Often incorrectly called the "dark side" of the Moon - incorrect because it receives the same amount of sunlight as the near side - the far side of the Moon has distinct characteristics. For a start, it is more densely cratered and has fewer maria, or large, dark, basaltic plains created by early volcanic eruptions. These are called maria because they mean "seas" in Latin. Early astronomers thought the dark areas were oceans.

Why can't we see it from Earth? The Moon always faces us on the same side because it is tidally locked to our planet. This means that the Moon's orbital period is the same as its rotation around its axis. One revolution of the Moon takes exactly one month on Earth.

Image description:

The Moon's round, grey disc is pitted with craters of all sizes along its surface. This mosaic of the Moon's far side is made up of 15,000 images taken by the Lunar Reconnaissance Orbiter between November 2009 and February 2011.