Like rivers of liquid water, glaciers flow downhill, with tributaries joining to form larger rivers. But where water rushes, ice crawls. Alaska's Susitna Glacier revealed some of its long, grinding journey when NASA's Terra satellite passed overhead on Aug. 27. This satellite image from Terra, released Oct. 20, combines infrared, red, and green wavelengths to form a false-color image. Vegetation is red, and the glacier's surface is marbled with dirt-free blue ice and dirt-coated brown ice. Infusions of relatively clean ice push in from tributaries in the north.