Moon's split personality solved

Ancient heat imbalance may explain our Moon's two-faced appearance

- Lewis Dartnell

Contrary to what Pink Floyd say, there is no dark side of the Moon. The Moon rotates on its axis once every orbit around Earth, and so, like us, experiences day and night periods (albeit very protracted). But this tidal locking does mean that one side of the Moon always faces our planet - and there's a curious difference between the lunar near and far sides.

The near side is dominated by vast, dark plains of solidified lava – the maria or 'seas' – whereas the far side is more heavily cratered, with mountainous highlands. In fact, the almost complete lack of dark maria means the far side is actually brighter than the side facing us. The Moon has a fundamental asymmetry in its surface structure: the crust is much thicker on the far side than on the near side.