The ancient mariners were right. Tales of 鈥渕ilky seas鈥� that glow bluish-white at night and extend as far as the horizon have been spun by sailors for centuries. Now this eerie glow has been spotted from space.
Steve Miller of the US Naval Research Laboratory in Monterey, California, found this strange phenomenon in a trawl through archives of satellite cloud-cover data. Though the effect has been reported more than 200 times since 1915, he could find only one account that documented the precise time and location of an observation 鈥� in the north-western Indian Ocean in 1995.
鈥淚 didn鈥檛 really expect to see anything in the corresponding satellite data, because the light is so weak,鈥� says Miller. 鈥淏ut serendipity intervened, and I found a possible match within 30 minutes.鈥�
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When Miller and his colleagues amplified the signal, a bright structure that followed the sea surface currents popped out. The structure spanned 15,400 square kilometres 鈥� an area the size of Connecticut, and far larger than previously estimated by sailors. What鈥檚 more, it lasted for three consecutive nights (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0507253102).
Although no one fully understands what causes this nocturnal white blanket, the favourite theory is that bioluminescence from bacteria associated with micro-algae might be responsible. From the size of area covered, Miller calculates that 4 脳 1022 bacteria would be needed to produce the light.
