Mass and gravity
Distance from the center of the mass is as important as the mass itself when figuring out the gravity at a given planetary surface.
I found this out in high school when I was trying to figure out what the density of the mythical material comprising the fictional planetoid Basidium-X would have to be to generate a 1-G field on the surface of a thirty-mile diameter planetoid. I don't remember the answer I got, and am too lazy to do it again, but it was nowhere near as high as I thought it was going to be. I do remember in the books that tiny ancient meteorites from Basidium that landed on Earth required a wheelbarrow to haul them around.