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Data from the Cassini International Probe revealed complex organic molecules from Saturn's icy moon, Enceladus, reinforcing the idea that this oceanic world is home to conditions conducive to life.
We knew very little about Encelade before 2005 – the year Cassini flew for the first time. Since then, he has become a continuous source of surprises, with secrets still revealed even now, after the end of the mission.
During the spaceship's incredible career, scientists discovered that the Enceladus 500 km in diameter under a thick, icy crust, with powerful hydrothermal vents on the seabed that mix the materials of the porous core filled with moon water with ocean water.
They detected powerful geysers releasing a mixture of water vapor and ice from the oceans into space through cracks – nicknamed "tiger stripes" – in the icy shell of the moon, providing material for one of Saturn's rings
Now, a team led by Frank Postberg and Nozair Khawaja of the University of Heidelberg, Germany, has identified fragments of large organic molecules in these grains of ice ejected. The results are published today in Nature .
"It's the very first detection of complex organic matter coming from an alien aquatic world," Frank explains.
"We have found large molecular fragments that show typical structures for very complex organic molecules," adds Nozair. "These huge molecules contain a complex network often constructed from hundreds of carbon atoms, carbon atoms, etc." 39, hydrogen, oxygen and probable nitrogen that form substructures in the form of ring and chain. "
Fragments, up to 200 molecular weight units, researchers believe that before the collision, the grains contain the original molecules, even the largest, which could have molecular weights of thousands of atomic mass units.
Scientists calculate the mass molecular, or weight, as the sum of the weights of the individual atoms contained in the molecule Previously, Cassini had detected in Enceladus only light organic molecules, much smaller than the most recent fragments
Such molecules can only be created by complex chemical processes, including those related to life. Alternatively, they could come from the primordial material found in some meteorites or, more likely, be produced by hydrothermal activity.
"In my opinion the fragments we found are of hydrothermal origin, having been processed in the hydrothermally active core of Enceladus .: in the high pressures and high temperatures we expect, it It is possible that complex organic molecules may appear, "says Frank.
Recent simulations show that enough heat to fuel hydrothermal activity for tens of millions of years friction if the moon has a porous core with ocean water percolating through it.
In continuation of this scenario, organic matter is injected into the ocean by hydrothermal vents on the bottom of Enceladus' ocean – something that appears to be the sites hydrothermal found at the bottom of the oceans on Earth, which are one of the Earth's oceans, organic substances from deep water can accumulate effectively on the walls of ascending air bubbles, transporting them to the surface where they are scattered with spray. when the bubble bursts.
Scientists believe that a similar process could occur on Encelade. Gas bubbles, rising across dozens of kilometers of ocean, could bring organic matter from the depths where they form a thin film floating on the surface of the ocean under the shell of the ocean. ice cream
. organic materials, with a saltwater spray from the ocean. Tiny droplets of dispersed organic matter are covered with ice when the water vapor freezes on their surface and, with the frozen stream of salt water from the ocean, are ejected into the plumes and then detected by Cassini
. a long series of discoveries made by Cassini who painted Enceladus as a potentially habitable aquatic world.
However, with Cassini's data, it is not possible to confirm the exact origin of the newly found organic compounds from which the fragments observed. derive because the size of the fragments is at the maximum limit that could be detected by the instruments.
"If we could visit Enceladus again, we would take instruments capable of seeing whole molecules, not just those fragments, and would tell us exactly what they are and how they were created," Frank says.
"It seems that this mysterious moon will keep this secret for a while, but it is within the reach of a future mission to Enceladus to solve" Cassini's revelations will also have important implications for ESA Explorer's next explorations, Juice, which is expected to be launched in 2022, with an arrival at the Jupiter system in 2029. [19659005] Similar to Saturn, Jupiter has a complex system of natural satellites, with three of the largest – Europa, Ganymede and Callisto – thought to have an underground ocean
"Through the experience of Cassini, we will know what to look like Nicolas Altobelli, scientist of the project Cassini of the ESA and also responsible for the development of Jus's scientific operations at ESA. conditions where life could have emerged in our solar system. "
" Macromolecular Organic Compounds from the Depths of Enceladus "by F. Postberg et al, is published in Nature .
Learn more:
Scientists discover complex organic molecules of Enceladus
More information:
Frank Postberg et al. Macromolecular organic compounds from the depths of Enceladus, Nature (2018). DOI: 10.1038 / s41586-018-0246-4
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