Do you notice anything unusual in this picture of Mars, captured by the Viking 1 space probe in 1976?

If you see a face in this picture, you're not alone. When Viking 1 beamed this image back down to Earth, it caused a sensation. Thousands of people thought it was an extra-terrestrial monument, proving the existence of life once and for all.

Many years later, astronomers took another shot of the same area and broke the illusion.

What's going on here? How did so many people worldwide imagine a face in a jumble of rocks from another planet? The reason, of course, is pattern recognition. Humans are great at detecting faces-- we have to be to tell each other apart. But sometimes, our face-recognizing software goes a little overboard, and every time we see two spots above a horizontal line, we instantly think, "Hey, I know that pattern! It's a face!" Check out these other examples of accidental arrangements that trigger our hyperactive pattern-finding abilities.

Cliff or Face Profile? This cliff in Scotland invokes the pattern of a human face with its nose, eyebrows, smiling mouth, and chin. Boiler or Surprised Face? This old boiler looks like a shocked face, with its pattern of two eyes and a mouth. Crab or Samurai Face? This crab is famous in Japan for the face-like pattern of its shell, which resembles an angry samurai. Crater or Smiley Face? Another formation on Mars activates our pattern recognition. with two simple dots above a curved line, just like a smiley emoji.