Mabel's recovery from the ocean floor off Antarctica.
[Update 2007-02-20: The recovery attempt was not successful, reports Polarstern. Mabel will stay on the ocean floor for another year.]
The joint German-Italian project "Mabel" (Multidisciplinary Antarctic BEntic Laboratory) is the first scientific project to be conducted during the current Antarctic Polarstern Expedition ANT-XXIII/9. Mabel is a deep-sea observatory; during a joint German-Italian project a year ago it was taken to a depth of more than 1,800 meters underwater and then released.
During the past year, a variety of measuring instruments have collected, processed, and stored the data. The on-board instruments include a seismograph, a CTD (Conductivity, Temperature, Density) measurement device, a transmissometer, current and speed recorders, Ph and redox potential recorders and a water sampler.
The job of the Mabel crew during the expedition is to recover the observatory from the ocean floor. They do this with the help of a second piece of equipment called Modus (Mobile docker for Underwater Sciences). Modus is reminiscent of a large funnel-shaped diving bell, which has a "Mabel connector" or docking pin located in the middle.
The position of Mabel on the ocean floor is located via GPS, and then the team lets Modus slowly down into the ocean, connected by a long steel rope. Large reflectors, 4 cameras, sonar and automated drivers make work with the Modus possible. Power connections, controller, and video signals are all contained within a fiber-optic cable that is contained within the steel rope.

Modus is prepared for ther recovery operation.
Modus is positioned on top of Mabel, and the docking pins are oriented in the correct position and connected. As soon as this is complete, Mabel can slowly be brought to the surface. This must be done carefully, and at the surface special care must be taken, as Mabel is still connected to the steel cable and there is a danger that wind or waves might push Mabel into the side of the Polarstern.

The advantage of such an observatory located on the ocean floor is that it is able to collect many different types of scientific data over a long time period in any location. This greatly expands the traditional possibilities of data collection using ships or stations. Mabel is an advanced example of the possibilities for further use of deep sea observatories in polar regions. The use of such technology could build an extensive deep sea network, in which more such observatories could work together and simultaneously record scientific data in different locations.

An earlier German Italian joint project was "Orion" (Ocean Research by Integrated Observatory Networks), which successfully collected data from a depth of 3,320 meters over 14 months in the Mediterranean during 2003-2005.
Technical Data from Mabel:
- Length: 3.00 meters
- Width : 3.00 meters
- Height : 2970 including the docking pin
- Weight: 1050 kg in air, 750 kg in water
- Cable weight: 2350 kg/m, 1700 kg/m in water
- Deepest diving depth: up to 6000 meters deep
Scientific Instruments
- Wideband Seismometer: collection of earth movements
- CTD: Light conditions, temperature, and density to measure the salt concentration
- Transmissometer: measurement of water clarity, floating water particles
- Current and speed measurements: collecting information on amount and direction
- pH and Redox potential mearuring instruments: for basic parameters ofwater analysis
- Water sampler: taking samples every 8 days to obtain a yearly profile
Text & photos: Michael Trapp, Alfred Wegener Institute
Submitted February 9, 2007