On Monday (June 7), NASA's Juno probe zoomed within just 645 miles (1,038 kilometers) of Jupiter's enormous satellite Ganymede, which is bigger than the planet Mercury. It was the closest any probe had come to Ganymede since May 2000, when NASA's Galileo spacecraft got within about 620 miles (1,000 km) of the moon's icy surface.
It'll take some time to receive and process all the data from Monday's encounter, but we're already getting a taste: The first two photos from the flyby have come down to Earth, and NASA posted them online Tuesday (June 8).
One of the images, snapped by the JunoCam instrument, shows nearly an entire side of the crater-pocked Ganymede, which is thought to harbor a huge ocean of liquid water beneath its ice shell. (That ocean is likely sandwiched between two ice layers, however, so it's not as astrobiologically interesting as the subsurface seas of fellow Jupiter moon Europa and the Saturn satellite Enceladus. Those other buried oceans are in contact with their moons' rocky interiors, making a variety of complex chemical reactions possible, scientists say.)
The JunoCam photo, which has a resolution of about 0.6 miles (1 km) per pixel, was captured using the instrument's green filter. The image is black and white, but the mission team will be able to create a color portrait once the versions taken with JunoCam's red and blue filters come down, NASA officials said.