Expedition to the Mariana forearc

Mar. 23 - May 4, 2003

Days 35 & 36, April 26th and 27th

(click on any image for the larger version)

Days 35 & 36

The seas were still rough but had lessened enough to bring Jason to the surface and back aboard. Jason is very near the ship when he is caught on a hook and a crane lifts him aboard. Swells make this part of the procedure difficult, especially today since there was no power to Jason via the tether to Medea. Jason did bump the ship, but fortunately there was no damage to the ship and the damage to Jason was minor.

With Jason back aboard after a 48 hour deployment, the scientists and grad students rushed to collect rocks, push cores and other samples from his collection trays. The benthic tumble weeds in the push core tube went flat after the water drained from the tubes, and they just looked like the sediment.

We picked up transponders and headed south to South Chamorro Seamount. This was the first seamount we visited at the start of the expedition and will be the last.
During the evening a Navy ship in the area changed its course for us after they talked to the R/V Thompson’s Second Officer, Eric. He explained to them that we were on a sonar mapping leg and didn’t want to go off course. The next morning, as we neared South Chamorro, we learned from a Navtex notice (telex system) that we were in a gunnery exercise area. Jake called it a hot zone, the slang term for an exercise using live ammunition. The telex gives the latitude, longitude and radius of the operation. The officer on the bridge plots the information and we can see that we are right in the middle. Chris M. was enjoying the early morning on deck and watched as an Orion P3 anti-submarine warfare surveillance aircraft flew overhead.
Preparing the elevator for deployment Matt H. preparing the elevator for deployment
We arrived at South Chamorro at 0700 and searched for the 2 transponders we had left here over a month ago. Our transponder expert was unable to hear anything from either of the transponders. We all have ideas about what has happened: the logical—the transponders have quit sending signals, the exotic—giant squid in action, the mysterious—military decoding and target practice. We hope that they are still here and we can later signal their release and find them at the surface. Each transponder is worth about $10,000.
CORK (Circulation obviation Retrofit Kit) in the top of the drill hole CORK (Circulation Obviation Retrofit Kit) in the top of the drill hole

We could not deploy new transponders because we were out of wire to tether them to the seafloor. We solved the navigation problem by putting transponders on 2 pieces of equipment that we sent to the seafloor before launching Jason. The 2 pieces of equipment were a dummy logger and an elevator.

A week before the official start of this expedition (6 weeks ago), we went to South Chamorro with Jason and visited the site of an ODP drill hole (Ocean Drilling Project). The hole, drilled in 2001, is 202 meters deep into the seafloor and lined with steel pipe. It was topped with a CORK (Circulation Obviation Retrofit Kit). Inside the drill pipe were a data logger and Osmo Sampler. The data logger had been recording temperature and pressure for 2 years. Our first visit, 6 weeks ago, was to get the data logger and Osmo Sampler. Michelle was able to get the data from the hole by “plugging-in” electronically, before the data logger was actually removed.

Precipitates flowing from the top of the CORK Precipitates flowing from the top of the CORK (Jason's manipulator and storage box can be seen on the right)

Geoff put the Osmo Sampler in the pipe two years ago to take water samples. It works by osmosis when very salty water at one end “pulls” the less salty water in the drill pipe across a membrane and up into very thin tubing. The thin tubing is miles long and can slowly gather water for several years. When the tubing is removed and cut into sections, the chemist can analyze the water as it was collected week by week. When the data logger and Osmo Sampler were removed 6 weeks ago, we could see active flow from the drill pipe so the top was left open for today’s visit.

Jason’s light bar and tether were repaired and Jason was launched just before dinner. With transponders on the dummy logger and the elevator, Jason was able to locate the drill hole within a few hours. The active flow from the drill pipe was reacting with the seawater and the precipitation was highly visible. The precipitates had started to build a chimney at the top of the drill pipe. The chimney was snowy white and built of beautiful crystal formations. We took water samples, temperature measurements and tried to get samples of the delicate crystals. The dummy logger (looks like the data logger but doesn’t collect data) will be used to seal the drill pipe so it can be used in future studies.

 

Science Summary - Days 35 and 36, April 26th and 27th

Science Objectives, Day 35:

The thirty-fifth the cruise, Apr. 26, we will finish a bathymetric survey while transiting south for S. Chamorro Seamount and arrive at the site for deploying equipment and an elevator at the seamount at about 0700 local time. We plan to launch Jason2 in the morning and will use it to place a dummy logger in the borehole at ODP Hole 1200C and to recover flow meters deployed in the vicinity of ODP Hole 1200A. We will also take temperature measurements in the borehole, and take water samples from it. We will then collect push cores and rock samples. The flow meters will be recovered using an elevator.

Science Objectives, Day 36:

The thirty-sixth day of the cruise, Apr. 27 , we will complete work at S. Chamorro Seamount, recover the vehicle and then commence a bathymetric survey toward the southwest.

Return to the Daily Update Page