From Douglas Main, OurAmazingPlanet Staff Writer: (http://www.livescience.com/29085-how-brinicles-form.html)What's cooler than being cool? Brine-cold.
When salt-rich water leaks out of sea ice, it sinks into the sea and can occasionally create an eerie finger of ice called a brinicle. New research explains how these strange fingers of ice form and how the salty water within sea ice could have been a prime environment in which life may have evolved.
The study, published in the American Chemical Society's journal Langmuir, suggests that brinicles form in the same way as hydrothermal vents (http://www.livescience.com/26173-hydrothermal-vent-life-origins.html), except in reverse. Hydrothermal vents are spiny-looking towers on the ocean bottom where boiling, chemical-rich water flows out of the seafloor.
The brinicle-forming process goes like this: When sea ice freezes in the Arctic and Antarctic, the salt and other ions in the water is excluded from the water crystals, said study author Bruno Escribano, a researcher at the Basque Center for Applied Mathematics in the Basque Country in northern Spain. This salt-heavy brine accumulates in fractures and compartments within the sea ice (http://www.livescience.com/22651-facts-about-sea-ice.html).
Inevitably, however, sea ice cracks, and the brine leaks out. The brine itself is colder than the freezing point of seawater, since salt-rich water freezes at lower temperatures (hence the reason people put salt on icy sidewalks in the winter, enabling the ice to remain a liquid when it's below freezing), Escribano told OurAmazingPlanet.
Since the concentration of water in the brine is lower than that in the ocean — and water moves from high to low concentrations, via osmosis — water is attracted to the brine. But the brine is so cold that the water freezes, forming a descending tube of ice, Escribano said.
Hydrothermal vents form by an analogous method: Ion-rich hot water is expelled from the seafloor and then begins to dissolve, forming a porous shell of metal extending upward. Water then rushes in, moving from high to low concentration, rupturing the membrane and causing more metal-rich water to spurt out, extending the tube and repeating the process.
Both are examples of "chemical gardens," a type of chemical process and the name of an experiment common in chemistry sets that operates along the same principles and forms tubes of crystals that make plant-like shapes, Escribano said.
Brine-rich compartments within sea ice have some properties that could have helped life originate (http://www.livescience.com/13363-7-theories-origin-life.html), Escribano said. "Inside these compartments inside the ice, you have a high concentration of chemical compounds, and you also have lipids, fats, that coat the inside of the compartment," he said. "These can act as a primitive membrane — one of the conditions necessary for life." They also contain a mixture of acidic and basic components that could provide energy necessary to form more complex molecules, perhaps even DNA, he said.
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. Original article on LiveScience's OurAmazingPlanet.- Album: Stunning Photos of Antarctic Ice (http://www.livescience.com/11259-ice-antarctic.html)
- On Ice: Stunning Images of Canadian Arctic (http://www.livescience.com/13807-canadian-arctic-melting-ice-sea-level.html)
- North vs. South Poles: 10 Wild Differences (http://www.livescience.com/11362-north-south-poles-10-wild-differences.html)
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