Using data from the Jovian InfraRed Auroral Mapper (JIRAM) aboard NASA’s Juno spacecraft, planetary scientists have detected hydrated sodium chloride, ammonium chloride and sodium/ammonium carbonate, as well as organic compounds on the surface of Jupiter’s moon Ganymede.
The surface composition of icy satellites, beyond the ubiquitous presence of water ice, is an outstanding question with important implications.
The composition can provide clues to the origin and evolution of the body, and thus may set the stage for habitability.
Subsurface liquid water oceans, when present, may interact with the icy surfaces above, directly bearing on ocean habitability and detection of possible tracers of extraterrestrial life.
Ganymede, the biggest of Jupiter’s moons, has long been of great interest to planetary scientists due to the vast subsurface ocean.
Previous spectroscopic observations by NASA’s Galileo spacecraft and the NASA/ESA Hubble Space Telescope as well as ESO’s Very Large Telescope hinted at the presence of salts and organics, but the spatial resolution of those observations was too low to make a determination.
On June 7, 2021, Juno flew over Ganymede at a minimum altitude of 1,046 km (650 miles).
Shortly after the time of closest approach, the JIRAM instrument acquired infrared images and infrared spectra of the moon’s surface.
JIRAM was designed to capture the infrared light (invisible to the naked eye) that emerges from deep inside Jupiter, probing the weather layer down to 50 to 70 km (30-45 miles) below the gas giant’s cloud tops.
But the instrument has also been used to offer insights into the terrain of moons Io, Europa, Ganymede, and Callisto.
The JIRAM data of Ganymede obtained during the flyby achieved an unprecedented spatial resolution for infrared spectroscopy — better than 1 km (0.62 miles) per pixel.
With it, the Juno scientists were able to detect and analyze the unique spectral features of non-water-ice materials, including…
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