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Every now and then KNMI receives questions that cannot be answered adequately. Recently our attention was drawn again to a mysterious phenomenon: 'marine phosphorescent wheels'. These still unexplained phenomena are reported at sea for at least hundred years. 'Marine phosphorescent wheels' or 'oceanic light wheels' are luminous phenomena that are observed on ships especially in the Indian Ocean, Persian Gulf and the South China Sea. A lot has been written on this subject and many possible causes have surfaced, ranging from biological to seismic sources and possible connections to UFO theories and crop circles.
'Marine phosphorescent wheels' come in many appearances, often together with 'luminous parallel bands' or 'luminous rotating spokes'. Sometimes one, sometimes multiple wheels, rotating clockwise or counter clockwise, with a diameter between 3 and 200 metres, sometimes virtually stretching out to the horizon. At times the spectacle appeared to be under water, sometimes it seemed to be above the surface. Also in this context, 'under water rising and at the surface exploding balls of light' and 'submarine light rays' were observed sometimes together with the 'wheels'. Altogether, a wide-ranging, but very intriguing phenomenon.
To sketch a picture of how a 'phosphorescent wheel' may look, an observation of such an event, reported by the Dutch tanker 'Dione' on 5 November 1978, is given below. This report was published before in the Nautisch Technisch Tijdschrift/De Zee (nr. 4 - 1979), but is detailed to such an extent that it offers a good impression of one of the appearances of such an 'object'. The 'Dione' is one of the 45 Dutch reports of 'phosphorescent wheels' that were received at KNMI since 1910. It is remarkable, that no reports of 'phosphorescent wheels' were received - not even in other countries - from the time that only sailing ships roamed the seas. All reports came from motorized ships. Although bioluminescence (that's what it is all about) was also reported in the age of sail (milky seas and noctiluca scintillans), there was never a report from any sailor of such a dramatic event.
report of 'marine phosphorescent wheels', ms 'Dione'
The observation took place on 5 November 1978 at 00:05 hours, local time on board (4 November 1978, 21:35 GMT). The phenomenon took place in about 15 minutes, after which the wheels and spokes disappeared slowly.
Observation of 'phosphorescent wheels', on board ms 'Dione'
Spokes and wheels rotated approximately one meter above the water, and there where a spoke moved, the sea lightened strongly, about as far outward as the outer wheels. Behind the ship and next to the ship's stern, where the ship lights caused the spokes and wheel to be less, though still clear and recognizable visible, the lighting of the sea was less visible.
The width of the wheels was approximately 1.5-2m, narrower near the centre, but increasingly wider further outward. The spokes, or beams, were cone shaped, pointing at the ship, with the wider part of 2-2.5m outward and curved with a convex shape in the direction of the rotation. The colour of the lighting of the sea was not bright green like one often observes in the Persian Gulf, but fainter white-yellowish; both the wheels and the spokes showed the same colour. The lighting of the sea was visible in patches, nearly circular areas with a diameter of 0.5-1m. The wheels' circles were clearly visible abeam to approximately two ship lengths and forward to about half a ship length (length of ms 'Dione' is 244m).
As mentioned before, concurrently with the large wheel, more, but smaller wheels were clearly visible, with and without spokes (see Figure 1). They were still good visible while the greater wheel was disappearing. Looking at a wheel abeam on portside, it struck me that it didn't have any spokes, and that increasingly growing circles were formed from a certain point, the same that one notices when one throws a stone in the water. There were never more than 3 or 4 circles visible at once and they disappeared without notice. Slowly the wheels disappeared, the large one first, followed by the smaller ones.
further specifications:

- Date and time: 4 November 1978, 21:35 UTC (5 November 1978, 00:05 board time)
- Position: 26°33'.0 N 53°10'.2 E
- Location: Persian Gulf, 8.5 miles NE Stiffle Bank.

- Heading: 121° true
- Speed: 12.5 knots
- No sea or swell
- Calm
- Air temperature: 25°C
- Sea surface temperature: 28°C (engine inlet)
- Height of eye: 18m
- General: clear starry sky, no moon and slightly hazy horizon. Observed many 'falling stars' during the whole evening, of which one appeared to be very near, what was concluded from the long bright green tail that glowed relatively long afterwards.
- Observers: Captain G. Arkema; 2nd Officer J. Boonstra; 3rd Officer J.P. Molenaar; Watchman D.A. Emanuels.

Relation
There is some relation between all phosphorescent wheel reports. Their geographical position is usual in the northerly coastal waters of the Indian Ocean and in the South China Sea, especially at water depths of less than 100 fathoms (about 200m), see Figure below.
Locations of Dutch phosphorescent wheel reports
Interest climate research
In climate research the carbon cycle of the ocean is very important. The ocean absorbs around 1/3 of the anthropogenic CO2 where especially the Coccolithophores play an important role by attaching CO2 to their calcareous skeletons. A study of the distribution, behaviour and phenomena of these luminous algae could possibly contribute to climate research. Coccolithophores are observed especially during their bloom, when they show up as so-called 'milky seas'.
Explanations?
During the years several explanations were given to the 'phosphorescent wheel' phenomena. However, until today none of these explains it completely.
Not much further
All in all there are several explanations from different corners, but no convincing explanation for the complete phenomenon. It seems clear that it is a form of bioluminescence. Especially Coccolithophores and Dinoflagellates are in the picture. The first group, the Coccolithophores, is a type of algae that appears all over the world (except the polar regions) and is visible from space as well in the appearance of 'milky seas'. These areas of bloom overlap the areas where 'phosphorescent wheels' are observed.
compiled by F.B. Koek, KNMI, June 2005