NASA/JPL/Malin Space Science Systems

There are other pictures of this feature on Mars, known to many as the Happy Face. But in this new image, the mouth appears suddenly wide open. Perhaps the smiling Martian is now laughing at us humans for all the analysis we do of Martian features.

The photo, taken by the Mars Global Surveyor, was released May 15. Astronomers at Malin Space Science Systems, who run the craft's Mars Orbiter Camera, say the apparent change was caused by a shifting pattern of frost distribution across existing features. The white and gray areas are fresh patches of carbon dioxide frost deposited early during winter in the southern hemisphere. Once again, scientists ruin all the fun.

The crater is named Galle and is located on the east rim of Argyre at 51°S, 31°W. Sunlight illuminates the scene from the upper left. The crater is 143 miles (230 kilometers) across. [The Real Story Behind Mysterious Space Photos]

-- Robert Roy Britt