I'm doing some research for a sci-fi story that I'm writing and hoping that some of you chemists can help me answer a quick question about the material of a hypothetical distant planet. If a distant planet were three times the size of earth with the same gravitational pull, what would the planet's material be like? Would it have to be gaseous? Is there any situation in which it would be firm enough for earth-like life forms to walk on? Is there a version where the material is something like quicksand? Please excuse my ignorance! Thanks in advance for your help.