How is it possible that there is water ice on Mercury's surface?
I don't understand this.
Are the poles never exposed to the sun's rays?

It seems that some polar craters are in permanent shadow. Water vapour might freeze and persist in such environments.

While in contrast a portion of mountain range in the moon's polar regions is apparently in permanent sunlight. Ideal for a solar power generating station.

wouldn't space be a more ideal place for solar power generation? if we have the tech to colonize mercury, we may as well just figure out a way to life in space.

--my two cents