plankton and micro life

On Europa 1 of Juptiters moons is covered with ice but there is a ocean under it and that could contain micro life and maybe plankton and fish. There are also marks on the surface that could be volcanic vents. Mars has canals that aliens could have built. And it has rivers but they are all dried up. There is ice in the polar caps, so what I think is alien life used to live on mars a very long time ago but then over time the the planet cooled and soon it was to cold to support life. Then all the aliens died and they left fossils and those are the fossils they found on mars.