Principal Naked-Eye Lunar Surface Formations
Principal Naked-Eye Lunar Surface Formations
Principal Naked-Eye Lunar Surface Features
- The Moon’s surface has various distinctive features that can be observed without telescopic aid, referred to as naked-eye lunar surface formations.
Lunar Maria
- The dark areas visible on the Moon are called Maria, plural for Mare.
- They cover about 16% of the lunar surface, mainly on the near side visible from Earth.
- Maria are flat, basaltic plains associated with ancient volcanic activity; they are younger than most other lunar features.
- The largest Mare, Oceanus Procellarum, covers an area larger than France.
Lunar Highlands
- The bright regions on the lunar surface are known as the lunar highlands or terrae.
- They are heavily cratered and older than the Maria.
- Lunar highlands are composed mainly of a rock called Anorthosite, and most of the rocks brought back by the Apollo missions are from the highlands.
Lunar Craters
- Most obvious are the lunar craters, circular depressions on the surface of the Moon.
- They differ vastly in size, with diameters ranging from small pits to expansive basins several 100km across.
- Craters are named after notable scientists, engineers or explorers, e.g. Copernicus and Tycho.
- The largest basin on the Moon visible from Earth is Imbrium Basin, with a diameter of around 1,145 kilometres.
- Lunar craters were primarily formed by the impact of meteors and asteroids.
- Some features within larger craters, such as central peaks and terraced walls, can only be observed with the aid of a telescope.
Lunar Rays
- Many craters are associated with a system of bright streaks radiating from the point of impact, known as lunar rays.
- Rays can be several times longer than the diameters of the craters they originate from.
- Tycho crater is notable for its prominent system of rays, which extends across much of the lunar near side.
The combination of these surface features gives the Moon a mottled, contrast-rich appearance from a naked-eye perspective. Being aware of these basic features can enhance your overall understanding of the Moon and its geologic history.