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Researchers have spotted water vapor in Ganymede’s atmosphere

Researchers have spotted traces of water in the atmosphere of Ganymede, the largest terrestrial moon in Jupiter and the Solar System. One more reason to look forward to the JUICE mission, which will arrive there in 2032.

Thanks to the study of its magnetic field, we already knew that Ganymede, the largest of the moons of Jupiter and even of the solar system, harbors more water than all the Earth’s oceans combined. But according to the work of a team of astronomers, there could also be some in its atmosphere.

However, this is anything but obvious, because the gigantic aquatic stock of Ganymede is imprisoned under several tens of kilometers of ice. According to NASA, the water in the atmosphere could not therefore come from the evaporation of the reserves of the subsoil. To explain this discovery, the team led by Lorenz Roth of the KTH Royal Institute of Technology in Stockholm therefore looked at the other suspect: ice.

After multiple analyzes of the UV scans carried out by Hubble, they concluded that the water in the atmosphere was caused by the sublimation (passage from the solid state directly to the gaseous state) of this famous layer of ice. This phenomenon would take place at a precise moment of the rotation of the celestial body. Every day around noon (in Ganymedian time), the temperature rises significantly; near the equator, it would even be sufficient to tear water molecules from the frozen surface.

This observation certainly makes the European Space Agency even more impatient with its mission. JUICE, for Jupiter Icy Moons Explorer. This mission, whose probe was launched in 2022, will have the mission of exploring three of the four non-gas moons of the giant planet: Ganymede, of course, but also Europe and Callisto.

JUICE, a scientific suicide bomber in the lineage of Cassini

Its main goal will be to extract as much information as possible in the hopes of determining the habitability potential of these planets, as well as the likelihood of finding traces of life in them. It should arrive in the Jovian system in October 2029. A long series of complex maneuvers will then begin which will last nearly three years, in order to fly over the three moons mentioned above.

It will begin with a passage near Europe, before taking advantage of the rest of its trajectory to study Jupiter’s magnetosphere. Then, it will fly over Callisto, then pass again briefly over Europe. The last part of his journey will then come, with an insertion into Ganymede’s orbit scheduled for September 2032.

Once there, the probe will gradually lower its orbit to an altitude of 500 km; an ideal observation post to study the composition and the magnetic field of this frozen moon. She will stay there until her last breath; once it has almost run out of fuel, it will put on the brakes to dive directly towards Ganymede. On this occasion, the machine will probably reward us with some superb images; a bit like Cassini, the last cosmic suicide bomber to have sacrificed himself for science, author of a memorable last stand during his leap from the angel to the bowels of Saturn.

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