These images the JIRAM instrument aboard NASA’s Juno spacecraft took on Dec. 26, 2019, provide the first infrared mapping of Ganymede’s northern frontier. Frozen water molecules detected at both poles have no appreciable order to their arrangement and a different infrared signature than ice at the equator.Credits: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM
The first-ever infrared images of Ganymede’s north pole, taken on December 26, 2019 with the JIRAM instrument aboard NASA’s Juno spacecraft, show that the gigantic moon’s polar ice lacks any crystalline structure like the water ice we’re familiar with typically does here on Earth. This is a result of constant bombardment by charged plasma in Jupiter’s powerful magnetosphere being funneled down onto Ganymede’s poles by the moon’s own internally-generated magnetic field, creating what’s known as amorphous ice.
Ganymede is the largest moon in the Solar System followed by Saturn’s Titan and then Earth’s Moon. It’s one of the four Galilean satellites easily visible from Earth in binoculars or small telescopes as small points of light arranged in a line next to Jupiter, along with Callisto, Io, and Europa.
Ganymede imaged by Voyager 2 on July 9, 1979 in visible-light wavelengths. Credit: NASA/JPL-Caltech. Color composite by Jason Major.
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