NASA Goddard's Scientific Visualization Studio/T. Schindler.
Denver Comparative Imagery
Satellite data show that Denver has seen a 22 percent decrease in nitrogen dioxide between the 2005-2007 (left) and 2009-2011 (right) periods. NASA's Discover-AQ, a multi-year airborne mission, is flying this summer in Denver to learn more about the region's wide range of air pollutants.