 Leg 1 Logbook - Laser Raman Spectroscopy
Day 13 – Keith, you’re going to need a bigger dive bag!
July 19, 2009 On station at Barkley Canyon, 40 nautical miles southwest of Vancouver Island, Canada. This is our last dive at Barkley Canyon. Most of the tasks that we set out to do have been completed, most of the measurements have been made, and only a few tasks remain so we looked forward to a short dive and an easy day. First on our list was a desire to get one or two more oil samples. With a short list for the day, we knew we could spend almost as much time on this task as we wanted. Arriving on the seafloor, we transited to the “Mount St. Helens” mound. As we set down on the edge of the mound the weight of the vehicle began forcing a steady stream of oil droplets out of the mud. It was all we could do to get the sampling funnel over the stream before it ran out. Much to our delight, within a few short minutes the sampling chamber was full and we collected the sample. Since that one went so easy we decided to try and get one more at the extreme southern mound, “Cliff Hanger.” Unfortunately, we had already found our “big gusher” for the day and try as we might, there was little oil to be found at the second site. Then, abruptly, the handle broke off the funnel as we attempted to use it to root around in the mud to find more oil. Obviously, we were now done with that task for the day, so we stowed what remained of the sampling funnel in one of the baskets on the toolsled tray and collected a push core instead. Perhaps there will be enough oil in that mud to make up for the lost sample. 
Collecting our last push core at the “Cliff Hanger” mound where little oil was found. However, when we inserted the push core, a burst of droplets appeared.
At this point, we were way ahead of schedule, so we transited to the northernmost mound in search of solid hydrate. Along the way we stopped at “Cliff Hanger” and straightened up the stakes that had gotten inadvertently knocked over earlier in the day. Keith Hester had rigged a dive bag inside one of our sampling rings hoping to be able to maneuver a piece of hydrate about the size of a loaf of bread inside. Once inside, we could then use the manipulator arm to pull the string tight and trap the hydrate securely within. Approaching the mound we remembered seeing several slabs of hydrate sticking out along the rim the day before and hopefully we could break off one of these and catch it in the dive bag. As we set up for the procedure, one of the pilots got the idea that we could pry the hydrate loose using the benthic hoe. Sure enough, this worked, but then we got a big surprise: the slab of hydrate that we released was two-to-three times the size of the sampling ring, and no way would it fit inside the dive bag! Undaunted, we tried to capture it anyway, until it was very clear that we really did need a much larger bag to contain it! 
Tidying-up the dive site, ROV Doc Ricketts sets the markers straight again after knocking them over earlier in the day. These markers will remain on site to give a visual reference point for all future visitors. 
Using the benthic hoe, the ROV pilots pry a large slab of yellow gas hydrate loose from the seafloor. We immediately realize that we are going to need a bigger dive bag to collect this sample. Fortunately, it was at this point that the hydrate slab broke into pieces. Several got away immediately, but the pilots did manage to capture one of the larger ones inside the bag. Realizing it was going to be a bit tricky to keep under control during the ascent, we abandoned the plan to tuck the sample in one of the sampling box and instead used one of the manipulator arms to pin the ring on top of the milk crate on the ROV's front porch. With our major find secure, we headed for the surface. Along the way, we heard from the bridge that several pieces of hydrate had popped-up at the sea surface just in front of the ship. They quickly maneuvered into position and Peter Walz scooped them up with a net. So, apparently, today one can loose their hydrate and get it back! Meanwhile, back on the ROV, we had a spectacular display of hydrate dissociation during the ascent to the surface. 
Gas hydrates are only stable at the low temperature and high pressure conditions found on the seafloor. When the samples are brought unprotected to the surface, they decompose spontaneously releasing large volumes of methane gas. Once on-board, we spirited the hydrate to the back deck where it was broken into small pieces and set it on fire: this ice really does burn! —Ed Peltzer 
When lit, this “ice” really burns. Methane gas is the primary component of these clathrate hydrate specimens along with ethane, propane, butane, and other low molecular weight hydrocarbons. As they decompose they release a flammable mixture of gases and fresh water. 
A horde of happy hydrate hunters on the back deck of the R/V Western Flyer.
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Track the ship
Equipment
 R/V Western FlyerThe R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
By bouncing a specially tuned laser beam off of almost any object or substance—solid, liquid, or gas—a laser Raman spectrometer can provide information about that object's chemical composition and molecular structure.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using ROV Tiburon's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.
Carbon dioxide is a liquid at the temperatures and pressures on the seafloor where hydrates are known to occur. Because of this, one cannot simply take down a tank of gas and expect to be able to release it at depth. Instead, the CO2 piston accumulator is used to deliver precise volumes of liquid CO,2 to experiments on the seafloor. The valves are operated hydraulically by remote control and hydraulic pressure is used to expel the liquid CO2 and deliver it to the experiments.
MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path. The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean. Research Team
Peter has taken part in more than 30 deep-sea cruises, and has served as chief scientist on major expeditions and on more than 90 ROV dives with MBARI ships and vehicles. His research interests include the ocean geochemistry of the greenhouse gases. He has devised novel techniques both for measurement and for extracting the oceanic signatures of global change. At MBARI his current interests include the geochemistry of gas hydrates, and the evolution of the oceanic fossil fuel CO2 signal. He has developed novel techniques for deep ocean laser Raman spectroscopy, and for testing the principles and impacts of deep ocean CO2 injection.
Ed is an ocean chemist who has been with MBARI since 1997. He has been involved in developing instrumentation and analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has also collaborated on the development of new instrumentation for the measurement of temperature and pH from an ROV. As the group's project manager, Ed is also responsible for expedition planning and logistics.
Peter has worked as a research technician for a variety of scientists at MBARI. Most recently he has supported the research efforts of Dr. Peter Brewer and his interests in the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter assists with the design, testing and deployment of the ocean going science hardware and works closely with the marine operations group to integrate new equipment to work with MBARI's ROV's.
Xin Zhang is a Ph.D. student from the Ocean University of China and is now studying at MBARI with Peter Brewer and Bill Kirkwood. He has been involved in the development of a Deep-Sea Raman Probe for the measurement of sediment pore water geochemistry. In this expedition, he will focus on obtaining the in situ pore water Raman spectra and the collection of pore water samples for subsequent shipboard analyses by ion and gas chromatography.
Keith is currently an associate engineer with ConocoPhillips focused on natural gas hydrates. Keith received his PhD in Chemical Engineering from the Colorado School of Mines in 2007. This was followed by a two-year postdoctoral fellowship at the Monterey Bay Aquarium Research Institute with Dr. Peter Brewer. His research interests include the use of carbon dioxide to replace methane in natural hydrates.
John has been a staff member at the NRC since 1974, first with the Division of Chemistry, then with the Steacie Institute for Molecular Sciences upon its establishment in 1991. His research focuses on the chemical applications of solid state nuclear magnetic resonance (NMR) spectroscopy, the development of multi-technique approaches to the characterization of materials, supramolecular chemistry, porous materials, clathrates, gas hydrates, and other guest-host materials. He has nearly 500 publications and six patents and is often an invited speaker at special events. |
