Atlantis Diary XI: Encore
The bizarre hydrothermal vent field discovered a little more than two years ago surprised scientists not only with vents that are the tallest ever seen –the one that’s 18 stories dwarfs most vents at other sites by at least 100 feet — but also because the fluids forming these vents are heated by seawater reacting with million-year-old mantle rocks, not by young volcanism. The field is unlike any seen before, according to chief scientist Deborah Kelley , a University of Washington associate professor of oceanography, and co-chief scientist Jeff Karson, a Duke University professor of earth and ocean sciences. Both have visited fields of black-smoker hydrothermal vents that scientists have been studying since the 1970s.
Now the two scientists who were the first to travel in a submersible to the field after its serendipitous discovery Dec. 4, 2000, are leading a National Science Foundation-funded expedition to map and further investigate the field. The ‘Atlantis Diaries’ chronicles the expedition returning with 24 scientists onboard an exploration vessel, the Atlantis, during their 32-day expedition that spanned April 21 to May 22.
This encore series compiles the questions asked to the crew during their expedition, along with their answers about the mission.
Q. What do you expect to learn from the thermal vents?
A. Our challenge is to learn how they formed, whether they have been active for thousands of years, and how their unique chemistry supports life. If we can understand the processes involved, we may gain insights into what vent systems were like when the Earth was very young. Such knowledge may help us search for life on other planets.
Q. How are the fluids and gases at Lost City different from black or white smoker systems?
A. White smokers are chimneys made out of iron, sulfur, lead, and zinc sulfide. They have high temperature (250 to 300°C) plumes of white "smoke" coming out of them. Much of the white smoke is caused by crystallization of fine-grained minerals made out of anhydrite, a mineral composed of calcium and sulphate (SO4). In some of these systems, the sulfide minerals are deposited beneath the seafloor, depleting the fluids in metals. Mixing of these depleted fluids with seawater causes anhydrite to form.
|Away from the hydrothermal vents, there is very little life on the seafloor.Credit: lostcity.washington.edu|
In a black smoker system, the fluids have a low pH and are rich in metals, CO2 and H2S. The black smoker fluids typically discharge at temperatures above 300°C.
In contrast, the fluids at Lost City are clear when they come out of the carbonate towers, and they are much lower in temperature (40 to 70°C). They are also very poor in metals and they do not contain anhydrite. There is more hydrogen and methane in the Lost City fluids and very little CO2 and H2S. In addition, the rocks underneath the Lost City system are altered mantle rocks called serpentinites. The reactions of seawater with the mantle rocks produce high pH fluids with high calcium and near-zero magnesium. When these fluids mix with seawater, calcium carbonate and magnesium hydroxide are deposited. The white carbonate material is what makes up the spectacular structures at Lost City.
Q. Could the vents be polluting the water?
|Ken Rand of the R/V Atlantis heads out to pick up the Alvin divers. Credit: lostcity.washington.edu|
A. The vent fluids from Lost City are certainly expelling gases and chemicals into the ocean water. However, this is a natural process that may have been going on for several thousand years. The plumes emitted from the vents are similar to plumes that form during volcanic eruptions, and also similar to the warm fluids emitted from hot spring systems like Yellowstone. All of these systems contribute chemicals, gases, and energy to their surrounding systems; they are natural processes that have kept our environment in balance for millions of years. Methane and hydrogen are critical to the survival of microorganisms that live in the vents.
Q. What do you look for when you are studying the microorganisms?
A. We look for signs of what kind of metabolism the microbes are utilizing. (Do they eat methane? excrete methane? how about sulfur or hydrogen?) We use three basic strategies to do that: culturing, epifluorescence microscopy, and molecular techniques such as DNA sequencing. For example, we might find that adding methane to culture tubes promotes growth, and that the DNA sequences of these microbes are similar to other microbes with methane metabolisms. We might even find one of the genes that are necessary for growing on methane. There are many different types of metabolism that are likely operating at the Lost City.
|The Beast sampling fluid from a carbonate chimney growing out of a near-vertical wall. Credit: lostcity.washington.edu|
Q. How much does Alvin weigh? How does it float?
A. Alvin weighs about 35,000 pounds. While it seems too heavy to float, there are large blocks of dense foam that make Alvin buoyant in the water. When Alvin is deployed, it carries an extra 960 pounds of weight to make it sink to the seafloor. Air tanks balance that weight until the pilot is ready to take Alvin to the bottom, then the air tanks are flooded with seawater. When the sub reaches the bottom, half of the weight is released so that it can move freely. When ready to end the dive, the pilot releases the rest of the weight and Alvin comes back to the surface.
Q. Given that the unique life forms at Lost City may be sensitive to chemical pollution, do the Alvin ballast weights degrade the environment?
A. The Alvin ballast weights are made out of steel that oxidizes on the seafloor. At Lost City, we enter the area from outside the vent field and drop weights for ballast before we enter the work area. On the way out, the pilots drive away from the field before dropping the final weights. The terrain is very steep in this area and we only have to go 100 to 200 meters away before the slopes drop several hundred meters.
In this way, we do our best to not degrade the environment. However, what we think of as "toxic" to humans is not toxic to many of the organisms that live around venting systems. For example, in black smoker environments there are bacteria that utilize arsenic, mercury, and cobalt during metabolic activity.
