Brewer Expedition
August 10 - August 17, 2006

August 12, 2006
Second ROV Dive: First Use of PUP

AUV waiting for its next deployment.
The seas this morning were the calmest yet seen and the weather looked favorable, thus creating perfect ROV diving conditions. The AUV dive last night, however, did not go as well as planned. Due to a minor computer coding error, the AUV reversed the sign of its pitch in the water: when it was supposed to ascend, it descended and visa-versa. Fortunately, the craft was still able to keep its programmed course and return to the Flyer after seven hours. As this was the first time the AUV was launched from the Western Flyer, retrieving it back to the ship also proved to have its own difficultiesdue to launch/recovery crane head misalignments. All in all, the craft sustained no damage and will be ready to go, weather permitting.

Deploying Tiburon ROV with PUP attachment.

Today, the Brewer Lab Group’s main objective was to use PUP (Precision Underwater Positioner) to focus the standoff optic laser of DORISS on exposed methane hydrates along the ridge. This was not a particularly easy task, as yellow-tinged, bacteria-generated oils covered a large percentage of the hydrates, causing florescence and washing out the much weaker Raman signal. In addition, the highly variable topography of the canyon outcrops made finding stable positions for the ROV to land time-consuming and difficult.

The calm seas during the day provided perfect working weather for the ROV dives.

We did have considerable success today, however, as we were able to detect the hydrate gas (i.e. methane) signal with repeated exposures in quick succession. This marks the first time methane hydrates were chemically analyzed in situ in their natural formations on the sea floor.

The rest of the day was spent on multiple attempts with various techniques to obtain coring samples, including the use of heating probes and a serrated knife. While the coring tool was ultimately successful in removing the hydrate from the mound into the coring tube, extracting the sample from the coring tube itself proved incredibly difficult given the equipment setup at the time. Tomorrow’s experiment will use a hydraulic ram to push out the core, despite its inherent decreases in drilling efficiency.

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