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May 5th, 2003; Leg 5, Day #15

We arrived at our dive site early this morning after an all night steam north into a brisk headwind. The first task of the morning was to launch the benthic elevator. The elevator was lowered off the stern of the R/V Western Flyer using the hydrowire. It was released acoustically at about 1,000 meters water depth and allowed to fall downward to the seafloor, which is about 1,400 meters at this site. Much to the relief of the pilots and scientists, the ROV Tiburon passed its pre-dive checkout with flying colors and was in the water before 8:00 a.m. 

Today’s mission was to run a coring transect up the eastern slope of the basin we explored during the previous leg. Six stations were planned, and at each one we were to collect one vibracore, three push cores, and a heat flow probe measurement. All went according to plan until we reached station #2. The manipulator arm spontaneously went through an unexplained contortion and was subsequently unusable. We aborted the dive and recovered the vehicle with the plan to swap manipulator arms. The ROV pit crew swapped arms in record time (below), and we were back in the water in less than an hour. 

 

The ROV pit crew is hard at work in the moonpool, swapping out the manipulator arm. (From left: Mark Talkovic, Buzz Scott, Knute Brekke, and Buck Reynolds.)


We returned to the seafloor, relocated our benthic elevator and continued the coring transect. Along our transect up slope, we encountered outcrops of deformed and tectonically shear mudstones. These outcrops form hard substrates in an otherwise soft-soupy seafloor. The rarity of hard substrates on the seafloor creates a “housing shortage,” and these surfaces were covered with an abundance of invertebrate life—brittlestars, sponges, and crabs (right). We were quite surprised at these outcrops and spent a few extra minutes exploring the area, taking a few push cores before continuing on our transect up slope.
 

Upon arriving at our next sampling location, we proceeded with the routine of heat flow probe measurement, then sediment coring. We loaded two more of the long vibracore samples into the elevator and sent it to the surface, so we would have time to recover it before sunset. 

The new manipulator was working quite well for the pilots, and we had placed a new aluminum tube in the vibracorer to collect another sediment sample. The core easily traveled ~30 centimeters into the soft substrate before stopping, and we continued to vibrate the core into the seafloor. Then another equipment failure occurred. After several minutes of vibrating the core, we were all surprised to see the lifting winch and spool fall from the vibracorer frame! Several minutes of discussion followed as we decided how to recover the partially completed core without damaging either the vehicle or manipulator, as it would be nearly impossible to recover the Tiburon with a half-meter section of the core extending below the toolsled. A series of deft moves by our resourceful pilots enabled us to extract the aluminum core from the frame. The vibracorer was unusable, so the decision was made to abort the dive and recover the vehicle. Despite this second major hardware failure of the day, our dives today were successful because we completed our primary goals for five out of six stations. 

Pete Zerr and Paul Ban spent some time this afternoon towing the benthic elevator back towards the Western Flyer once they found it floating at the surface. It had drifted away from the ship as it rose up through the water, and the ship had moved in the opposite direction. All the vibracores survived the transit and soon the science lab was a blur of activity. These cores and the smaller push cores kept the science party busy until past midnight, while the ROV pilots prepared Tiburon for tomorrow’s mission. 

 

 

 

 

 


At left: Pete Zerr and Paul Ban tow the benthic elevator with the Spare Rhib during recovery operations. At right: Juan-Carlos Herguera, Steve Hallam, Charlie Paull, and Lynne Christianson subsample a push core in the science lab for chemical and microbiological analysis.


The original plan for today was for a long dive and a late night of sample processing, but none of us could have predicted such challenges were awaiting us. To paraphrase Charles Dickens:
 

“It was the best of times, it was the worst of times. It was the ocean of light, and we dove into the darkness. It was the push cores of hope, it was the manipulator of despair.” 

Cheers to all friends and family back home—we miss you! 

Bill Ussler and Peter Walz

As promised in last night’s update, we will reveal the identity of those who posed for the steel-toe trivia photo. From left to right: Peter Walz, Steve Hallam, Pinkie, Bill Ussler, Patrick Mitts, and Ed Peltzer. 

 

 

The science crew drummed up another mystery photo for those of you with inquiring minds. Any guesses as to what this is and who is holding it? The answer will appear tomorrow.

 

 

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