Variations in ambient light emission from black smokers and flange pools on the Juan de Fuca Ridge

Ambient light emitted by high-temperature black smokers and flange pools on the Juan de Fuca Ridge was imaged using a new spectral imaging camera. Mos t of the light is emitted at long wavelengths (700-1000 nm) and corresponds well to thermal radiation from a body at the same temperature as the vents /flanges. However, black smokers also emit time-varying radiation in the vi sible region (400-650 nm) which cannot be explained by a thermal source. Th is visible radiation is 1-2 orders of magnitude greater than would be expec ted for purely thermal radiation; it exhibits variation with time, despite relatively constant vent temperatures; and it is not associated with the ho ttest part of the plume (i.e. the orifice). Flange pools do not exhibit exc ess visible light over that for a thermal source, suggesting that the light at smokers is caused by mechanisms related to turbulence, mixing, or preci pitation.