Beautiful pictures of a "rectangular moon" over the Maine coastline have captured the attention of the Internet. John Stetson, an amateur astronomer who snapped the images, was trying to take photos of the rising moon, but instead witnessed it taking on an unsual form.

"The rising Moon looked like an iceberg... faint and shaped like a giant block of ice," Stetson told Spaceweather.com.

When the photos were posted to Facebook by the website, conspiracy theorists didn't buy the real explanation for the bizarre moon and accused the "mainstream media" of a cover up.

One person in particular took against the explanation offered, and started posting her own evidence that something strange was going on.

Another Facebook user, Brian Killburn, explained quite concisely: "That's a shadow."

So what's really going on in the image?

As atmospheric optics expert Les Cowley explained: "John says '..the Moon looked like an iceberg.' That's appropriate because this mirage is a result of cold water. The cold sea offshore of Maine cooled the air above it. Above that was warmer air – a temperature inversion and the stuff of mock-mirages. The Moon's rays passing through it bend and twist into several moon images, some upright some inverted. They combine together into the rectangular 'iceberg.'"

Normally, warmer air remains below colder air, as the sun hits the Earth and heats the surface. When this is inverted by air currents offshore, it can lead to visual distortions, as the light reflected off the moon passes through these currents.

Sorry everybody, no aliens this time.