Juno probe to fly over Jupiter’s largest satellite

This Monday, June 7, 2021, at 7:35 p.m., the Juno probe will perform a low-level flight over the Ganymede satellite, just 1,038 km from its surface. A first since the Galileo spacecraft (Nasa) in 2000. Juno thus confirms his good health (read the monthly Sciences et Avenir n ° 892 p.40-43) and offers a unique point of view on the largest satellite in the entire Solar System (with 5,262 km in diameter it exceeds the planet Mercury), and one of the most fascinating …

Clean ice and dirty ice

About three hours before the overflight, the probe will aim its instruments on Ganymede in order to study the icy surface of the satellite, in particular its temperature and its composition.“The ice crust has light areas and dark areas, which suggests that some are pure ice, and others are dust-soiled ice., explains on the NASA site Scott Bolton, the head of the mission. Thanks to Juno’s radiometer, we will have the first study on the composition and structure of ice as a function of depth. This will lead us to a better understanding of how this crust forms, and keeps reforming. ” An in-depth analysis all the more interesting as the overflights by Galileo revealed that under this crust hides an ocean of salt water …

A meeting at 68,000 km / h

The probe will also study the Ganymede magnetosphere, a kind of bubble made up of electrically charged particles, generated by the star’s magnetic field. Ganymede is indeed the only satellite in the Solar System to have a magnetic field. As for the photo sequence, it will last about 25 minutes, when the probe will shave Ganymede at more than 68,000 km / h! According to the engineers of the mission, this will leave just enough time to take about 5 shots… Juno will thus prepare the ground for the European Juice mission, which is due to take off in 2022. Scheduled to arrive in the vicinity of Jupiter in 2030, it will be in operation. orbit around Ganymede in 2032, becoming the first probe to orbit a moon in the Solar System.

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