Life on Mars is a conspiracy theory that extraterrestrial life does exist on Mars and that NASA has been covering it up.
From what appear to be aliens and weird formations that resemble pyramids there seems to be some crazy stuff in some of the pictures from Mars rovers. Many believe that these aliens might be the Anunnaki and that they might have built the pyramid formations on Mars.
One notable conspiracy theorist who says that NASA has been covering up life on Mars is Andrew Basiago. He claims that because methane was found on Mars that there is a good chance that life is there too. He says that there are many organisms on Mars and that the government is covering up the findings and hiding the existence of a humanoid species of extraterrestrials that inhabit the planet.
Scientists believe Mars may have once held been a habitable world. Indeed there is evidence to suggest that life, or at the very least, water existed. In the 1800s the theory that life still existed emerged. William Whewell
believed he spotted Canals on Mars. However the belief was, for the most part, quelled by William Wallace Campbell in 1894 when he showed there was neither water or oxygen present.