An image taken by the Mars rover Curiosity back in September has been making the Internet rounds recently. A poster to a web forum devoted to UFO sightings suggests that the image shows "a cute rodent on Mars." This quickly morphed into claims of a squirrel sent with the rover as an experiment hidden from public scrutiny.

No word on how the squirrel-stronaut survived the 7-month trip to Mars in the vacuum of space or 52 Martian days in the largely carbon-dioxide atmosphere. I'm also not finding a "squirrel door" on the bottom of the rover.

Hobbyists and others have been seeing familiar objects among the rocks in images returned by the rovers and orbiters studying Mars for as long as those images have been beamed back to Earth.

Mars Exploration Program

There are plenty to pour over. The Curiosity rover alone has returned over 57,000 images so far. Spirit adds more than 128,000 and Opportunity nearly 180,000 images. Some days more than 1,000 images are returned.

In 2007, there was a bit of hype over an image returned by Spirit which some said captured a woman sitting on a rock in the distance. Others compared it to the iconic image of "Bigfoot" striding through the forest. Hobbyists who frequent the Planetary Society's unmannedspaceflight.com message board asked "why stop there?" Eric Hartwell compiled it all into a view of Spirit's West Valley Panorama highlighting rocks that resemble Jabba the Hutt, a tiki head, the Sphinx, a duck, a polar bear, and even a turtle on the move.

Why do we see animals, people or religious figures in rocks on Mars, clouds in the sky or our morning toast? Psychologists point to pareidolia as the cause. Pareidolia is the human ability to recognize faces, a skill that is hardwired into our brains as infants.

As long as spacecraft have been sending images back from Mars, people have been finding faces among the rocks. A grainy digital image filled with transmission errors from the Viking orbiter showing what was described as a "humanoid face" in 1977. The mission's Primary

Investigator Gerry Soffen explained it as an optical illusion. Still, tales of "Ruins of an Ancient City on Mars" quickly escalated to "Face on Mars Beams Radio Signals to Earth" in grocery store tabloids.

Tabloids weren't the only ones selling the idea of familiar formations on Mars. Vincent DiPietro, the electrical engineer credited with finding the original face image in NASA public files, sold a book on "Unusual Martian Surface Features." Here in North Carolina, newspapers tell of lectures by Emil Gaverluk of East Flat Rock on the Mars face in the mid '80s. Gaverluk added the presence of a "laser of tremendous power" to his talks about the face.

As time and technology moves on, new images have provided more scientific explanations.

When the Mars Global Surveyor and Mars Express orbiters passed over the site in 1998 and 2006, their much-improved cameras and radars returned images of the mile-wide mesa carved by landslides over many years. Those higher resolution pictures, even at the right time of day and time year, don't look very face-like though.