Antarctic optical phenomena

Because of the extreme cold temperatures, both near the ground and above us, there are some pretty amazing optical phenomena to be seen. The first, and one that you will probably be familiar with is the 'sun dog'.
This phenomenon is also referred to as 'mock suns' because of the appearance of one (or, in this case, two) bright spots next to the sun. This picture also shows some of the arc around the sun, too. On this day, it was a beautiful clear day. But on walking outside, the air all around us was glittering. There were ice crystals everywhere (Not snow. Think smaller. They are referred to as 'diamond dust'.) It was these crystals that gave us such beautiful sun dogs. Ice crystals have hexagonal shapes, and as light passes through these little crystals, the light is reflected and refracted back into the viewer's line of sight, causing bright spots.

The second phenomena is really only 'optical' when there is light to interact with them, but occur when the temperatures are just right. We all know that clouds form in the troposphere (or we do now), but what if I told you that there were stratospheric clouds? My God! She must be mad! No. I'm not.
I know, I know. Not much to look at. But this is the only one I saw all season. Just before we arrived on the Ice, we were told that the sky was filled with them, causing the most beautiful sunsets you have ever seen. And boy, were they right:

This picture is in focus (see the horizon). But doesn't it look like an artist just brushed the sky with his brush? Simply amazing. This picture was taken by the station dentist, Kim. The previous one was taken by Luca who ran the LIDAR.
So what are these? They are called polar stratospheric clouds (PSCs) or nacreous clouds (when you can see them). They can only form when stratospheric temperatures are very cold (-80 degrees Celsius. That's -112 F) and at altitudes between 15 and 30 km (about 50-100,000 feet). They are composed of water and nitric acid. But not to worry, they are completely natural. We are particularly interested in these clouds because of their reaction with ozone. Long story short, these clouds produce activated chlorine which is an ozone destroyer. When these clouds are present (Antarctic winter), the ozone hole intensifies. We measured these clouds when we first got here, but they are quick to disappear due to the rapid warming of the stratosphere as we got more and more sunlight.

The last phenomenon is a personal favorite of mine: fata morgana. This is a type of mirage (superior). Inferior mirages are the ones we are most familiar with. This is what you see when driving on a hot road and there appears to be a pool of water in front of you. What is actually happening is the sunlight is being refracted, or bent. Similar to putting a straw into a glass of water and seeing that it "bends", light is bent toward the colder (denser) air. For Fata Morgana to appear, the surface temperature has to be colder than the air above it. Here is some amazing fata morgana we saw, as photographed by Luca:
Do you see that strange band of "cliffs" at the bottom of the mountains? Looks pretty fake, right? Well, it is. This is the fata morgana. Light is bent toward the colder air, but our eye interprets that as being higher than reality. Here is a nifty slide I made to try to explain it better.
Angry Man is seeing the refracted light from the mountain, but his eyes follow the same line up (they don't curve back down). So what he thinks he sees is a really tall cliff, or mountain.

I hope that makes sense. It is easier to explain in person. But that's it for Antarctic Optics, Leslie Style.