Hi Edwin,

When we find water on another planet, that means that life *may* have existed at one time. So the presence of water is an indication that life, such as bacteria, may have existed, but it is not proof. Proof would be if we actually found fossils or bacteria on another planet- something that has not yet happened. This is one area of research in which many scientists are extremely interested in, so we will probably learn much more about it in the years to come.

Holly