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Logbook
June 26, 1999

Contents:

• News from Thompson
• News from Wecoma
• Participant Perspective
• Logbook from Teacher at Sea
• Question/Answer from shore to sea

Science Report - Saturday, June 26
Ships Location: 45 55.9/129 59.0

Deployment of the range meter for calibrating the transponders used for ROV navigation underwater.

We had more problems with hydraulic leaks on ROPOS dive 487, early this morning, but the ROPOS engineers are now confident they have found and corrected the problem. One of the lines that drained the hydraulic system was kinked and so pressure would build up and rupture seals elsewhere in the system. Before today, they were only correcting those ruptures, but not the underlying cause. ROPOS is now on its way down for dive 488, and hopefully will get to stay down as long as we want it to this time. While ROPOS was on deck today we calibrated the navigation transponders we deployed yesterday, which is the process you have to go through in order to precisely locate them on the seafloor before you can use them for navigation. On this dive, well be trying to visit some of the other vent sites on the 1998 lava flow that we saw last summer to collect vent fluid samples, biological samples, recover OSMO samplers, and collect more Imagenex sonar data to expand our high-resolution map of the lava flow. Our hopes are high for a long and productive dive.

See Wecoma's teacher log for information.

Listing of all Science News postings

Thomas Chapin

Monterey Bay Aquarium Research Institure (MBARI)

Hi. I'm Thomas Chapin, a scientist from the Monterey Bay Aquarium Research Institute (MBARI, www.mbari.org). I work at MBARI with Hans Jannasch, Geoff Wheat, and Ken Johnson developing long term underwater samplers (Osmo Samplers) and chemical analyzers (Osmo Analyzers) for monitoring hydrothermal vents. Scientists have been able to get out to the Juan de Fuca ridge fairly often and have begun to develop some theories on the chemical evolution of hydrothermal systems from eruption to when the vents die out. However, the chemical sampling has mostly been accomplished with ships and ROVs which, if you're lucky, get out here once or twice a year for a few weeks. That's like only seeing 10 minutes of a 2 hour movie; you get some idea of the plot but you're making educated guesses about what happened before you got there or what happens after you leave. That's where the MBARI folks come in, we put down Osmo Samplers and Osmo Analyzers that continuously collect samples and data for up to a year.

There are many potential problems with long term continuous samplers and analyzers including limited power, fouling of intakes, moving parts wearing out, etc. To overcome some of these major problems, we use osmotic pumps. These are pumps, which rely on osmosis, the principle that water will cross a semi-permeable membrane to try and balance outs the salt concentration on both sides. Since you have water moving from one side of the membrane to the other, you are effectively pumping it, and we can employ this idea to move samples and reagents. The coolest thing about the osmotic pump is that it requires no electrical power to move water! It also moves water very slowly, about 0.25 ml/day. Osmo Samplers continuously pull the hydrothermal water into a really long (>200m) coil of tubing. After a year, we pick up the Osmo Sampler and cut the tubing up, each meter of tubing is about 2 days worth of sample. So the Osmo Sampler requires no electricity and just sucks sample into a long coil of tubing. On the other hand, the Osmo Analyzer is an instrument, which does require some battery power to continuously measure iron (Fe) concentrations in hydrothermal vents. Osmotic pumps are used to add reagents to the sample to make a colored compound. The color intensity, which is proportional to the Fe concentration, is then measured every 30 minutes. A data logger and battery pack provides the program and power to run the electronics. I'll be recovering two Osmo Samplers, which were deployed last year and bring them back to lab for analysis. This data will be incredible since we'll be able to see changes in hydrothermal chemistry over the entire year with almost a daily resolution. For this cruise, I will be deploying four Osmo Samplers and two Fe Osmo Analyzers, which will be picked up next year.

Listing of all Perspectives postings

Wecoma Teacher at Sea Log

Day 11, Saturday 6/26/99

Our day was filled with a long tow-yo deployment along the Cleft segment. The sawtooth pattern of our tow was marked on the large chart on the lab's map table. More samples were collected for chemical analysis and interpretation.

Ron Greene, Research Assistant OSU/CIMRS uncoils shiny copper tubing on the floor of the dry lab. He then carefully measures and cuts the tubing into 2 ft lengths. Each tube is capped at both ends to keep them dust free. The scientists later attach clear aquarium-type tubing to drain sea water from the Niskin Bottles when the rosette returns from the deep. Bubbles are removed by pounding on the tubing with a small metal rod. I enjoy watching the scientists for it is as if they are playing a percussion instrument in an orchestra. Ron explains that gases from the earth's mantle enriches the hydrothermal plume signal with both 3He and 4He (Helium). Both are stable isotopes with 4He being 1,000,000 times more abundant than 3He. The seawater holds many answers to questions scientists ask. After collecting seawater into copper tubing, the dissolved gases are later removed at the PMEL laboratory in Newport, Oregon. Helium gas is conservative and inert and only affected by dilution from the vent site onward. It does not decay nor react chemically or biologically with other elements. It is an ideal tracer. In the Newport laboratory the collected seawater is analyzed with a sensitive mass spectrometer to isolate helium from the other gases. The 3He and 4He atoms are counted and information of this important element in the Western Pacific is completed.

