Infrared images from Juno provide the first glimpse of Ganymede’s icy north pole.
Editor’s note: Text in the first sentence regarding Ganymede’s size relative to Mercury has been corrected.
On its way
inbound for a Dec. 26, 2019, flyby of Jupiter, NASA’s Juno spacecraft flew in
the proximity of the north pole of the ninth-largest object in the solar
system, the moon Ganymede. The infrared imagery collected by the spacecraft’s Jovian Infrared Auroral Mapper (JIRAM) instrument
provides the first infrared mapping of the massive moon’s northern
Larger than the planet Mercury, Ganymede consists primarily
of water ice. Its composition contains fundamental clues for understanding the
evolution of the 79 Jovian moons from the time of their formation to today.
also the only moon in the solar system with its own magnetic field. On Earth,
the magnetic field provides a pathway for plasma (charged particles from the
Sun) to enter our atmosphere and create aurora. As Ganymede has no atmosphere
to impede their progress, the surface at its poles is constantly being
bombarded by plasma from Jupiter’s gigantic magnetosphere. The bombardment has
a dramatic effect on Ganymede’s ice.
data show the ice at and surrounding Ganymede’s north pole has been modified by
the precipitation of plasma,” said Alessandro
Mura, a Juno co-investigator at the National Institute for Astrophysics in
Rome. “It is a phenomenon that we have been able to learn about for the
first time with Juno because we are able to see the north pole in its
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.
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.
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
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.
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.
More information about
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Source: Jet Propulsion Laboratory