mars Global Surveyor stats, facts, and links
"Happy Face" crater press release from Malin Space Science Systems
NASAs photojournal archives of planets in the solar system taken by various missions
A list of craters on Mars and their namesakes