Learn about extraterrestrial life in the Arctic. No, this is not a synopsis of the new version of the movie. Thing. These are particularly complex missions to a hydrothermal vent located in the Arctic north of Greenland, under five meters of ice and at a depth of four kilometers.
In 2001, exploration work was carried out in the Gakkel ridge between Greenland and western Russia. A ridge is a contact line between two tectonic plates that are moving away from each other. Surprise: we caught the hallmark of hydrothermal vents – these are areas of the seafloor where underground magma comes into contact with seawater. Chris German, a geophysicist at the Woods Hole Ocean Institution (WHOI) in Massachusetts. “Normally, magma is no longer hot when it comes into contact with seawater.”
M. German had not finished being amazed. In Nature Connections, In late October, he describes how the Aurora hydrothermal vent in northern Greenland’s Gakkel Range was covered in 10 to 100 times more minerals than expected. “Hydrothermal vents in the Slow Ridges were thought to last only a few centuries. But the Aurora has been around for several thousand years, even 10,000 years. This means that it produced many minerals, such as copper, found on the seabed around Aurora. Therefore, underwater mine projects are more promising than we think. »
Another expedition to Aurora in the summer of 2021 by the Norwegian company REV Ocean further demonstrated the exceptional nature of this Arctic hydrothermal vent. “We have discovered a snail species that has only been observed in Antarctica,” explains biologist Eva Ramirez-Llodra from REV Ocean. “We wonder how they found it in the antipodes of the Earth. Further south, there are also species of animals and algae that exist in hydrothermal vents in the Atlantic and Pacific oceans. Because Aurora is isolated by numerous undersea mountain ranges, it is unclear how these species got there. REV Ocean was founded by a fishing magnate from Norway.
Hydrothermal springs ab
The first underwater hydrothermal vents were discovered in 1977 near the Galapagos. Unlike photosynthesis, which converts sunlight into energy, the life-sustaining chemosynthesis that takes place near these hydrothermal vents gets its energy from chemicals escaping from them, including sulfur. Hydrothermal vents owe their heat and special chemical composition to magma released from tectonic plate junctions. In the magazine in 2019 Nature Ecology and Evolution, researchers from University College London have shown that life on Earth could have emerged from the depths in these hydrothermal vents and then adapted to photosynthesis at the surface. Aurora is the only arctic hydrothermal vent. The previous northernmost hydrothermal vent was Loki Castle, discovered in 2008 in the far north Atlantic between Greenland and Norway.
Europa and Enceladus
The European moons of Jupiter and Saturn’s Enceladus are covered by an ice layer several tens of kilometers thick, and oceans 40-50 kilometers deep below it can support life based on chemosynthesis. “Studying the aurora allows us to understand what life would be like on Europa or Enceladus,” says Alman. Photosynthesis is not possible here. »
Since the Europa Clipper missions (planned for Europa in 2024) and the Enceladus Orbiter and Lander (proposed to Enceladus last spring by the American Academy of Sciences) will not be able to penetrate this ice sheet, it will be necessary to detect its existence. other than extraterrestrial life. “Gases cannot pass through the ice, but the ice itself moves and migrates to the surface,” she explains.I Ramirez-Llodra. In addition, there are ice jets on the surface of Europa and Enceladus originating from ice fractures. That’s why NASA is so interested in discovering evidence of chemosynthesis in ice. »
Ice pack sliding
In 2014, the first pictures of “Aurora” were hardly taken. “We searched and searched the hydrothermal vent throughout the month-long campaign,” says Alman. But since we only had 20 minutes to explore one area at a time, we couldn’t find it. On the last dive we finally found it and managed to capture less than a minute of footage. The problem with studying the aurora is that the scientific vessel cannot move through the air, as it does when exploring at great depths in open water. “Using motors to break ice is very intensive, we run the risk of breaking the power cable of the underwater robot,” says Mr German. In open water, the engines can be used gently to maintain position. But to investigate the Aurora, the ship shuts down its engines and slides along the ice. A second WHOI expedition was needed in 2019 to measure the aurora.
A semi-autonomous robot
The first two explorations of the Aurora hole in 2014 and 2019 used an autonomous stationary robot that was simply towed by a science vessel. Last summer, the REV Ocean expedition used a motorized robot named Aurora, which extended its observation time over the hydrothermal vent to 40 minutes.
The WHOI cruise planned for next summer will take a big step forward with the Nereid UI robot, equipped not only with autonomous movement, but also with batteries that give it about ten hours of autonomy. “So the only connection needed with the ship is the robotic arm and the communication cable to manipulate the sampling equipment,” explains Michael Jakuba, an engineer at the World Health Organization who developed Nereid.
“Since it is a lighter cable, we can reach 20 km. This will allow Nerei to stay over the Aurora for two to three hours. If necessary, the Nereid can even cut the communication cable and return to the ship on its own. Mr. Jakuba believes that Nereid UI technology could progress to tens of kilometers of communication cable, which could allow us to break through the ice sheets of Europa or Enceladus and directly study their oceans.
five meters of ice
In this part of the Arctic, the thickness of the ice does not change much with the seasons, because the arctic gyre causes the pack ice to accumulate there. The thickness of the ice is always at least one meter and can reach five meters. “We had to take a detour to reach our target in 2019 because the ice in a straight line was too thick for the accompanying Norwegian icebreaker,” says Alman.
20 years of discoveries
2000 : Probe Galileo Detects magnetic signals from the salty ocean in Europa.
2005 : Probe cassini It reveals jets of ice that indicate the presence of an ocean on Enceladus.
2013 : Hubble He sees similar ice jets over Europa.
2017 : cassini Discovers evidence of chemosynthesis on Enceladus.
Source: Woods Hole Ocean Institute (WHOI)
- Water temperature near hydrothermal vents
SOURCE: National Oceanic and Atmospheric Administration (NOAA)
- 100 meters
- Width of Aurora Hydrothermal vent
SOURCE: Woods Hole Ocean Institute (WHOI)