Class D - Asteriod/Moon
Age: 2-10 billion years
Diameter: 100 - 1,000 km
Location: Hot, Ecosphere, and Cold Zones; found primarily in orbit of larger planets or in asteroid fields
Surface: Barren and cratered
Atmosphere: None or very tenuous
Life-Forms: None known
Examples: Moon, Lunar V
Class D planets are found in any zone within a star system. Generally they are found in orbit around larger planets, or in asteroid fields. Quite small, they are no bigger than 1,000 kilometers in diameter. The surface of Class D planets is barren and heavily cratered, and no atmosphere is present, making them unsuitable for life.
Earth's Moon is Class D, as is Lunar V, the moon orbiting the fifth planet of Bajor as seen in "The Hunted" (TNG), and "The Siege" (DS9).