The Moon was the Earth's only natural satellite. Although not the largest natural satellite in the Solar System, it was, among the satellites of major planets, the largest relative to the size of the object it orbited and, after Jupiter's satellite Io, it was the second most dense satellite among those whose densities are known.
The Moon was in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It was the most luminous object in the sky after the Sun. Although it appeared a very bright white, its surface was actually dark, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art, and mythology. The Moon's gravitational influence produced the ocean tides and the slight lengthening of the day. The Moon's current orbital distance was about thirty times the diameter of Earth, causing it to have an apparent size in the sky almost the same as that of the Sun. This allows the Moon to cover the Sun nearly precisely in total solar eclipse.
The Moon, along with Mars, were the first celestial bodies other than Earth on which humans have attempted to colonize with the advent of Robotechnology. The United Earth Government's Luna programme reached the Moon and constructed Moon Base Luna, which was in use until it was destroyed during the beginning of the Second Robotech War. A second moon-based facility, Moon Base ALICE, a civilian chemical research station, was also constructed, but repurposed as a military base to counter the Robotech Masters' fleet. By the Third Robotech War, Moon Base Luna was rebuilt, serving as the staging grounds for the Earth Reclamation Force.