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Meteor-Blog 27. July 2008: Gas hydrate - finally!

erstellt von aahke zuletzt verändert: 29.07.2008 15:02

Science is always treasure-seeking as well: David Fischer, PhD student at MARUM-Bremen reports on the joint hunt for the "white gold" of the ocean - gas hydrate - being highly desired due to its enourmous energy capability.

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Does the biodiversity of deep-sea organisms play a role for the climate on Planet Earth? Questions all about marine research will be answered directly aboard of the German research vessel Meteor by cruise leader Prof. Antje Boetius and her crew. In cooperation with the geoportal from 17.07.08 to 24.08.08 they contribute a Science-Blog of METEOR expedition M76/3 GUINECO – MARUM research of fluid and gas seeps on the Westafrican continental margin. Technical highlight of the cruise is the remote-controlled under water robot QUEST4000 by MARUM that will be deployed for taking fauna and sediments samples and conduction of in situ experiments. Go on a dive down to places no other human being has ever seen before: explore the fascinating deep-sea fauna and watch the scientists’ work at gas and fluid seeps deep down on the ocean bottom.

Expedition M76/3b is a collaboration of MARUM – Center for Marine Environmental Sciences at Bremen University and its associated institutes MPI and AWI as well as the French research institute IFREMER and the University of Paris.

More information and an overview of all contributions to the Meteor-Blog and expedition M76/3B:

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27. July 2008 (Author: David Fischer)

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Today's Meteor-Blog is contributed by:

David Fischer“Hello, my name is David Fischer and I am a PhD student at MARUM- Center for Marine Environmental Sciences at the University of Bremen. My work deals with mineralization processes under cold seep conditions. (Picture 1) In other words, I examine the sediment for mineral phases, which form in places where hydrocarbons migrate upwards from deeper sediment layers to near-surface horizons, where they finally get degraded by microorganisms.

27. Juli: shiptrack

Thereby, some geochemical parameters are changed in a way that authigenic mineralization may take place. Our team of four geochemists samples and analyzes sediment cores with various sampling techniques to obtain their pore waters, mineral phases and gas phase components. We concentrate on some local highly active migration pathways off the West African margin.”

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Picture 1: David Fischer in working clothes, ready for the next core

Gas hydrates – finally!

Today I would like to report on a gravity core, which we retrieved from the sea floor in the evening, after a couple of attempts. Upon opening the core liner in the geo laboratory a heavy odour of hydrogen sulphide spread through the whole room and adjacent corridors. This odour - comparable to that of rotten eggs - was the first hint for us that we might have found the sea floor´s “white gold” – gas hydrate. And indeed, at the second glance we found several white concretions of up to three centimeters in length and width, which already started to degrade to gas accompanied by the sizzling sound of burning wood. (Picture 2)

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Picture 2: Burning gas hydrates. Methane ice is quite labile: at surrounding temperatures and lowered ambient pressure it melts rather quickly. (More information about gas hydrates)

But what is the nature of this strange gas hydrate? It is also called methane ice or methane hydrate. It forms in the sediment at greater depth and low temperatures. For example, this location is 4ºC cold and 3200 meter deep, hence the gas hydrates are within their stability zone. As mentioned above, the studied area is characterized by local upward hydrocarbon (e. g. methane) migration. This methane and other associated substances are trapped in distinct subsurface sediment zones. Under in situ conditions it freezes to an ice-like structure, gas hydrates. And really, at first sight gas hydrates resemble water ice. Its particularity is, however, that methane molecules get coated by a film of water. These freeze to solid, cold gas- or methane hydrate.

After the successful core retrieval everybody is looking forward to finding more gas hydrate and probably we will be able to take pictures of it under in situ conditions with our ROV “Quest” – if only Neptune would regards us as worthwhile entering his deep-sea empire!

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Picture 3: Scientists having a sampling flush in the Geolab (Photo by Timo Hansen, one of our motormen on board)