Your knowledge in basic cosmology baffles me. Mercury. It is a rock, not lava. In fact, the dark side of mercury is the coldest place in our entire solar system. Uranus, pronounce like yur-ah-nus, not your anus, is a gas giant. There is no water or ice on it. Only gas. Like Saturn, it also has rings and moons. Bungie may have tossed physics aside when creating their worlds, but they they kept the scenery as good as they could, if you imagine Venus terraformed.