The ice near both poles of the moon is amorphous. This is because charged particles follow the moon's magnetic field lines to the poles, where they impact, wreaking havoc on the ice there, preventing it from having an ordered (or crystalline) structure. In fact, frozen water molecules detected at both poles have no appreciable order to their arrangement, and the amorphous ice has a different infrared signature than the crystalline ice found at Ganymede's equator."These data are another example of the great science Juno is capable of when observing the moons of Jupiter," said Giuseppe Sindoni, program manager of the JIRAM instrument for the Italian Space Agency.JIRAM was designed to capture the infrared light emerging from deep inside Jupiter, probing the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter's cloud tops. But the instrument can also be used to study the moons Io, Europa, Ganymede, and Callisto (also known collectively as the Galilean moons for their discoverer, Galileo).Knowing the top of Ganymede would be within view of Juno on Dec. 26 flyby of Jupiter, the mission team programmed the spacecraft to turn so instruments like JIRAM could see Ganymede's surface. At the time surrounding its closest approach of Ganymede – at about 62,000 miles (100,000 kilometers) – JIRAM collected 300 infrared images of the surface, with a spatial resolution of 14 miles (23 kilometers) per pixel.The secrets of Jupiter's largest moon revealed by Juno and JIRAM will benefit the next mission to the icy world. The ESA (European Space Agency) JUpiter ICy moons Explorer mission is scheduled to begin a 3 1/2-year exploration of Jupiter's giant magnetosphere, turbulent atmosphere, and its icy moons Ganymede, Callisto, and Europa beginning in 2030. NASA is providing an Ultraviolet Spectrograph instrument, along with also subsystems and components for two additional instruments: the Particle Environment Package and the Radar for Icy Moon Exploration experiment.
NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for the agency's Science Mission Directorate in Washington. The Italian Space Agency (ASI) contributed the Jovian Infrared Auroral Mapper. Lockheed Martin Space in Denver built and operates the spacecraft.