To my knowledge, that's only been confirmed for Earth, Moon, Mars and a couple nearby asteroids. The rest is just extrapolation of our limited data. P.S. Those

To my knowledge, that's only been confirmed for Earth, Moon, Mars and a couple nearby asteroids. The rest is just extrapolation of our limited data. P.S. Those razors would better be kept in the bathroom as they only give an illusion of knowledge. P.P.S. I'd inspect material from Neptune first, in absense of better sources, such as comets.