Images? These are maps!
NASA has been monitoring atmospheric chemistry with the Aura spacecraft for the last 10 years. The animated GIF above shows the change in Nitrogen Dioxide over time. NO2 is formed from fuel burned at high temperatures and is an indicator of atmospheric pollution. One of the nifty features of this data is how it captured. To keep a consistent angle of sunlight (changes in which can affect atmospheric measurements), Aura is placed in a sun-synchronous orbit. This orbit passes over the poles (roughly) and crosses the area of interest at the same time, every time.
You can see more over at their website: http://aura.gsfc.nasa.gov/index.html