DEEP OCEAN

Raman spectrometers tell scientists what almost any substance - solid, liquid or gas - is made of, eg. paint pigments on ancient temples on land but it also goes well under water.
The spectrometer works by focusing a laser on a target object. Most of the beam scatters off the object at the same wavelength as the laser. A small part of the beam (one in 100,000,000 photons) interacts with the chemical bonds of the molecules inside the target area and scatters at different wavelengths. Reading these wavelengths scientists can distinguish the composition of any samples collected.

Sheri White has helped develop the Deep-Ocean Laser Raman In-Situ Spectrometer (DORISS). This is a precision laboratory instrument in a pressure-proof container designed to work on the seafloor where many materials exist only in unusual conditions and can't be brought to the surface to study. She had already helped build and test ALISS (Ambient Light Imaging and Spectral System) to measure the light emanating from hydrothermal vents on the ocean floor. White was able to determine that the energy from this vent glow came from thermal radiation produced by extremely high-temperature (approx 350 degrees C) vent fluids.

A major problem with DORISS is the fact that spectrometers only see the precise point where their laser beam focuses, an area smaller than a pinhead and then it has to be held absolutely still for minutes at a time, something impossible to do from a ship at sea level to a ROV aat the end of a 4,000 metre tether on the ocean floor. White's answer was to build a 3-legged lab bench - Precision Underwater Positioner (PUP). This device complete with rigid legs, camera, light and crossing lasers helps to position the laser probe precisely and stably on the small targets in the deep ocean.

Chip Brier is a postdoctoral fellow who developed the Suspended Particulate Rosette (SuPR) to collect samples from the deep ocean vents. SuPR can collect 24 separate 100 litre samples where other samplers collect a single 2,000 litre one.

White and Brier are working to integrate a raman spectrometer into the SuPR for a trial run through a hydrothermal vent plume effectively analysing the chemical and trace elements as they emerge before combining and transforming as they interact with sea water. Then by taking a succession of samples they hope to record what happens as the chemicals and particles (eg. iron, manganese) interact with sea water elements (eg. vanadium, chromium) forming new minerals.