However, it is still a mystery. This is different from UFOs as UFO are unidentified flying objects, meaning something unidentified that has been seen on earth. Some likely candidates for supporting life are Gliese 581 d and HD 189733 b, the latter supposedly containing water vapour and organic matter.
There are also questions as to whether there are moons orbiting these planets. Some people believe that there may even be life in our solar system that we don’t know of. Some moons, like Neptune’s Triton or Saturn’s Europa, may possible have, or had, life, and there is substantial evidence that water once flowed through Mars. Still, no one knows.