Deep beneath the oceans, continental plates grind together. Sea water seeps into the ocean floor, contacts superheated rock and roars back out through hydrothermal vents. Surrounding those vents, darkness, pressure, poison gas and heavy metal, acidity and temperatures ranging from freezing to hot enough to melt lead create a zone that would instantly kill most forms of life on this planet–and yet, life thrives there.
It’s so difficult to reach these regions of the ocean floor that we know very little about them. But we’re about to learn more. Just a few days ago, a remote-controlled Canadian robot called ROPOS (Remotely Operated Platform for Ocean Science) descended 2,500 metres to the bottom of the Juan de Fuca Ridge, 320 kilometres off the Pacific Coast. Using a diamond-studded chainsaw, ROPOS cut a three-metre sample off of a “black smoker,” which was then hauled to the surface.
Black smokers form where hot water, laden with sulfide particles, belches out of a hydrothermal vent. Raining down around the vent, the particles form an ever-growing chimney of stone, from whose tip water continues to roar out, looking like black smoke.
When hydrothermal vents were first explored in 1977, scientists were shocked to discover life all around them. No one thought life was possible in the absence of sunlight, but scientists found mussels, clams, crabs and tubeworms in abundance.
The key to this unexpected profusion of life is bacteria that thrive on hydrogen sulfide, one of the primary ingredients of the black smokers’ “smoke.” These bacteria provide nutrients for creatures higher up the food chain, such as mollusks, which eat the bacteria directly, and tubeworms, with whom they live in symbiosis: the bacteria live in the tubeworms’ tissues and the tubeworms use the organic compounds the bacteria produce.
Darkness is just one challenge to life at the vents. The bacteria may thrive on hydrogen sulfide, but it’s a deadly poison to most other forms of life. So are the heavy metals that pour out of the vents. The vent water is also more acidic than vinegar, to the point where it dissolves snails’ shells before they can form. Then there’s the pressure (roughly 235 kilograms per square centimetre at 2,500 metres) and the extremes of temperature: just above freezing all around the vents, 400 degrees where the water roars out.
Dr. John R. Delaney, a oceanographer from the University of Washington, has been fascinated by black smokers since he first saw one 14 years ago. It was his idea to try to bring one to the surface. Even though the life forms attached to it would die almost immediately, biologists could examine them the moment the smoker was on deck, and geologists could study the smoker itself.
He put together the current expedition, which includes of the Canadian Coast Guard Ship John P. Tully and the oceanographic research vessel Thomas G. Thompson, with funding from the University of Washington and the American Museum of Natural History.
Last Saturday afternoon, the refrigerator-sized ROPOS descended to the Mothra hydrothermal field, piloted by Keith Shepherd, General Manager of the Canadian Scientific Submersible Facility. On a previous dive, the researchers had pre-selected a black smoker, nicknamed Phang.
After having carefully examined and photographed Phang for before-and-after studies, Shepherd cinched wire loops tightly around it, attached to a cable leading up to a 13,600-kilogram winch on the John P. Tully. Then he began cutting.
Before he was through, the chainsaw gave out. Fortunately, he’d cut deeply enough that the Tully’s winch was able to break Phang free and haul it to the surface. There had been fears the black smoker might break apart, but the recovery went smoothly.
Already scientists are studying Phang, as well as monitoring the ocean floor to see if Phang’s stump will immediately begin to regrow, and if wildlife will recolonize it.
Hydrothermal vent systems are important to study because they’ve probably existed on Earth almost from the time the ocean formed. (In fact, some people believe the first life forms appeared around hydrothermal vents.) Studying them can give us insights into the development of life on this planet, and possibly even other planets: Jupiter’s moon Europa, for example, appears to have an underground ocean, as well as volcanic activity. That could mean that beneath the ice of that frozen world, life thrives around hydrothermal vents just as it does here.
Ironically, we may learn the secrets of life on other worlds right here in the inner spaces of our own.
