It is Aurélien's turn to tell us his first dive with Nautile
When, from the deck, we watch the ocean swallow the yellow casing protecting the pilots and the scientist within, it is hard to imagine the atmosphere among the divers unleashing the Nautile from the Pourquoi Pas? On the morning of the departure, heads empty and the navigation chart in hand, we enter the titanium sphere and are lowered into the sea by an armada of experienced mariners, which in all takes less than 15 minutes.
Two geological features have enabled us to target zones of potential hydrothermal mount construction: volcanoes, showing thermal activity setting ocean currents in motion and faults, through which seawater penetrates to the earth's crust absorbing metals.
Recently established high resolution maps identify these structures and the aim of the dive was to find the inactive mounts in a context conjugating both features 4500 metres down.
Lying face down, nose against the porthole, we see the rare rays of sunshine slip away. Very quickly, artificial, cold night-time sets in, the sounder alone informs us that we are on the descent. After two hours, the Nautile's spotlights turn on to discover that we have changed worlds. Dunes of sediment sprawl before us, carved by faults, displaying volcanic rock outcrops.
The movement of the submersible is an extension of the extreme slowness of this mineral world. Time seems to expand but the clock remains consistent with the course of the sun : for 3 hours, we have been searching for the ancient hydrothermal mounts, without a trace. We decide to go to the foot of the volcano, the culmination of our dive.
On the way, we see shrimp, fish and holothurian before discovering what we have come to look for: a succession of hills spotted with oxides, a mark of passed hydrothermal activity, encircling the volcanic structure observed on the maps. When we arrive at the top of the volcano, we take a sample: the pilots, Franck and Olivier, conduct the operation with surgical talent. Fatigue starts to take hold after hours of concentration, unreality prevails and I start to nearly believe that our small yellow vessel is flying over another planet.
Before the ascent, and then by respecting decompression limits, we take seawater samples to be analysed by chemists on-board the ship. At 18h30, we reach the surface and are towed aboard. Only when we get to see the videos taken by the Nautile do I realize how extraordinary the experience was!