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.