From the Galileo mission over 20 years ago. The data comes from the first flyby of the moon. I worked with a group that would collect all sorts of data and it went to two places, one into a US federal aide report to get money to collect more data to put into the next years federal aide report (and so on) and the other place was a file cabinet. The data amounted to nothing at all. Now not ALL of the people wasted the data but some did. Terrible. So when I see data that gets multiple looks it makes me smile. Thankfully ESA and NASA are both taking fresh looks at old data.
And this is new Ganymede data so it is REALLY fun.
NASA: Far across the solar system, from where Earth appears merely as a pale blue dot, NASA’s Galileo spacecraft spent eight years orbiting Jupiter. During that time, the hearty spacecraft — slightly larger than a full-grown giraffe — sent back spates of discoveries on the gas giant’s moons, including the observation of a magnetic environment around Ganymede that was distinct from Jupiter’s own magnetic field. The mission ended in 2003, but newly resurrected data from Galileo’s first flyby of Ganymede is yielding new insights about the moon’s environment — which is unlike any other in the solar system.
“We are now coming back over 20 years later to take a new look at some of the data that was never published and finish the story,” said Glyn Collinson, lead author of a recent paper about Ganymede’s magnetosphere at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We found there’s a whole piece no one knew about.”
The new results showed a stormy scene: particles blasted off the moon’s icy surface as a result of incoming plasma rain, and strong flows of plasma pushed between Jupiter and Ganymede due to an explosive magnetic event occurring between the two bodies’ magnetic environments. Scientists think these observations could be key to unlocking the secrets of the moon, such as why Ganymede’s auroras are so bright.
In 1996, shortly after arriving at Jupiter, Galileo made a surprising discovery: Ganymede had its own magnetic field. While most planets in our solar system, including Earth, have magnetic environments — known as magnetospheres — no one expected a moon to have one.