*Greenhouse gas to be contained in seabed*

Methane is an important natural gas, but it is also a highly effective greenhouse gas, whose major natural reservoir is marine sediments.

By JUDY SIEGEL-ITZKOVICH
Greenhouse gases (photo credit: REUTERS)
Greenhouse gases
(photo credit: REUTERS)
Ben-Gurion University of the Negev researchers have shed new light on the mechanism that prevents the release of large quantities of the greenhouse gas methane from the sea floor in to the atmosphere.
Dr. Orit Sivan and colleagues from the BGU and the California Institute of Technology and the University of Cambridge recently published their findings in the Proceedings of the National Academy of Sciences (PNAS).
Methane is an important natural gas, but it is also a highly effective greenhouse gas, whose major natural reservoir is marine sediments.
Fortunately, anaerobic oxidation of methane coupled with sulfate reduction has been shown to consume about 90 percent of methane within the subsea floor environment, preventing its release to the atmosphere.
However, the mechanism of this process has remained enigmatic. In this study, Sivan, of BGU’s department of geological and environmental sciences, and her team provided geochemical evidence for the stimulation of this process by iron oxides in methane seep sediments. They proposed a mechanism for the iron involvement. The evidence is based on incubation experiments with seep sediments and measurement of chemical composition and sulfur, oxygen, and carbon isotopes.
SHRINK-WRAPPED SPACESUITS
Spacesuits of the future may resemble a streamlined second skin. For future astronauts, the process of suiting up may go something like this – instead of climbing into a conventional, bulky and gas-pressurized suit, an astronaut may put on lightweight, stretchy garment lined with tiny, muscle-like coils. He or she would then plug in to a spacecraft’s power supply, triggering the coils to contract and essentially shrink-wrap the garment around the body.
The skintight, pressurized suit would not only support the astronaut, but give much more freedom of movement during planetary exploration. To take the suit off, the astronaut would only have to apply modest force, returning the suit to its looser form.
Now researchers at the Massachusetts Institute of Technology are one step closer to engineering such an active, “second-skin” spacesuit.
Aeronautics Prof. Dava Newman, a professor of aeronautics and astronautics and engineering systems at MIT, and her colleagues have engineered active compression garments that incorporate small, spring-like coils that contract in response to heat. The coils are made from a shape-memory alloy – a type of material that “remembers” an engineered shape and, when bent or deformed, can spring back to this shape when heated.
The team incorporated the coils in a tourniquet- like cuff and applied a current to generate heat. At a certain trigger temperature, the coils contract to their “remembered” form, such as a fully coiled spring, tightening the cuff in the process. In subsequent tests, the group found that the pressure produced by the coils equaled that required to fully support an astronaut in space.
“With conventional spacesuits, you’re essentially in a balloon of gas that’s providing you with the necessary one-third of an atmosphere of pressure to keep you alive in the vacuum of space,” said Newman, who has worked for the past decade to design a form-fitting, flexible spacesuit of the future.
“We want to achieve that same pressurization, but through mechanical counterpressure — applying the pressure directly to the skin, thus avoiding the gas pressure altogether. We combine passive elastics with active materials. Ultimately, the big advantage is mobility, and a very lightweight suit for planetary exploration.”
While skintight spacesuits have been proposed in the past, there’s been one persistent design hurdle – how to squeeze in and out of a pressurized suit that’s engineered to be extremely tight. That’s where shape-memory alloys may provide a solution. Such materials contract only when heated and can easily be stretched back to a looser shape when cool. Such equipment may be of use not only in space but also on Earth.