Why the Moon is shaped like a lemon
30 July 2014 Last updated at 17:54 BST
Scientists have worked out the reasons for the distorted shape of our Moon.
A US team calculated the effect on the shape of the early Moon of tidal and rotational forces.
They say its own spin and the tidal tug of the Earth created a "lemon-shaped" satellite.
Here, lead researcher Ian Garrick-Bethell from the University of California Santa Cruz explains that this shape-shifting occurred when the Moon was mostly liquid beneath a thin outer crust of rock.