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Communication Dans Un Congrès Année : 2021

Science goals for future exploration of the habitability of the gaseous giant planets' satellites

Résumé

Large satellites of the gas giants Jupiter and Saturn, at orbits beyond the snow-line and the traditional "habitability zone", have been revealed as extremely astrobiologically interesting bodies presenting promising conditions for habitability and the development and/or maintenance of life. Jupiter's Europa and Ganymede show indications of harboring liquid water oceans under their icy crusts, which, in the case of Europa, may be in direct contact with a silicate mantle floor and kept warm through time by tidally generated heat. Around Saturn, Titan and Enceladus, were found by the Cassini-Huygens mission to possess active organic chemistries with seasonal variations, unique geological features and possibly internal liquid water oceans, among other. Thus, the icy satellites provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the Voyager and Galileo spacecraft revealed the potential of these satellites in this context. Their hydrospheres may be extremely thick (~600 km for Ganymede and Callisto for instance). The science goals for future exploration of the icy moons are broad and cover a large range of aspects from formation and evolution to habitability. In the case of Titan for example, the science objectives can be summarized as follows. - How do the satellites function as a system? How are the similarities and differences with Earth, and other solar system bodies, a result of the interplay of the geology, hydrology, meteorology, and aeronomy present in the systems? - What is the organic inventory available in the atmosphere and on the surface? How does this inventory differ from known abiotic organic material in meteorites and contribute to our understanding of the origin of life in the Solar System? What is the complexity of Titan's organic chemistry in the atmosphere, within its lakes, on its surface, and in its putative subsurface water ocean? - What is the exchange of energy and material between the Jupiter and Saturn magnetospheres, solar wind and their satellites? What is the source of geysers on Enceladus and Europa? Does complex chemistry occur in the geysers? These goals should be investigated in future missions exploring the icy moons around the giant planets. If the silicate mantles of Europa and Ganymede and the liquid sources of Titan and Enceladus are geologically active as on Earth, giving rise to the equivalent of hydrothermal systems, the simultaneous presence of water, geodynamic interactions, chemical energy sources and a diversity of key chemical elements may fulfill the basic conditions for habitability. In addition, Ganymede, the largest satellite in the Solar System presents unique features with its induced magnetic field, which can be connected to the presence of a liquid water undersurface ocean trapped between ice layers, as in the case of Europa, except that in the latter case the ocean is hypothesized to be in contact with the silicate core. Future exploration towards the Galilean satellites include missions such as ESA's JUpiter Icy moons Explorer (JUICE) (whose main target is Ganymede and will be launched in 2022 for arrival in the jovian system in 2030) and NASA's Europa Clipper mission. For a return to Titan, NASA has recently selected the Dragonfly mission and other concepts are being studied. Such endeavours will greatly enhance our understanding of the icy moons, their potential habitability and the formation of the Solar System in general
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Dates et versions

hal-03400072 , version 1 (24-10-2021)

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  • HAL Id : hal-03400072 , version 1

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Athena Coustenis. Science goals for future exploration of the habitability of the gaseous giant planets' satellites. 43rd COSPAR Scientific Assembly., Jan 2021, Sydney, Australia. ⟨hal-03400072⟩
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