Old NASA Data Finally Explains Jupiter's Magnetic Moon Ganymede
As exciting as brand-new discoveries are, some of the most amazing finds are discovered when scientists look back on data (or artifacts) that never got the attention they deserved—like the data from the Kepler telescope that may still contain new exoplanets, or the creepy Shigir idol that was revealed to have a hidden animal face carved in it 100 years after it was discovered.
What makes Ganymede special is that it has its own magnetosphere, like Earth and Jupiter.
When it was discovered, this was a major find—no known moon in our solar system had a magnetic field like Ganymede, and no one expected them to.
Not only that— Ganymede had strangely bright auroras and a very strange, horn-shaped magnetosphere (as opposed to a more spherical one).
These discoveries were made by the Galileo satellite, which did a number of flybys on Jupiter and Ganymede, including one voyage that took it straight through a phenomenon called magnetic reconnection, caused by "the tangling and snapping of magnetic field lines."
While it was there, Galileo also saw huge strings of plasma (which is excited, electrically charged gas) passing between Ganymede and Jupiter.
These plasma flows are at the heart of the newly unearthed discoveries about Ganymede.
Looking at the Galileo info again, scientists were able to paint a new picture of Ganymede that involves plasma rain falling on the moon's icy poles and "an explosive magnetic event" happening between Jupiter and Ganymede's magnetospheres.
With this in mind, it looks like Ganymede is a much more dynamic, tumultuous place than we previously thought.
Considering it's got a thin atmosphere and a lot of magnetic...issues going on, Io is probably a better candidate for space colonization anyway.