Antarctica is one of the best places in the world to observe rare optical phenomena. While working on the lidar systems here at McMurdo station, Antarctica, we have encountered a wide range of these effects. They are driven by ice crystals, extreme temperatures, and other atmospheric conditions. This is the first post in a series detailing optical phenomena we have observed.

The Fata Morgana pictured above can be seen at the base of the mountains. There is a band of illusion at the bottom of the mountains, where images are repeated and inverted. Fata Morgana can create rapidly changing, shimmering structures and illusions. Also pictured are penguins near the base of the mountains on the right.

Fata Morgana is a rare illusion throughout most of the world, but it is more common in polar regions and deserts (Antarctica is both). Fata Morgana occurs when light passes through a strong temperature inversion over a long distance. In Antarctica, the cold surface and stable atmosphere often set up such temperature inversions, creating perfect conditions for Fata Morgana to occur. Light rays passing through the temperature inversion are actually bent (refracted) due to the differing densities of the air. Refraction always occurs when light passes through layers of air with different densities, but usually at insignificant levels. However, there are times when the thermal inversion is strong enough, the difference in air density great enough, to bend the light rays more than the curve of the Earth. If the curvature of the light rays is greater than the curvature of the Earth, your eyes capture light that would normally have passed above you, and your brain misinterprets where the light came from and creates an optical illusion like the one pictured.

Another Fata Morgana can be seen behind the penguin in this outstanding photo captured by Griffin Perez, a photographer working at McMurdo in the galley.

Interestingly, the name Fata Morgana translates as “Fairy Morgan” or “Morgan the Fairy,” referring to the sorceress Morgana from Arthurian legend. The name originates from sailors near Italy who saw the illusions and believed them to be magical castles created by Morgana the sorceress. It just goes to show how magical the science of light can be!