November 4, 1995
Location: Latitude = 60 39í south Longitude = 54 11í west
Update:
It has been a busy day on the ship today. After midnight, the OSU team
made test number 8 of the zaps sled looking for hydrothermal vents. This
morning Jay deployed a bottom ocean pressure gage which is used to measure
changes in ocean currents and tides and a variety of other measurements.
This device stays permanently on the ocean floor and has a battery life of
about three years.
The remainder of the day has been spent deploying the new multi channel
seismic streamer. The stream is a device which the scientists use to look
at the construction of the layers of the upper crust of the earth below
the ocean. The streamer is a series of special microphones called
hydrophones. The hydrophones can detect sound waves which are reflected
from the rocks making up the earthís crust. To produce the sound waves
for the hydrophones to detect, the ship towes six air cannons which fire
every twelve seconds. This sound pulse bounces off the different layers
of the earth's crust at different times and the hydrophones detect the
reflected sound. A computer collects the data and averages the data
recorded by the hydrophones and this data is then printed as two
dimensional map of the earthís crust.
For the streamer to work properly it must be towed behind the ship at a
depth of 40 feet. This is not an easy task, because the total length of
the streamer is 1200 meters. The University of Texas science team and the
shipís marine technicians spent a little over 5 hours adding small pieces
of lead to the entire 1200 meter length of the streamer. A total of 200
pounds of lead were added to the length of the streamer. This additional
lead makes the streamer sink just slightly below the surface of the water.
To get the streamer to tow at a depth of 40 feet below the surface they
have to attach special devices called ìbirdsî. These attachments are like
small gliders which fly the streamer in the water. The birds are pressure
sensitive and have two wings like an airplane. The wings adjust up and
down due to the pressure of the water leveling the position of the
streamer to a near constant depth of 40 feet even in high seas.
What made this exciting is that while we were deploying the streamer
the waves grew to about 12 feet, the winds picked up to 20 miles per hour
and it started to snow. It is cold wet work, but it is essential if the
streamer is going to work properly. Everything is checked and double
checked for safety and to make sure everything is in proper working order.
We should start test firing the guns sometime after midnight tonight. The
final attachments will be made to the streamer around 11:00 pm. Everyone
has their fingers crossed. This is the first time that this streamer has
ever been used, and it is the first time that a streamer of this type has
been used in Antarctic waters. A lot of people have a lot of concerns.
The proof will come tomorrow when the computer is started, the air guns
start firing and data begins coming in to the ship.
For the OSU science team it has been a day to review data, plan for
future drops and to make corrections and repairs as needed to their
equipment. They have been getting positive data from their initial
lowering of the sled, and will be making many future lowering to pinpoint
potential areas of hydrothermal vents.
Daily life on the ship is pretty constant. Meals continue to be a
focal point of the day for people to get together. Everyone looks forward
to getting email. The ship connects twice daily with satellite to send
and receive email, once morning and once evening.
