I wonder if our preconception of celestial bodies as "lumpy grey rocks" is biased by our proximity to a bunch of grey rocks. Lumpy grey rocks are common in the

I wonder if our preconception of celestial bodies as "lumpy grey rocks" is biased by our proximity to a bunch of grey rocks. Lumpy grey rocks are common in the inner solar system where rocks (Si, Ca, Mg, Fe, Al, etc.) are the only things that remain solid in the long term. It's too hot around here for anything more volatile to last without a strong magnetic field to protect them. But as you move further away from the Sun, things that we normally don't think of as "rock", such as water and methane, begin to behave like rock. If ice is rock, then water is lava, and methane rain can erode it! So we get a whole bunch of phenomena that are similar to Earth geology and weather, only with different chemicals.