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Lost City Expedition: Science

How do You Sample the Gases Dissolved in Vent Fluids?

One of the most interesting processes to watch onboard this cruise, will be the extraction of gases from the hydrothermal vent fluids using a glass gas extraction line. Gases in the vent fluids may come from alteration of the rocks, degassing of magma chambers, or as by products of microbes. Gases “leak” through many types of containers, and even within the titanium samplers, microbes may “eat” the gases before we can analyze them.

On board the ship we must extract all the gas from the fluids sampled using Gas Tight Samplers. This is a fairly long process, taking about 1.5 hours per sample, but can always take longer due to unexpected problems. Once the gas is extracted we dry the gas (removing the water vapor) using a cold trap and package the gas into little “breakseal” glass vials. These vials are then carefully wrapped so they can be taken back to shore where, in addition to stable and radiocarbon isotope analysis, they are measured for chemical composition, helium content, and archived for any other measurement that may be required in the future. The attached picture shows a schematic of the seagoing extraction line. The sample in the gas tight is loaded on the left, and the extracted gas is sealed in the vial on the right.