Explaining Moon’s mystery bulge

Scientists have discovered why the Man in the Moon has a pot belly. They say it formed in the early days of the solar system when the Moon came much closer to the Earth.

Planet experts have been puzzled for years by a mysterious fattening in the lunar midriff. It causes a bulge at the equator on the far side of the Moon which is permanently hidden from Earth but has been pictured by astronauts and from spaceprobes.

Scientists at the Massachusetts Institute of Technology say the Moon used to travel in a peculiar oval orbit that brought it close to the Earth. Gravitation caused the molten rock inside the Moon to be pulled outwards as it was still solidifying. Today the orbit is roughly circular but the bulge is still there, the journal Science reports.

The US team used ancient records of the times of eclipses to calculate the position of our natural satellite throughout history. They say their explanation ties in with the theory that the Moon was created when an object the size of Mars collided with Earth around 4.6 billion years ago.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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