Earth's dust ring. All-sky map showing dust clouds 'trailing' (large area, left) and 'leading' (right) Earth in its orbit around the Sun. The colours represent infrared intensity at a wave- length of 12 microns, from purple (lowest) to red (highest). The red areas at top right and bottom left are signals from the Milky Way. The clouds are part of a ring of asteroidal dust which orbits the Sun with the Earth. It is thought that the dust came from the zodiacal cloud which envelops the inner Solar System, and has become locked in a gravitational resonance with the Earth. The data were gathered by the Diffuse Infrared Background Experiment on NASA's COBE satellite.