On April 23, 2013 NASA’s Terra satellite passed off the coast of West Africa, allowing the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard to capture a curious phenomenon over the cloud deck below. The rainbow-like discoloration that can be seen streaking across the bank of marine cumulus clouds near the center of this image is known as a “glory”.
A glory is caused by the scattering of sunlight by a cloud made of water droplets that are all roughly the same size, and is only produced when the light is just right. In order for a glory to be viewed, the observer’s anti-solar point must fall on the cloud deck below. In this case the observer is the Terra satellite, and the anti-solar point is where the sun is directly behind you – 180° from the MODIS line of sight. Water and ice particles in the cloud bend the light, breaking it into all its wavelengths, and the result is colorful flare, which may contain all of the colors of the rainbow.