You know, there is already plenty of evidence of water on Mars, most of it subsurface and much of it as ice. This one could be a hot water spring. If they are waiting for discovery of water, they could have stopped waiting several years ago.
No there isn't. In fact, there is just as much evidence that a large ice comet hit mars and melted, which caused these dried up riverbeds. Notice they are found in craters and on the edges of craters. It makes more sense than the solid comet hitting mars theory, uncovering ice which then melted.
One theory does not require further funding, the other does. It isn't suprizing which one "scientists" go with.