This image of Ganymede was obtained by the JunoCam imager during Juno’s June 7, 2021, flyby of the icy moon.Credits: NASA/JPL-Caltech/SwRI/MSSS — This image of Ganymede was obtained by the JunoCam imager during Juno’s June 7, 2021, flyby of the icy moon.
***Credits: NASA/JPL-Caltech/SwRI/MSSS***

Space & Science News

The spacecraft flew closer to Jupiter’s largest moon than any other in more than two decades, offering dramatic glimpses of the icy orb.

The first two images from NASA Juno’s June 7, 2021, flyby of Jupiter’s giant moon Ganymede have been received on Earth. The photos – one from the Jupiter orbiter’s JunoCam imager and the other from its Stellar Reference Unit star camera – show the surface in remarkable detail, including craters, clearly distinct dark and bright terrain, and long structural features possibly linked to tectonic faults.

“This is the closest any spacecraft has come to this mammoth moon in a generation,” said Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio. “We are going to take our time before we draw any scientific conclusions, but until then we can simply marvel at this celestial wonder – the only moon in our solar system bigger than the planet Mercury.”

Using its green filter, the spacecraft’s JunoCam visible-light imager captured almost an entire side of the water-ice-encrusted moon. Later, when versions of the same image come down incorporating the camera’s red and blue filters, imaging experts will be able to provide a color portrait of Ganymede. Image resolution is about 0.6 miles (1 kilometer) per pixel.

In addition, Juno’s Stellar Reference Unit, a navigation camera that keeps the spacecraft on course, provided a black-and-white picture of Ganymede’s dark side (the side opposite the Sun) bathed in dim light scattered off Jupiter. Image resolution is between 0.37 to 0.56 miles (600 to 900 meters) per pixel.

“The conditions in which we collected the dark side image of Ganymede were ideal for a low-light camera like our Stellar Reference Unit,” said Heidi Becker, Juno’s radiation monitoring lead at JPL. “So this is a different part of the surface than seen by JunoCam in direct sunlight. It will be fun to see what the two teams can piece together.”

This image of the dark side of Ganymede was obtained by Juno’s Stellar Reference Unit navigation camera during its June 7, 2021, flyby of the moon.Credits: NASA/JPL-Caltech/SwRI — This image of the dark side of Ganymede was obtained by Juno’s Stellar Reference Unit navigation camera during its June 7, 2021, flyby of the moon.
***Credits: NASA/JPL-Caltech/SwRI***

The spacecraft will send more images from its Ganymede flyby in the coming days, with JunoCam’s raw images being made available here.

The solar-powered spacecraft’s encounter with the Jovian moon is expected to yield insights into its composition, ionosphere, magnetosphere, and ice shell while also providing measurements of the radiation environment that will benefit future missions to the Jovian system.