• The mission of NASA's Juno spacecraft has gone on longer than anticipated.
• Juno was supposed to orbit Jupiter 34 times. In orbit 47 right now.

The focus of NASA's expedition to Jupiter is now on Io, a sister moon that has provided a wealth of information about Ganymede and Europa. Io appeared to be a fiery scarlet moon in an infrared photograph taken by the space agency's Juno mission from 50,000 miles away (80,000 kilometres away).
The picture was taken on July 5 of last year and made public on Wednesday. As observed in its flaming areas, it has stunning outlines of lava flows and lakes.

But now, as part of its continuous study of the planet's inner moons, NASA's Juno mission is scheduled to take further photos from the Jovian moon Io on December 15. The solar-powered spacecraft has already completed close flybys of Europa and Ganymede, and it is currently in the second year of an extended mission.

Recent papers in the Geophysical Research Letters and Journal of Geophysical Research based on Ganymede's flyby on June 7 of last year have been released.

They include inferences made from information gathered on the moon's surface composition, ionosphere, interior, and interaction with Jupiter's magnetosphere during the flyby. The first 3D measurements of the ice shell are one of the early findings from Juno's flyby of Europa on September 9. During the flybys, the Microwave Radiometer (MWR) on board Juno provided a third dimension for the mission's study of the Jovian moons.

It allowed scientists to obtain information on the composition, temperature, and cleanliness of the water-ice crust as far as around 15 miles (24 kilometres) below the surface of Europa and Ganymede. According to visible-light imagery captured by the spacecraft's JunoCam and by earlier missions to Jupiter, the surface of Ganymede is made up of a variety of older dark terrain, fresher bright terrain, craters, as well as linear structures that may be connected to tectonic activity. 

When scientists combined the MWR data with the surface photographs, according to Juno's Principal Investigator Scott Bolton, they found that the differences between these various terrain types stretch beyond the surface level.

The city-sized impact crater Tros appears to be the coldest region, according to Bolton, who also notes that the young, brilliant landscape appears to be colder than dark terrain. According to the science team's early estimate, the conductive ice layer on Ganymede may be at least 30 miles thick on average, with the chance that it may be substantially thicker in some places.

During Juno's close approach to Ganymede in June 2021, the Magnetic Field (MAG) and Jovian Auroral Distributions Experiment (JADE) instruments collected data. It demonstrated evidence of the deterioration and restoration of the magnetic field connections between Jupiter and Ganymede. Similar occurrences with the moon's ultraviolet auroral emissions, which are organised into two ovals and surround Ganymede, have been observed by the ultraviolet spectrograph on Juno (UVS).

For the next 18 months, the Juno team will continue to concentrate on Jupiter's moon Io, which is home to the solar system's most active volcano.