There may be evidence that there was once life on the planet Mars. This is certainly not a smoking gun, but the good folks at Astro Biology Magazine think they have stumbled upon evidence that life might have once lived on the surface of the red planet. They have analyzed images take by NASA's Curiosity rover and compared them to similar images from Earth. The structures in the images from Mars are similar to structures here on Earth that were created by micro-organisms. Does this mean that there once was life on Mars? No, but it does mean that there could have been life on Mars in the distant past. It's not a smoking gun, but it's still possible.... Read more about it here, here and here.