A wall of dust was barreling across northern China on April 23, 2014, when the Moderate Resolution Imaging Spectroradiometer (MODIS) acquired these images from NASA’s Aqua and Terra satellites. The top image was taken at 12:35 p.m. local time, and the lower image is from 2:20 p.m. Turn on the image comparison tool to see how far the dust advanced in the two hours between images. Read more