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Raman Spec in the Deep Ocean

IntroductionScreen Shot 2014-12-02 at 7.54.25 PM

Since I am sure that virtually no one outside of academia–and plenty of people within it–will have heard of a Raman Spec before, let’s start there. A Raman Spectrometer is an instrument that directs light onto a sample and then uses the light that returns as its basis of measurement. This is true of nearly all spectrometers [ref]I include this brief caveat since some spectrometers don’t emit their own light and instead use a passive technique, which is much more useful when measuring distant objects like the sun.(citation needed) .[/ref]. A Raman Spec looks for a particular type of light scatter called inelastic, and then the scientist can use that information to infer the sort of molecules involved and the sort of bonding involved. In reference to the oceans, what makes Raman Spec particularly relevant is that the salt water that is inescapable is not an issue when taking measurements [ref]This ability to take measurements from aqueous samples is exquisite compared with the issues faced in taking IR Specs.[/ref].

The Paper

The scientists involved[ref]Pasteris et al. Raman Spectroscopy in the Deep Ocean: Successes and Challenges. Applied Spectroscopy Volume 58, Number 7 (2004).[/ref] in developing one of the first submersible raman spectrometers were interested in being able to take in situ measurements of seawater in close proximity to hydrothermal vent systems. Not only does such a location guarantee great depth [ref]The locations of interest were located approximately 3.6km down.[/ref] but also a sophisticated understanding of the instrument. The species of samples looked at with this system, Doriss as they called it, included:

the mineralogy of the sea floor and the chemistry of pore water, gas seeps, and sea floor vents…[with emphasis on] biologically precipitated solids… biologically produced CaCO3 polymorphs… and the investigation of phosphate minerals (196A).

In their paper, the scientists also describe both their rationale for the instrumentation used as well as their decisions on how to best calibrate and test the instrument. While much of the article dealt with their findings and techniques, it does raise the interesting question of whether such an instrument might prove useful in my own research, a question made more intriguing by the enthusiasm shown by the authors of this paper.

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