or CD water existed on Mars and that's why we see smoothed areas that resemble dry river beds cutting through the Martian terrain.  with Mars being half the size of earth, its geothermal activity has long since ceased. this would then make any magnetosphere Mars would have had also cease. the result of that would be the solar wind blasting away the atmosphere of Mars, and as such any water would just "boil" away into space, leaving Mars as we see it today. In the past history of Mars we do see evidence of geothermal activity, I think the volcano  is called Olympic Mons, and from its base to the top it stands higher than Mt Everest. I for one do belive that when humans establish a base on Mars we will find evidence of past life on Mars, and of course with humans being on Mars, there will be then Life on Mars.........................sorry I just had to put that in.