The Major Sampler
The major samplers, or majors, are spring loaded piston fluid samplers that work similar to a syringe. They are good for collecting rapidly flowing black smoker fluid samples, but they are not gastight.
In many cases, they are packaged together in twos attached to a sampling nozzle to go to the seafloor. The nozzle has a temperature probe in it to record the temperature as soon as the sample begins to flow in.
The back of the major. Alvin will pick it up by the handle (skinny metal piece on top) and hold it in place. Before it is tripped to sample, fluid will flow in through the nozzle and out through a hole in the base of the nozzle (not shown). This lets the scientists know that fluid is actually going in to the nozzle and they aren’t sampling seawater. Alvin will then push down the screw, releasing the spring loaded piston, and causing the major to “slurp up” a sample like a large syringe. The red and white cylinder is the temperature recorder.
Here’s one of the two sampling majors. Alvin will push in the screw (right), releasing the pin between the circular piece and the square piece, (very small but visible) causing the piston to come up. Fluid is sucked in through the nozzle and flows into the piston. The major can hold about 750 milliliters of fluid.
The major is then brought to the surface after the dive and opened. The screw in the piece jutting out (right) is turned to release the fluid sample out of the small nozzle attached to it. Again, this is used for sampling black smokers and other high flow areas. The majors are almost useless when studying any diffuse venting sites or trying to do a gas analysis.
The RAS- Remote Automatic Sampler
The RAS is similar to the beast in that it collects many fluid samples at once and that it operates in a similar fashion, with bottles filled with seawater that can be pumped out, creating a vacuum to suck fluid sample into the gas-impermeable bag inside. It also takes the temperature of the fluid as it is being sampled. It is different in that it is able to be programmed to take a sample at a specific time and can be left underwater for an extended period of time. The sampling hose is placed over a diffuse venting site by Alvin and an initial sample is taken by a gas tight sampler. The RAS is programmed to take a sample at a specific time. We recovered a RAS at Endeavour during the first day out at sea that was deployed August 2008 and had been taking a sample every week. We deployed another RAS to the same site that we are going to pick up on the last day at sea. It is taking samples more frequently and is measuring short term changes in the diffuse vent.
The long-term RAS deployments are used to measure a change in temperature and chemical concentration, determine earthquake disturbances, and other changes in subsurface vent systems. It also measures how stable the vent is over time.
The short-term RAS deployments are used to see if any variation in hydrothermal flow exists due to tidal pressure or if the tide influences vent flow rate.
Diffuse vent sites are used as diluted measurements to model how hot vents work. They are also ways to measure what is happening between the deep hot zone and the diffuse sea floor. This can give us clues to what microbes are there, what they are doing, their metabolism, etc.
The RAS- top view. All the blue caps are individual bottles. The system in the center controls when the samples are taken.
A RAS underwater at a sampling site. It looks complicated, but that’s because there are so many bottles and tubes. If you look closely, you can see the reflection of the bags in the outer bottles.
Dave puts a protective plastic shield around the RAS to protect from accidental Alvin arm jabs. It looks like a floating box in the water. It is weighted down with an anchor but is also attached to large yellow floats to make it neutrally buoyant at the seafloor. It is usually dropped at night near where it will be sampling from and then put into place the next day during the dive. It’s rare that anything will be released from the ship while the sub is in the water, just for precautions.
Recovering the RAS: When the ship sends a precise acoustic signal, the RAS knows to drop the anchor and the floats bring it to the surface. If this doesn’t work, Alvin can remove the weights and it will surface.