Re: Frequency of water planets
Assuming that it is true that Mars contains a vast reserve of Water Ice and possibly water itself under the suface, I think that our chances of finding water/ice planets increases to nearly 100% of those terrestrial planets that are found orbiting stars similair to our own in or just outside of the star's habital zone.
It would appear that water is a very common chemical in the cosmos... which really shouldn't be all that surpising I suppose given that hydrogen and Oxygen are probably pretty common as well.