Giant ice disc appears in Presumpscot River, Westbrook

A rare giant ice disc, which is approximately 91m (298ft) wide, has appeared in a river in the US state of Maine.

It formed naturally and has been slowly spinning, drawing comparisons to the Moon and even an alien spaceship.

Researchers believe ice discs spin because of temperature changes in the water, creating a vortex underneath.

The movement chips away the edges, creating its circular shape.