via we-are-star-stuff - The greatest mysteries of the planets
Planets are expected to radiate heat leftover inside them from their fiery formation process, but puzzlingly, Uranus radiates little or no heat into space. Perhaps the seventh planet’s heat got unleashed during some cosmic smash-up in the distant past. That collision could also have caused the planet’s strange sideways spin. Or maybe Uranus somehow self-insulates, keeping all its heat trapped inside.
Uranus also drags around with it the craggiest astronomical object known to man - a satellite called Miranda. This strange moon has deep canyons, scrapes, terraced layers and a cliff some 12.4 miles (20 kilometers) deep – the deepest in the solar system. Miranda’s geological mess may have formed from flowing ices in the moon’s interior, perhaps heated by gravitational squeezing from Uranus and other moons, oozing out onto the surface. Or, perhaps the moon was shattered several times and came back together, creating its jagged and mottled features.