NASA has released the first images of the North Pole of Jupiter’s largest moon, Ganymede, taken by its Juno deep space probe. This infrared image taken on December 26, 2019 shows a glassy ice in the polar region of Jupiter’s infrared aurora surveyor (JIRAM) from the spacecraft.
As far as satellites are concerned, Ganymede is an “alien” in many ways. As one of the four largest Galileo moons in Jupiter’s 79 moons, Ganymede is the largest in the solar system. In fact, it is the ninth largest object in the solar system, even larger than Mercury.
Ganymede is also the only moon with its own magnetosphere, which may have been caused by the influence of Jupiter’s tides on the interior of Ganymede. According to NASA, the magnetosphere acts like the Earth’s magnetic field, with magnetic lines coming from the sun’s channels of charged particles or plasma, creating the famous aurora seen in polar regions. However, since Ganymede has no atmosphere, these particles can bombard much of the ice that makes up the surface of a giant satellite.
The Juno’s JIRAM instrument now has some understanding of the effects of these particles on ice. JIRAM is designed to capture infrared light from a depth of 30 to 45 miles (50 to 70 kilometers) from Jupiter’s interior. However, NASA said the instrument could also be used to examine Galileo’s satellites, Io, Europa and Callisto.
In this case, jiRAM was able to collect 300 infrared images of the surface, with a spatial resolution of 14 miles (23 kilometers) per pixel, as the Juno flew over the North Pole at a distance of 62,000 miles (100,000 kilometers). This allowed the instrument to detect a peculiar feature on polar ice that is not visible at the equator.
Juno discovered that the ice at the Ganymede’s north pole was bombarded with solar particles, turning it into so-called amorphous ice. In other words, it is not a solid, but a cold liquid. All suitable solids have crystal structures, with atoms arranged in an orderly manner. Ordinary ice has a crystalline structure, but NASA says particle bombardment spelt makes ice in the Ganymede region amorphous. This is because solar particles prevent the crystallization of ice molecules by constantly destroying the structure of the ice.
“JiRAM data show that the Ganymede and the surrounding ice have been altered by plasma precipitation,” Alessandro Mura, a co-researcher at Juno at 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.”