Day 4 - 24 well filed hours
3rd february 2022
Immersion of the Scientific Junction Box and the seismometer
Time has come for the first launching operation and it was a moment as important as delicate. After a short night, the mobilized teams were on deck at 4:00 am to send the SJB (from Ifremer) and the seismometer (from GeoAzur) to the bottom of the sea.
The SJB is an essential element : the devices at the bottom will be operationnal only thanks to it. Its role is to provide an electrical current and an Internet link to the devices located at 2400m: it's like an smart multi-socket. It is immersed with its 200 meters of cable that we see wound on the big coil. This cable will be necessary to establish a connection with the 'Node' of connection of the KM3NeT Neutrino Telescope (LSPM) already in place, relaying energy in the bottom coming from the earth.
The connection of the SJB cable to the 'Node' will be done later during the mission with the help of the Nautile submarine and its electronic arms. Tonight, the objective was to deposit the SJB on the bottom - one step at a time.
The seismometer was also deposited during this first descent. It is placed on the EMSO-WL site, at the same depth as the other devices, in order to monitor the gravity instability and understand the behavior of the sea floor. The EMSO-WL site is a multidisciplinary underwater observatory!
The SJB and the seismometer are well in place, at 3m from their target, at 2440m deep!
Crédit photo : Nicolas Fromont - @nicolasfromontphoto
Plankton sampling
Plankton is a group of animals and plants generally invisible to the naked eye, called respectively zooplankton and phytoplankton, and which moves with the currents. And this morning, it's some plankton sampling with the sunrise! Marthe is looking for bioluminescent micro-organisms.
The technical team on board deploys her plankton net. It's the simplest tool to collect small organisms. The water enters at the top of the cone and is filtered by guiding the particles to the bottom of the net called the collector.
Her net is immersed at a depth of 100m and brought up at a low speed (50cm/sec) to be as delicate as possible with the plankton.
Marthe will then identify the different groups of species in her collector. She will be particularly interested in those that emit light, and the bioluminescent organisms will be brought back to a MIO team for a more precise identification. This will help advance knowledge about bioluminescence in marine organisms!
Crédit photo : Nicolas Fromont - @nicolasfromontphoto
Looking for Marine Snow
In the lab, researchers are interested in a natural phenomenon with a rather poetic name: marine snow. This term is used to describe the organic debris formed in the upper layers of the water and which slowly drifts towards the sea floor. This debris is said to be organic because it's mainly composed of dead animals and plants (mostly plankton) and fecal matter. This decomposition phenomenon is comparable to the falling of leaves on the forest floor, except that it looks like a shower of flakes, hence the name "marine snow"!
It's a food source for many species, from the largest to the smallest. But it's also an important oceanic process in the carbon cycle:
At the surface, photosynthesis of phytoplankton (microalgae) generates carbon that is captured and continuously carried down by particles to the bottom. This is how the carbon is stored in the sediments of the ocean floor. Marine snow that sinks to a depth of more than one kilometer stores carbon in the deep ocean for more than 1000 years, which prevents the return of carbon to the atmosphere. We can therefore speak of carbon sequestration.
This rain of particles is slow: some flakes can fall for weeks before reaching their destination! The largest particles sink the fastest, and the smallest do not necessarily reach the bottom. The longer they fall, the more likely they are to be digested by an organism or colonized by bacteria... And that's what scientists on board are interested in! They are interested in the bacteria present in the marine snow.
Virginie Riou photography, CNRS - 2021.
The Marine Snow Catcher
To get marine snow without having to dive, you need to use a Marine Snow Catcher. It enables the sampling of marine snow particles with a minimum of trauma. It's a PVC structure in the shape of a bottle with a 100L volume, only it has two openings: one at the top and one at the bottom.
The operation is simple: it's immersed in an open position at the desired depth (Marc and Chloe sent it to 100m) and then, once filled, it is closed on command from the deck. The Marine Snow Catcher captures the desired water column and brings it up smoothly. After recovery, the device remains upright on the deck for 2 hours to allow the marine snow particles to sink to the bottom. This is the decanting phase. Then, with great care, the first 95 liters that do not contain particles of interest must be evacuated through a tap. The lower part of the water bottle contains the remaining 5 liters of water and the marine snow. This is the recovered part for the laboratory!
On the picture, Najib and Marc are recovering the Marine Snow Catcher from the crane to let it settle.
Crédit Photo : Nicolas Fromont - @nicolasfromontphoto
Breaking news for radiometry !
This is the second instrument launch of the day! The CPPM radiometer left to join the underwater observatory this morning and it's the first radiometer sent to this depth in the Mediterranean sea!
But what exactly is a radiometer? It's a tool that allows the measurement of radioactivity. It's important to know that radioactivity is an omnipresent natural phenomenon. It's due to atoms that are looking for stability: when atoms have a surplus of energy, they disintegrate by ejecting part of their neutrons and protons to find a more stable form. All this generates radiation and it's called radioactivity.
(Radioactivity can also be artificial, as it is in nuclear power plants)
This radiometer has been designed on a tripod to be stable, and its radioactivity detector is oriented downwards to protect itself from falling particles. If it's covered, it will not be able to make any measurements! The long tube above the detector is the probe : it recovers and processes the information perceived by the detector. And higher up is the electronic container of the radiometer. The whole is protected by a cover : the disc at the top of the infrastructure. The radiometer is part of the devices connected to the Scientific Junction Box.
Thanks to this radiometer, the CPPM researchers will be able to follow the measurements of radioactivity in the depths - a radioactivity that is still unknown!
Crédit photo : Nicolas Fromont - @nicolasfromontphoto
BathyBot's launch
It's BathyBot's turn to join the EMSO-WL site at 2500m deep! This robot was designed by Christian Tamburini and Severine Martini, and its technical aspect was carefully developed by Carl Gojak and his team (INSU, MIO, OSU - CNRS).
BathyBot is a benthic robot, in other words it's a robot that is intended to travel on the seabed. Its mission is to study the bioluminescence and this in a rather new way thanks to a hypersensitive camera. BathyBot is equipped with cameras and sensors that will allow to observe the biodiversity and to study the flow of particles. Researchers hope to understand the biogeochemical dynamics of the deep environment (biogeochemistry is about the transformation of organic matter, and major elements such as carbon, under the effect of biological, geological and chemical processes: Bio-Geo-Chemistry).
BathyBot is put in the water in its BathyDock, a rallying point, on which one clearly distinguishes two coiled cables, a red and a blue one. To function, the BathyDock will be connected on the Scientific Junction Box (the smart multi-socket of the bottom) thanks to the red cable. The blue cable will serve as a leash for BathyBot: he will be able to circulate around the BathyDock while being attached to its structure - while receiving electricity and internet for image transmission. The orange rectangles are floats allowing the cable to float. They are ingeniously designed because they allow the leash to form a floating arc when deployed, which prevents BathyBot from getting tangled!
The submarine the Nautile will soon leave for the bottom of the site to verify that BathyBot has arrived!
Crédit Photo : Nicolas Fromont - @nicolasfromontphoto