Jupiter has many moons, but Ganymede is one of the more special, according tomedia CNET. Ganymede is the largest moon in the solar system, larger than Both Mercury and Pluto, and has its own magnetosphere. It’s an unusual world, with an inner ocean, incredibly thin atmosphere and icy crusts. Since Galileo first discovered it in 1610, it has attracted the attention of astronomers.
Galileo’s discovery was immortal, but he did not have the tools to really examine the satellite. But 410 years later, NASA scientists did. On December 26, 2019, the Jovian Infrared Aurora Surveyor (JIRAM) on NASA’s Juno probe captured the first images of the Ganymede’s north pole, mapping the area for the first time.
These images show an unusual layer of ice in the North Pole that we won’t encounter on Earth because the magnetosphere filters particles from the sun — plasma — into its direction. If there is no decent atmosphere, it basically drops the plasma to the ice of Ganymede.
“JiRAM data show that the ice in and around the Arctic has been altered by plasma precipitation,” Alessandro Mura, a co-researcher on Juno from Italy’s National Institute of Astrophysics, said in a NASA news release. “This is the first time we’ve learned about it on juno because we can see the whole of the Arctic.”
Plasma prevents ice from appearing in structures that we usually see on Earth. When water freezes here, a crystalline structure is formed — layer after layer of water molecules form hexagonal rings. At the poles of Ganymede, ice takes on an amorphous form. Its molecular structure is disordered, with no lattices, no rings. Analyzing and understanding these structures will provide further clues into the formation of Jupiter’s moons and the forces in their evolution.
Juno should get some help over the next decade. The European Space Agency will seek to explore Ganymede when it launches the Jupiter Ice Moon Probe (JUICE) in 2022. It will reach Jupiter by 2029, and it should begin close-range scientific exploration of Ganymede around 2032. NASA will at the same time explore another interesting Jupiter moon, the Europa Clipper, an orbiting spacecraft that will study a satellite that could hold microbial life.