“Sudden pale, milky, glowing waters”; this is how sailors of yore in the 90’s used to describe the phenomenon. Although the tales might date further back in time than we know, modern scientists are still looking into the mysterious subject, having discovered interesting aspects in the last decade. Furthermore, the first satellite discovery of this phenomenon was reported just a bit over a decade, in 2005, where a report was published by the Naval Research Laboratory’s Marine Meteorology Division (NRL) in Monterey, California.

Going back in the 17th century, the so-called “milky seas” were thought to be purely linked to uncertainties of human perception and maritime folklore. Nowadays, although the specific cause of this mysterious activity remains unknown, we know that the milky seas can be so large and luminous that they are visible from space. The NRL wrote that the phenomenon explained in their paper has been detected by the Operational Linescan System (OLS) instrument, which was designed primarily to monitor global cloudiness under both solar and lunar illumination. Curiously enough, in 2005, OLS was able to detect bioluminescence for the first time, with no reports of a precedent. Enhancement of the OLS imagery revealed a massive region of low-level light emission, which lasted for three whole nights.

So what do the milky seas look like? Although the light is usually described as white (hence the “milky”), it is in fact blue. The human night-time vision perceives it as white, and the rod photoreceptors are not able to distinguish the colours. Continuing on the aspect of this phenomenon, a closer look gets us to the question: what really makes the colour so luminescent? Trillions and trillions of bacteria gather around and glow with a continuous light if under ideal conditions. One luminous bacteria that transforms chemical energy into light energy and that is thought to be responsible for this phenomenon is Vibrio harveyi. What still intrigues the scientists today is the fact that bacteria would need to reach very high concentrations in order to accumulate the chemical that induces light production. Moreover, these high concentrations would not tend to occur in natural conditions, such as in the sea. The mystery digs up deeper into the biology of this phenomenon, but since these events occur rarely and within a limited geographic range, we can assume that the bloom of bacteria can be triggered by special circumstances.

Although the luminous waters have a long, elusive background, there only have been 235 documented sighting since 1915, mainly concentrated in the Indian Ocean and around Indonesia. Slowly but steadily, we are starting to discover more about the deep waters and their mysteries. There is no prediction in regards to what the next breakthrough might look like for these strange phenomena, but properly equipped research vessels and low-light detectors on satellite systems are the main focus areas for further scientific development. Meanwhile, let’s all acknowledge the contribution made in 1870’s about the milky seas: Jules Verne’s very “Twenty Thousand Leagues Under The Sea” novel. His explanation of the “large extent of white wavelets” and all of his scientific mentionings coincide with the current findings. Coincidentally or not, even more strange is the fact that both the NRL observations and Verne’s observations take place on January 27th, more than 100 years apart.

The mystery continues… but there is no actual milk found in the sea.


Written by Alexandra Caramizaru

Edited by Yoo Jin Bae




Works Cited


Miller, S.D., S.H.D. Haddock, C.D. Elvidge, T.F. Lee. (2005) Detection of a bioluminescent milky sea from space. Proc. Nat. Acad. Sci. 102:14181-14184.



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