Methane hydrate in the particle accelerator

GLOMAR Paper Award honours first measurement of gas hydrate crystals

Crystals of methane hydrate are up to ten times larger than previously thought, opening future possibilities of dating their formation process. This is what Stephan Klapp, pursuing a PhD at the graduate school GLOMAR - Global change in the marine realm at the University of Bremen, Germany, found when he and colleagues from the University of Göttingen conducted measurements at a particle accelerator at the HASYLAB in Hamburg. For the outstanding publication in the "Geophysical Research Letters" he will be presented with the GLOMAR Paper Award 2007 on Jan 11 2008.

Naturally occurring Gas hydrates crystals measure up to 0.6 millimetres in diameter; laboratory-synthesized hydrates by contrast reach only 0.04 millimetres. “We were truly surprised by our findings – judging from lab-made crystals, we assumed natural crystals to be an order of magnitude smaller”, Stephan Klapp says. “Apparently, hydrate crystals change after their initial formation and continue to grow. One day we may be able to tell the age of methane hydrate with the help of the size of the crystals”, the geologist speculates.

Methane hydrate plays an important role in the global carbon cycle. The quantities of carbon stored as gas hydrate assumed to be lying below the sea floor exceed the carbon in form of oil, gas and coal resources of the planet. At the same, methane is also a greenhouse gas – albeit 30 times more effective than carbon dioxide. This is why it is important to learn more about gas hydrate as a storage capacity for methane. In order to understand how hydrate forms, how it grows and which processes take place in its environment a thorough knowledge of its crystal properties is a prerequisite.

Stephan Klapp and his colleagues used Synchrotron radiation, generated at the particle accelerator DORIS III of the Hamburg Synchrotron laboratory HASYLAB to measure the hydrate crystals. Gas hydrates are only stable at high pressures and low temperatures. To prevent its melting into water and gas, the samples were cooled down to temperatures below minus 200 °C. This also meant that the beams had to penetrate several thick layers of metal – insulation and sample vessels – to be recorded on the other side of the experimental set-up.

“For this, we need high energy x-rays. Just like visible light, x-radiation has a broad spectrum of wavelengths. For instance, the radiation used in clinics has low energy and longer wavelengths”, Klapp explains. “Our radiation here is generated when electrons are accelerated to just below the speed of light. When the electrons are forced by the accelerator to fly in a curve the radiation continues straight ahead – penetrating the side of the accelerator. And it is exactly at this position that we put our samples”, the newly designated laureate continues. The radiation propagates through the sample vessel and sample and is eventually recorded on the far side. From the length of streaks, which the radiation leaves on the detector, the scientists can conclude the size of the crystals.

The Graduate School GLOMAR comprises the four research areas (1) ocean and climate, (2) coastal zone processes, (3) Marine Ecology and Biogeochemistry, and (4) challenges to society. They provide the framework within which the individual PhD students finds the scientific support and training needed to become excellent scientists with a broad interdisciplinary understanding. GLOMAR has been established in November 2006 as part of the German excellence initiative and is financed by the Deutsche Forschungsgemeinschaft (German Research Foundation).

For further information, interviews, pictures please contact:

Name	Phone	Fax	e-mail
Achenbach, Kirsten	+49  421 218 - 65541	+49  421 218 - 65505
Klapp, Stephan A.