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Accueil > A propos du LPP > Communication > Actualités archivées > 2020 > Jupiter’s moon Europa : New evidence of watery plumes

Jupiter’s moon Europa : New evidence of watery plumes

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New simulations and 20-year-old data from NASA’s Galileo mission, indicate that Europa, Jupiter’s fourth largest moon, ejects water from its subsurface ocean into space.

Slightly smaller than Earth’s Moon, Jupiter’s moon Europa is one the smoothest objects in our Solar System (with no mountains or craters). Nevertheless its surface has a lot of texture, in the form of streaks and cracks engraved into a layer of water ice, which is thought to be about few tens of kilometers thick and floating on liquid water of 60 to 150 kilometers deep. This subsurface ocean, is thought to have twice as much water as Earth’s oceans, but its depth, composition and interactions with the deep interior and the icy crust remain unknown. This makes it one of the most tantalizing places in the solar system to look for life beyond Earth.
La lune glacée Europe, satellite de Jupiter vue par la sonde Galileo de la NASA

Many indirect evidence support the existence of a subsurface ocean on Europa already since the times of the Galileo mission. In addition to the mass of Europa and the way it interacts with Jupiter’s magnetic field, one of the big indicators is the presence of water being occasionally released from its icy surface into space, in cryovolcanic eruptions known as “plumes”.

In this new study of H. L. F. Huybrighs et al. GRL, 2020, and to which Lina Hadid has contributed, the authors find new evidences supporting the existence of the water plume at Europa. In this simulation- based study the authors investigated why fewer than expected fast-moving protons were measured in the vicinity of the moon during one of the flybys performed by the Galileo probe 20 years ago in the year 2000. While previously researchers had assumed that Europa itself to have obstructed the detector’s view, in this article the authors found that some of this proton depletion was actually due to a plume spouting water vapor out into space. As a consequence, disrupting Europa’s thin atmosphere, perturbing the magnetic fields in the region and so altering the behavior and prevalence of nearby energetic protons.

These water plumes, if they do indeed exist, may provide another way to sample the subsurface of Europa and this is only possible from direct measurements ! Fortunately the ESA upcoming Juice (Jupiter Icy moons Explorer) mission, planned for launch in 2022 to investigate Jupiter and its icy moons, will be able to confirm the presence of Europa’s ocean by directly sampling the particles within the moon’s water vapour plumes and also by detecting them remotely. LPP is highly involved in this mission by providing the Search Coils magnetometers, part of the Radio and Plasma Waves Investigation (RPWI, PI. J-E. Wahlund, IRF, Sweden).

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