English: High-altitude aircraft leave behind condensation trails, or contrails, which form when extra water vapor is injected into the atmosphere through the aircraft's exhaust. The water vapor condenses and freezes around tiny particles (aerosols) that are also injected into the atmosphere from aircraft exhaust. On February 9, 2015 the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA�s Terra satellite captured this true-color image. Aircraft flying high over a large bank of clouds marked their paths with multiple contrails. The contrails are far enough above the clouds that they cast dark shadows on the clouds below. Viewed at higher resolution, it is easier to distinguish shadow from contrail: the contrail itself appears light white, and in some areas has spread horizontally. The shadow, however, appears as dark lines on the white cloud background.