Keck Expedition 2004
August 24, 2004 Day 10

Cruise log as of 1800 August 24,2004

Peter Girguis, acting chief scientist

Well I can honestly say that our cruise has been remarkably successful and, as a consequence, extremely busy so I’ll start by summarizing our expedition to date. As you may have gathered from prior reports, we spent the first four dives in the Mothra and Main Endeavour vent fields. During these expeditions, we sampled high temperature flows from several different hydrothermal vent structures, collected fragments of hydrothermal vent chimneys, collected water from above diffuse vents, and completed transects to confirm high resolution maps made using acoustic instruments on prior cruises. Afterwards, we spent half a dive at a field called sasquatch. Like its namesake, this field can be difficult to find. However, the sasquatch vents were unable to hide from the keen eyes of our pilots, who found the site in no time (note: they did have some help from our colleagues who have produced exquisite maps of this area). In any case, this was also a wonderful dive because this field has an interesting structure. It sticks out of the seafloor like an artificial reef. skate.jpg (155203 bytes)Fish, like this skate, seem to be attracted to it (Do you think he's looking for a meal?). It also gave us the opportunity to leave a marker at the site. This is a service to the scientific community because it allows us to find the same sites easily without having to waste precious time by flying around and trying to identify the vents by landmarks. We came up with a marker that is really quite distinct; one that I believe clearly designates the site. pinkie.jpg (145614 bytes)What do you think? I for one look forward to visiting Pinkie the Flamingo when we revisit this site in 2005 or 2006.

After visiting sasquatch and collecting a few water and rock samples for geological, chemical and microbiological analyses, we spent two days in middle valley, visiting sedimented vent sites that have not been visited in many years. You can read all about them in the prior web update.

Today was the seventh dive day of our expedition, and we returned to the Mothra vent field instead of visiting the Nootka seep site (some nasty weather was headed our way and we were quite interested in avoiding it). The return visit was quite useful as it allowed us to verify our prior navigational data. On the seafloor, you can’t use high-tech positioning systems like GPS because the signal cannot penetrate water, and compasses will only get you so far. As such, we have to use sophisticated computer programs to track the position of the ship and the ROV relative to the seafloor. It gets messy at times, and we like to verify our position by visiting something we recognize (such as that marker I mentioned earlier). In addition to flying around and verifying our navigation, we spent some time collecting more water samples to help us better understand microbial distribution and abundance. In particular, these water samples should help MBARI scientists in developing molecular probes that will allow us to track the occurrence of these microbes in real time using seafloor instruments such as the environmental sample processor, or ESP (see MBARI website for more details). In any case, it was exhilarating to visit Mothra again and see those spindly sulfides rising up from the seafloor. Some of them are several stories high, such as this chimney in the Mothra field.

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