This week in 1610, Galileo Galilei discovered #Jupiter's four largest moons. Our @JUICEmission will study three of them! Read more about these icy worlds:
🌕 Ganymede ➡️ https://t.co/pkoOUSeJ46
🌗 Europa ➡️ https://t.co/HI2fj90mAf
🌑 Callisto ➡️ https://t.co/aete14gUPa#OTD pic.twitter.com/vSs4Tv0BB1

— ESA Science (@esascience) January 13, 2018