Might not be a space station, could have been mined.
Precious metals? Or a moon converted into a space station, and mined to facilitate the manufacture of very large vessels for the exodus to earth or for exploration of the stars.
If we add the abundance of methane on Jupiter we could assume Jupiter as a refueling station for the long trip out of solar system.

Off topic
How does Jupiter's atmosphere contain so much methane?
The only way I have heard of to create methane is biological processes.
The conversion of methane to good usable hydrogen should be very easy using pyrolysis in a vacuum such as space.
Put a large amount of methane in a large vessel such as a hollowed out asteroid and put it close enough to the sun to raise the temperature to 1500 degrees Fahrenheit, the hydrogen bonds break and you have a container full of hydrogen and carbon no O2 so it doesn't burn.