Aliens

An alien is an inhabitant of another planet. Many aliens exist in fictional works, such as the TV series Doctor Who and Star Trek, but in real life there is no real evidence that there is any life anywhere in the universe except on earth. In the 1990s a flurry of excitement took place when some tiny fossils of microbial organisms were found on a rock that had crashed down to earth from the planet Mars, but scientists are still undecided what could have caused these and many robotic spacecraft have been sent to Mars to try to answer this fundamental question. But apart from this, there is no evidence whatsoever of alien lifeforms.