See the first images NASA’s Juno captured as it sailed by Jupiter’s giant moon, Ganymede

NASA’s Juno spacecraft did a flyby of Jupiter’s giant moon Ganymede on June 7. It was the closest any spacecraft has flown to Jupiter’s largest moon in more than two decades. NASA has published the first two images from the flyby.

One photo was captured by the craft’s JunoCam imager. The other shot was captured by Juno’s Stellar Reference Unit star camera. Both images show Ganymede’s surface in spectacular detail, revealing craters, distinctly dark and bright terrain, and long structural features that NASA states may be linked to tectonic faults on the moon.

‘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.’

Of the JunoCam image, NASA writes, ‘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.’

‘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

At the time of Juno’s approach, the spacecraft was within 1,038km (645mi) of Ganymede’s surface. Juno is a spin-stabilized aircraft with a rotation rate of 2 rpm, and JunoCam has a fixed field of view. NASA writes, ‘To obtain Ganymede images as Juno rotated, the camera acquired a strip at a time as the target passed through the field of view. These image strips were captured separately through the red, green and blue filters. To generate the final image product, the strips must be stitched together and colors aligned.’

The required navigation and other ancillary information provided by precision observation geometry are not yet available, so the image above is a preliminary product. We’re looking forward to sharing the final color image with you as soon as it’s available.

The Stellar Reference Unit, which is a navigation camera that keeps Juno on its course, provided a black and white image of Ganymede’s dark side, which like with our moon, is the side opposite the Sun. The dark side is lit dimly by reflected light from Jupiter’s surface. The image resolution of the Stellar Reference Unit’s camera is between 600 to 900 meters (0.37 to 0.56mi) per pixel.

‘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

Juno’s recent close encounter with the Jovian moon, Ganymede, is expected to shed insight into the moon’s composition, ionosphere, magnetosphere and ice shell. Juno is also meant to provide measurements of the radiation environment, which will hopefully benefit future missions to Jupiter.

‘ 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.’

Juno will be sending additional images from its Ganymede flyby soon, which will be visible here. To learn more about the Juno mission, visit NASA’s dedicated website.