Q. How deep do submarines actually go?
|Two swimmers help recover Alvin after a dive. They jump off before it comes aboard. Credit: lostcity.washington.edu|
A. The answer depends upon what submarine you’re talking about. Alvin can go to 4,500 meters, a little more than 14,500 feet. Normally we’ll operate in the neighborhood of 2,500 to 3,000 meters. Other deep ocean research submarines, like the French Nautile and Japanese Shinkai, can go deeper: 6,000 and 6,500 meters respectively. In the past, the deep submersible Trieste made the only manned trip to the deepest part of the ocean: the Marianas Trench in the Pacific near Guam. The Woods Hole Oceanographic Institution is looking into building a deeper diving replacement for the current Alvin.
Q. Do you have to come up slowly in Alvin like scuba divers do to avoid the bends?
A. No, the pressure inside the sphere remains nearly the same as pressure at the surface, so Alvin can come up at about 75 feet per minute.
Q. Have you ever lost an instrument such as ABE or ALVIN during a mission?
A. Debbie Kelley answers: I was on a cruise with the Canadian remotely operated vehicle called ROPOS in the Northeast Pacific Ocean in 1996. A huge storm came up unexpectedly, resulting in 80-mph winds and 20-foot waves developing in a matter of hours. This happened while the vehicle was 7,000 feet below the surface of the ocean. By the time we pulled the vehicle up, nearly the full force of the storm was on us and, unfortunately, the fiber optic cable that connected the vehicle to the ship broke. At nearly the same time, the engines on the ship quit working, and we were not able to maintain visual contact with the vehicle. We searched continually for three days with the help of search planes, but we never found ROPOS. Luckily, there is now a new ROPOS.
Q. How does someone become an Alvin pilot?
A. Pat Hickey, Alvin Expedition Leader, answers: The pilots and technicians who operate and maintain ALVIN are a diverse lot. Some are engineers, while others, like myself, have an enormous amount of experience working in offshore applications such as the Navy and oil fields. When we hire new people, we typically look for someone who has university or college training in mechanics, electronics or electrical systems. A basic knowledge of computer systems is also a plus.
|A view of the sea from the starboard (right side) of the R/V Atlantis.Credit: lostcity.washington.edu|
But all the education in the world can not prepare someone for the extended time we spend at sea. Typically, we spend four months assigned to the ship and then take a two-month vacation. Not bad, hey, four months off every year? But you have to remember that you spend your time at sea with, on average, 55 other people. You share a room and a bathroom, eat with the same people day after day, and when at sea, you can only walk 275 feet in any direction. Things can get "cozy" at times. This is the primary reason that new people don’t stay past their first four months at sea.
On the plus side, the food is excellent, we are in port on average every three weeks, and when we are on vacation, we can live anywhere in the world.
Q. At what temperature does Alvin the submersible stop functioning?
A. You might think that Alvin would have problems in the cold ocean depths, but the submarine operates better when the water temperature gets colder. Average dive water temperatures are around 1 to 4°C. Most of Alvin’s oils and equipment are designed to handle these low temperatures with no noticeable affect on performance.
|Using the submersible’s manipulation arm, Alvin. A successful sample! Careful, don’t drop it. Credit: lostcity.washington.edu|
Only the sub’s batteries are affected by the colder temperatures. Ironically, it’s the warm water that poses the greatest potential for disaster. Water around many deep sea hydrothermal vents can reach temperatures in the neighborhood of 300°C. We’ve even found water with temperatures as high as 380°C in the Juan de Fuca Ridge area. Alvin’s view ports are made of a special acrylic material, and as the outside water temperature rises the view port’s ability to withstand the local water pressure diminishes. Luckily the hot water is very localized and it’s easy to steer clear.
Q. Are you afraid of landslides or small earthquakes while you are doing your study? How do you make sure that you are safe?
A. This is a topic that we really do not discuss much, but it is always in the back of our minds. Scientist do not know many details about earthquakes in the deep oceans, but we do know that there are a lot of relatively small ones. We see evidence of rockslides that were probably triggered by earthquakes on all of the steep slopes. It is possible that the tall, slender spires of the Lost City could topple during an earthquake. So there is always the chance that rocks and other material could come sliding down the cliffs while we are on the seafloor. I am not aware of anyone ever seeing a rockslide from Alvin, but it definitely could happen. There is nothing that can be done to avoid these types of events. Safety is the top priority of the Alvin pilots, though, so they are very cautious about getting close to anything that could be dangerous on the seafloor.
|Sunrise to sleep. The arrival of the sun signifies the end of another work-day.Credit: lostcity.washington.edu|
Q. When do you think the next exploration for new vent fields will be carried out?
A. The French will likely be out here within the next year with their submersible, Nautille. We do not know when we will be able to return because we must submit proposals to the National Science Foundation to get money to return. There are only two times a year (August and February) when we can submit proposals, and it takes about a year or more after a proposal is submitted to get approval. After this, the next stepping stone is finding time on a ship when the submersible or remotely operated vehicle is available. This can mean a one to two year wait because of previous grants that have ship time already scheduled. It is a complicated process, but we are used to it and it just means that we have to plan ahead.
The project includes scientists, engineers and students from the University of Washington, Duke University, Woods Hole Oceanographic Institution, U.S. National Oceanic and Atmospheric Administration, Switzerland’s Institute for Mineralogy and Petrology and Japan’s National Institute of Advanced Industrial Science and Technology. Collaborators include: Jeff Karson, Duke University, Co-PI and diver during the discovery; Matt Schrenk (an astrobiology graduate student at the UW School of Oceanography); P.J. Cimino (a NASA Space grant undergraduate); and John Baross, also a faculty member in astrobiology and oceanography.