Ganymede

1 Astronomers in two papers published Thursday in The Planetary Science Journal are the first to report that if you were to stand on the surface of Ganymede and Callisto, visible auroras would be dancing above.

2 Those moons are Callisto, Europa and Ganymede, the largest moon in the solar system.

3 Ganymede is one of three jovian moons that may hold hidden oceans, all potential habitats for life.

4 “Last year we flew by Ganymede,” says Scott Bolton, principal investigator of the Juno mission.

5 Juice — short for Jupiter Icy Moons Explorer — will spend three years buzzing Callisto, Europa and Ganymede.

6 Scientists have a new map -- the best created so far -- of the largest moon in our solar system, Ganymede, and it is both beautiful and revealing.

7 "So, Ganymede has had a tidal 'mid-life crisis', but its youngest 'crisis' remains enigmatic."

8 Europa’s icy shell is much thinner than Ganymede’s, perhaps just 15 kilometers thick, and its ocean may sometimes breach the surface—perhaps even sending plumes of water erupting into space.

9 In the time it takes Ganymede to orbit Jupiter, Europa orbits twice and Io orbits four times.

10 Mighty Jupiter turned up, with Io, Europa, Ganymede and Callisto, the four Galilean moons, in attendance.

11 Her adoption of a hoodie, a slouch and hip-hop slang makes for the most hilariously gender-confused Ganymede of recent memory: it's a joy witnessing her ridiculous attempts to be street in a forest.

12 Jericho Brown’s third poetry collection, “The Tradition,” opens with a poem called “Ganymede.”

13 Then in perhaps the most impressive feat of all, Juice will attempt to go into orbit around Ganymede: No spacecraft has ever orbited a moon other than our own.

14 There is no effective way for this heat, accumulated over billions of years, to reach the surface and be lost to space, and the radioactivity inside Ganymede and Callisto must therefore melt their icy interiors.

15 The spacecraft, the Jupiter Icy Moons Explorer or JUICE, will focus on studying several of the gas giant’s moons: oceanic Europa, massive Ganymede and quirky Callisto.

16 There’s also a triple resonance, 4:2:1, among Jupiter’s three moons: Ganymede, Europa and Io.

17 Orbital resonance, as seen with Jupiter’s moons, happens when planetary bodies’ orbits line up – for example, Io orbits Jupiter four times in the time it takes Europa to orbit twice and Ganymede to orbit once.

18 Even farther out, at Ganymede, Jupiter would have appeared scarcely brighter than today’s sun—a level of insolation with no significant impact on the moon’s ice.

19 The dominant atmospheric component of Callisto, Europa and Ganymede is molecular oxygen, which explains their newly discovered green and red auroral tints.

20 Astronomers had previously found clear signs of subsurface oceans on only two of Saturn’s moons—Enceladus and Titan—and on Jupiter’s moons Europa and Ganymede.

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