The habitability of Mars is the key to discovering Extant Life on Mars. The question of whether Mars had conditions for life to arise and persist will be explored. The planet Mars has a high probability of extant life due to the many prerequisites for life that exist on the planet, as determined by the one example we have, Earth. Further research needs to be conducted to prove extant life exists on Mars. Defining life is paramount to any discovery of biological organisms, this will be examined by comparing the fossil records of early life on Earth and the examples of extremophiles presently being studied. These facts alone are not unequivocal proof of extant life on Mars, but together they make a compelling case.