Composite by Astronaut Don Pettit from the International Space Station
Phil Plait of Discover breaks it down:
The brown and green glow over the horizon is the atmospheric aerosol layer; molecules that absorb sunlight during the day and release that energy at night. The red glow above that puzzles me; I’ve written about it before. It might be a reflection of lights from inside the space station, but I suspect it’s actually the aurora; it follows the curve of the Earth, and as you can see from the star trails the camera was pointed toward the poles — the direction you’re likely to see an aurora.
