What is the "milky sea" phenomenon?

Photo by J. W. Hastings, Harvard University, through E. G. Ruby, University of Hawaii via the NSF

For hundreds of years, sailors have told tales of a mysterious event that takes place far out in the open ocean. They've recounted suddenly coming upon miles and miles of pale, milky, glowing waters, sometimes stretching as far as the eye can see. Unable to offer any legitimate explanation for this strange phenomenon, most people dismissed accounts of the milky sea as tall tales or simply figments of delirious, land-starved sailors' imaginations. The great science-fiction writer Jules Verne wasn't quite so dismissive, however, and he actually wrote a scene in his classic novel "Twenty Thousand Leagues Under the Sea" that depicts the submarine Nautilus coming across a glowing "milk sea."

Fast-forward to a more modern era, and ships are still reporting on strange seas that seem to be, as Verne put it in his book, "lactified," particularly in the Indian Ocean. Then, in 2005, a group of scientists led by Dr. Steven Miller of the Naval Research Laboratory in Monterey, Calif., decided to take a closer look at this supposed mariner's tall tale. They used data collected from satellite sensors to confirm a "milky sea" event reported in 1995 by a British merchant vessel called the S.S. Lima in the northwestern Indian Ocean.

On January 25, 1995, the Lima reported that, "on a clear moonless night while 150 [nautical] mile[s] east of the Somalian coast, a whitish glow was observed on the horizon and, after 15 minutes of steaming, the ship was completely surrounded by a sea of milky-white color with a fairly uniform luminescence … It appeared as though the ship was sailing over a field of snow or gliding over the clouds" [source: Miller].

Dr. Miller and his colleagues used the Defense Meteorological Satellite Program (DMSP) and its polar-orbiting satellites to detect the otherworldly event that the Lima's crew described. The satellite images did, indeed, reveal an area of low-level light in the northwestern Indian Ocean, about the size of Connecticut, at the date and time recorded by the S.S. Lima. Suddenly, the milky sea phenomenon didn't seem like such a tall tale.