The meals served aboard the Wecoma have been more than wonderful. The food is served cafeteria style with a menu posted on the bulletin board before each meal. Doug Capps, cook, and Lee Helton, messman, have provided us with a wide variety of culinary delights. We all enjoyed the fare this evening. Salad bar with prawns, Soup of the day: Chicken noodle. Fillet Mignon, New Zealand Rack of Lamb, baked Yams, green peas with proscuitto and onions, fresh baked rolls followed by desert: chocolate mousse. With meals like this I'd call Doug and Lee top class Chefs!

Have you eaten all your vegetables? To be a scientist it is important to be of strong mind and body.

Fair seas,
Ms. Deck

Thompson Teacher at Sea Log

Teacher Log #6 6/26/99

My day started as usual by throwing on some warm clothes (its chilly out here) and stepping out onto the weather deck (there is a reason they call it that) to check the weather. I start my observation with a view of the water. From that first look I can determine whether or not were moving for one thing, but it helps me determine what the sky and wind conditions are. Like all the other mornings, the water was gray (cloudy sky) and choppy with a few white caps (moderately windy - 10 to 15 mph). We have had decent weather (Im told that it could be a lot worse). Almost every day we have been getting a break in the clouds where the sun is shinning and the breeze picks up. It is always nice to see blue ocean water. Keep your fingers crossed and say a few kind words, so that our nice weather holds (it is not possible to use ROPOS in rough water).

Leigh Evans working on the vacuum extraction system for getting samples of helium from ROV samples on board the Thompson.

One of the first people I met on board when I arrived in Victoria was Leigh Evans from Oregon State University/NOAA-Vents Program. In our conversation (remember me as the reporter out here) we talked about his work on this particular cruise. He is going to extract gas from the vent fluid. His particular focus is on how much Helium 3 isotope is present. Helium 3 is of interest because it is degassed from mid-ocean ridge magmas and because it is conservative (it doesnt react chemically with other elements). Therefore it is an excellent tracer of hydrothermal plumes and how much interaction they have had with erupted lava. To extract gases Leigh uses an elaborate "sea going vacuum system" (left). The first thing you must be aware of is that air has an abundance of elements in it, especially helium (about 100 times more then in sea water). For this reason, the first step in preparing his vacuum system is to flush the machinery of air. Air is pumped from the system to clear the lines and containers. He then adds the vent fluid collected in "Gas Tight Bottles" and it flows down into a collecting flask that has powdered acid. The acid helps to drive the vent fluid to equilibrium so that carbon dioxide gas is created and other gases in the sample are released. From there the gas escapes the fluid and rises up and into a collecting tube that leads to a condensing container. As the gas enters this container with a temperature of between negative 50-60 degrees C, any water vapor within the gas mixture separates out. Gases are then moved along into another container which allows the volume to change and can be mechanically controlled. Gases are then moved to a collecting valve where they are sealed for analysis at a later time. Once you have a known volume of gas along with the temperature and pressure it is collected under, the actual amount (in moles or cc @ STP) can be determined.

Question for all you chemistry students out there:

What equation would allow you to calculate the amount of gas collected in the process above?
Check tomorrow for the answer.

One of the ways that Leigh can check to see what percent of his sample came from the vent fluid versus the sea water surrounding it, is to determine how much Magnesium is in the fluid left over from the separation process. Pure vent water will have no Magnesium, while seawater normally has around 50 ppm (parts per million).

One of the more important pieces of equipment that never gets mentioned is the winch (right) used to lower and raise ROPOS into and out of the water. It is so large it takes one entire triple axle tractor trailer to transport. It weighs over 64,500 pounds. The major component of the load it carries when ROPOS is in the water is the cable (which is 3500 meters in length). The more cable that is paid out in deployment of the ROV, the greater the load. The cage, which normally is stationed about 30-50 m above the sea floor, also has a winch that is responsible for recollecting the tether which attaches ROPOS to its cage (no more than 150 meters) and does not have a load responsibility due to the neutral buoyancy of ROPOS.

ROPOS is geared up for another dive, the crew is optimistic of great successes to come. Keep following the action. Bye for now.

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