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Nicolas Ligier (Open University) : «Ganymede and Europa: dolphin paradises ?»

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Lundi 19 Novembre 2018, 13:00 - 14:00
par Mickaël BONNIN

Icy bodies hold a privileged place in the Solar System as they can help to better understand the emergence of life on Earth due to their respective sub- glacial oceans. The three icy Galilean satellites, Europa, Ganymede and Callisto, are among the most exciting of them. Their diversity and their strong exobiological interest enticed NASA to conduct the ambitious Galileo mission in the late 90s. Significant science advances have been made thanks to this mission, but many question remain unanswered. Hence, ESA and NASA have decided that the Galilean moons, and especially the icy ones, will be visited once again during the next decade with two major dedicated space missions : Europa Clipper (NASA) and JUICE (ESA), with respectively Europa and Ganymede as main targets. Different instruments investigating the chemical and physical properties of the surface of these moons will be onboarded for the JUICE mission; one of them is MAJIS, an imaging spectrometer working in the visible and near-infrared wavelength range. In order to prepare the radiometric budget of this instrument and to bring added-values to Galileo/NIMS previous results about Europa’s and Ganymede’s surface properties, a ground-based observation campaign was led from October 2011 to March 2015 with the integral field spectrometer SINFONI, one of the instrument mounted on the VLT.
New results about the surface composition of Europa and Ganymede will be presented. Some spectra and large-scale composition maps will be shown and used to discuss the origin, endogenic or exogenic, of the chemical compounds existing on the surface of these two satellites. Extraterrestrial dolphins may not be far away any more...

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