English: 20th July 2021

Juno’s Ganymede Close-up

This infrared view of Ganymede was obtained by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard NASA's Juno spacecraft during its July 20th, 2021, flyby. JIRAM "sees" in infrared light not visible to the human eye, providing information on Ganymede's icy shell and the composition of the ocean of liquid water beneath. It 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.

During the flyby, Juno came within 31,136 miles (50,109 kilometers) of the icy orb. Together with the previous observational geometries provided, this data gives the opportunity for JIRAM to see different regions for the first time, as well as to compare the diversity in composition between the low and high latitudes.

Because Ganymede has no atmosphere to impede the solar wind, or progress of charged particles from the Sun, 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: Ice is crystallized by heating at the equator and amorphized by particle radiation at the polar regions.