Umbriel is the darkest of Uranus’ largest moons. It reflects only 16 percent of the light that strikes its surface area, a aspect much like the highland parts of Earth’s moon. It had been discovered in 1610 by Galileo, with its observation, and that of another a few Galilean moons, https://moons61582.blogstival.com/56475368/best-moons-an-overview