NASA’s Juno collects key data on Jupiter’s moons

“The team is really excited to have Juno’s extended mission include the study of Jupiter’s moons. With each close flyby, we have been able to obtain a wealth of new information,” said Juno Principal Investigator Scott Bolton of the Southwest Research Institute in San Antonio. 

“Juno sensors are designed to study Jupiter, but we’ve been thrilled at how well they can perform double duty by observing Jupiter’s moons.”

Juno has already produced findings on the Ganymede’s interior, surface composition, and ionosphere, along with its interaction with Jupiter’s magnetosphere as well as the first 3D observations of Europa’s ice shell. These were all obtained during flybys of the moons.

Juno’s Microwave Radiometer (MWR) also provided a unique look beneath the water-ice crust of Ganymede and Europa to obtain data on its structure, purity, and temperature down to as deep as about 15 miles (24 kilometers) below the surface.

Exploring Ganymede's surface

Furthermore, visible-light imagery obtained by the spacecraft’s JunoCam was able to help the researchers understand Ganymede’s surface. It consists notably of a mixture of older dark terrain, younger bright terrain, and bright craters, as well as linear features that are potentially associated with tectonic activity.

“When we combined the MWR data with the surface images, we found the differences between these various terrain types are not just skin deep,” said Bolton. 

“Young, bright terrain appears colder than dark terrain, with the coldest region sampled being the city-sized impact crater Tros. Initial analysis by the science team suggests Ganymede’s conductive ice shell may have an average thickness of approximately 30 miles or more, with the possibility that the ice may be significantly thicker in certain regions.” 

But that’s not all. Juno’s close distance to the moons during the flyby saw it make use of its Magnetic Field (MAG) and Jovian Auroral Distributions Experiment (JADE) instruments to record data showing evidence of the breaking and reforming of magnetic field connections between Jupiter and Ganymede. 

“Nothing is easy – or small – when you have the biggest planet in the solar system as your neighbor,” said Thomas Greathouse, a Juno scientist from SwRI. 

 “This was the first measurement of this complicated interaction at Ganymede. This gives us a very early tantalizing taste of the information we expect to learn from the JUICE” – the ESA (European Space Agency) JUpiter ICy moons Explorer – “and NASA’s Europa Clipper missions.”