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How does Neptune compare with Uranus in mass and density?

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Clouds in Neptune's atmosphere — Neptune A photograph of clouds in Neptune's atmosphere, taken by Voyager 2 in August 1989. The view is from below the planet's equator, and north is up. The Great Dark Spot (center left) is 13,000 km (8,100 miles)—about the diameter of Earth—in its longer dimension. Accompanying it are bright, wispy clouds thought to comprise methane ice crystals. At higher southern latitudes lies a smaller, eye-shaped dark spot with a light core (bottom left). Just above that spot is a bright cloud dubbed Scooter. Each of these cloud features was seen to travel eastward but at a different rate, the Great Dark Spot moving the slowest.

Neptune is more massive than Uranus, despite being slightly smaller in diameter. Regarding density, Neptune is the densest of the giant planets, with a mean density roughly 25 percent higher than that of Uranus.12

This higher density suggests that a larger percentage of Neptune’s interior is composed of molten rocky materials and melted ices compared to the other giant planets.2