IN2P3/CNRS
In 1962, one of the world’s first underwater and human habitat research laboratories was established off the coast of Marseille, France, at a depth of 10 meters. Project Conshelf 1 consisted of a steel structure that accommodated two people for a week.
Now, more than 60 years later, another underwater laboratory is being set up not far from Marseille, this time to study the sea and sky. In contrast to Conshelf’s expertise, the Laboratorium Mediterania Souss-Marine Provence (LSPM) will not be inhabited by humans. Located 40 kilometers off the coast of Toulon at a depth of 2,450 meters, it is the first remotely operated underwater laboratory in Europe.
Underwater Physics
Today, three junction boxes capable of running multiple devices and fetching data is the essence of LSPM. The boxes, each measuring 6 meters long and 2 meters high, are connected to power systems on Earth via 42 kilometers of photovoltaic cables. The optical portion of this cable is used to collect data from the junction box.
Two of the junction boxes are assigned to the ORCA division of the Kilometer Cube Neutrino Telescope (KM3NeT). ORCA includes a three-dimensional array of 2,070 spheres, each containing 31 detectors called photo-multiplier tubes. The balls will be arranged in 115 lines anchored to the seabed and anchored by submerged buoys. Currently, 15 fonts have been installed.
The KM3NeT neutrino detector optical detection unit.
Patrick Dumas/CNRS
ORCA’s sister site, ARCA, is located off the coast of Sicily at a depth of 3,400 meters. Collectively, the ORCA and ARCA sites occupy more than 1 cubic kilometer of water.
“This giant detector array can detect neutrinos emitted from the skies of the Southern Hemisphere. [the neutrinos] They interact with water molecules, producing flashes of bluish light in the darkness of the ocean abyss,” said Paschal Coel, director of research at the Center de Physique des Particles de Marseille and director of LSPM for Ars Technica. “Detecting this light allows us to measure the direction and energy of the neutrinos.”
sound sensor
A third junction box is devoted to the study of marine science, including the so-called Albatross line, which consists of two one-kilometer long inductive cables that are attached to the ocean floor. This cable carries sensors to measure water temperature and ocean currents, as well as oxygen and pH levels.
That Laboratorium Geoazur, an institute of geosciences located near Cannes, has developed a wideband seismograph embedded in sediments on the ocean floor, enabling seismic data to be obtained in real time. Along with the seismograph, Geoazur researchers have transformed one of the optical fibers of a 42-kilometer photovoltaic cable into a giant array of Seismo-acoustic sensors.
View of the LSPM underwater platform, anchored at a depth of 2,450 meters.
Camille Combs, Overpoit Agency
This is not a traditional sensor but a flaw in the glass that appears during the manufacture of the optical fiber. This flaw is found in fiber optic networks. This is due to the heating and pulling process of the glass. As a result of this defect, part of the light is sent back to the transmitter,” said Anthony Sladen of the Geoazur Lab. He added that seismic or sound waves stretch or contract optical fibers, changing the path of light. inside it. “By measuring these changes, we can measure seismic and sound waves.”
Sladin and his team have turned the flaws in the glass lattice into 6,000 virtual sensors that can provide real-time data on earthquakes, underwater noise from ships and waves.
Another device consists of a group of hydrophones that can detect and record the sounds of whales and dolphins at different frequencies. The data will help scientists understand how frequently these cetaceans repeat locations, as well as their vocal behavior.
More to come
While the above-mentioned devices are in operation, another laboratory set already installed on the seabed is expected to be operational in the summer.
Most prominent among them is a robot called BathyBot, developed by the Mediterranean Institute of Oceanography, which can move on the ocean floor thanks to caterpillar tracks. BathyBot is equipped with sensors to measure temperature, oxygen and carbon dioxide concentrations, current speed and direction, as well as salinity and particle concentration.
BathyBot on BathyReef during tank testing.
Dorian Gilliman, Ohio Pythias State University
Controlled from shore and directed by a built-in camera, the robot will also be able to climb up to two meters of artificial reef and measure water properties of seafloor sediments.
Other instruments such as a gamma spectrometer to monitor radioactivity levels and a stereo single photon camera to measure the bioluminescence of deep-sea organisms are expected to start operating in the same timeframe.
According to Coyle, because the deep ocean is not well understood, facilities such as LSPM could advance our understanding of various phenomena.
“The main thing to learn is the long-term impact of global warming. LSPM observations have shown rising sea temperatures and lower oxygen levels even at this depth.
Dhananjay Khadilkar is a journalist based in Paris.
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