Where on Earth is the air most polluted? Recently released images from the Terra satellite show not only areas of high pollution, but also how polluted air moves. In the above image, locations of higher air pollution are shown in red. The pollutant tracked is carbon monoxide (CO) at a height of about 5 kilometers.

Last Thursday, millions of people had an unexpectedly good view of a dark night sky. Usually, the reflection of city lights off of local air impurities makes it hard for casual observers to see more than a handful of stars from a bright urban area.