When things do not go as planned...
On August 9th 2007 the ROPOS ROV was deployed to recover Seismometer KESE in the Main Endeavour Vent Field. Upon reaching the bottom, KESE was quickly seen on the ROV video camera. A seismic sensor probe was pulled from a hole drilled in a Pillow lava formation using the ROV manipulator arm and secured on the ROV's equipment platform. To complete the retrieval of the KESE seismometer, the buoyant glass sphere (containing the electronic instrumentation and data logger) and attached anchor weight were to be picked up and also placed on the equipment platform.
When the manipulator arm contacted the buoyant glass sphere that is protected by a PVC "Hard Hat" shell, the wire rope connecting the float to the anchor weight suddenly let go of the anchor and the buoyant sphere ascended rapidly toward the surface. As we watched helplessly from the video monitors, the data cable connecting the seismic sensor probe to the buoyant instrument float quickly payed out and snatched the seismometer probe from the ROV platform. KESE, which began its journey at a depth of 2340 m, reached the surface in 40 minutes and was successfully retrieved with the valuable seismometer data intact.
The cause of the accidental release of the anchor was due to the use of two dissimilar metals to secure the cable to the anchor weight. After two years on the ocean bottom, the corrosion created by this electro-chemical imbalance had severely weakened a critical fastener thus resulting in the easy breakage and release of KESE. Unexpected problems and even simple oversights are a part of any scientific expedition. They challenge the scientific staff and ships crew to create innovative ways to solve these problems and achieve their scientific objective.