Logbook
September 17, 1998
Contents:
Today's Science News
Participant Perspective
Logbook from Teacher at Sea
Question/Answer from shore to sea
Not available.
Listing of all Science News postings
My name is
Jim Gendron. I am an oceanographer with
NOAA's Pacific Marine
Environmental Lab in Seattle. My main interest is the 'smoke' that forms
above the hydrothermal sources. This hydrothermal particulate is composed
of very small grains of material that precipitate rapidly after leaving
the vent. As the particles form they become the characteristic rising plume
that you see. Just like smoke from a smokestack, this plume can ascend up
to 200 meters from it's source.
How do you detect such a plume?
One of the instruments on the CTD is called a nephelometer. It shines a
light into the water and then detects any light that is scattered back to
it's sensor. The brighter the returning light signal is, the more particles
there are.
How do you collect samples of the particles?
Samples can be collected using the Niskin bottles on the CTD (gray, tubular items in photo on left), or by mounting
Niskins directly on ROPOS. The fluid sampler on ROPOS can also be used to
filter the plumes in place. In all cases the samples are filtered onto
plastic membrane filters. Then they are dried and kept under a vacuum until
they are brought back to the lab in Seattle.
How do you analyze the samples?
Each sample is placed in a instrument that blasts it with X-rays. The sample
will then give off new X-rays that can be used to tell what elements are
present and how much of each element is in the sample.
What elements do you find in the 'smoke'?
The most important elements are iron, sulfur, zinc, copper, silica, manganese
and phosphorus. The orange-brown color that you can see in much of the
sediment cover on the basalt is probably due to iron.
Consider the following:
These hydrothermal vent systems were not discovered until after humans had
walked on the moon.
Listing of all Perspectives postings
September 17 - 1100 hours
If there was any doubt that fall is just around the corner is was dispelled last
night.. Those squalls that blew the ship off station yesterday turned into
winds that peaked over 30 knots, and the confused sea-state made it impossible
to get ROPOS back in the water. It also made sleeping in an upper bunk in the
forward part of the ship a hit-and-miss affair. ROPOS is still on the aft deck.
Bob Embley and the ROPOS technicians are meeting out there trying to decide
whether or not to try for a launch. We have apparently reached the center of
this low pressure and, like the eye of a hurricane, things have temporarily
calmed down. Of course as we come back out the other side we can expect
increasing winds, but from the other direction. That may actually help to knock
down some of the seas that are keeping ROPOS on the deck.
There are two dangers in launching ROPOS in marginal conditions. Of course the
first is that with the ship lurching back and forth there is always the chance
of slamming the sub against the ship. The second danger comes from what is know
as a "snap load". This is the tension that is applied to the tether when the
cage is suddenly pulled up and down violently by the action of the ship. It is
usually during the extreme tension of a snap load that something gets separated
in the tether. This could potentially lead to anything from another major
retermination to loss of the sub. No one wants to take a chance on either of
those. A full retermination would probably end the expedition right here since
there would be little or no time left after repairs.
At the very least
scientists want the
extensometers in place and
other bacteria traps and
temperature probes back on the ship. So for now we watch the weather computer
screens and wait for an opening. I go on watch at 1200 hours. It will either
be four hours of thumb-twiddling, or a hectic race to beat the weather. More
later.
2030 hrs
We have been high and dry all day. The barometer has dropped, winds have been
steady at better than ten knots and the pilots don't like the look of the
current swell, so we are in a holding pattern, hoping to get in at least one
more dive before we break camp. Regardless of weather or work undone, we depart
for Victoria at 0400 hours on Saturday morning, so if the last dives happen it
will be later tonight and again tomorrow.
There is not much else to report tonight. The scientists are beginning to work
on their summaries for the cruise log that will be published soon. Their
homework assignment, and mine, is to have the summary written and submitted to
the chief scientist before we land in Victoria. Other than that the big news on
board is that the cribbage tournament was won by someone who spent a good deal
of his freshman year at the University of Washington playing cards when he
should have been studying. That would be yours truly.
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