The whole young earth creation argument is sticky because it is basically impossible to refute. If I told you the whole world was created 2 seconds ago, as is, how would you prove me wrong? So you just end up trying to point out the problems with every other proposed history of the universe - which is fine, it just ends up being a little unsatisfying.
By that standard, the argument for ANY age of the universe, young or old, is impossible to make.
Even though this article calls into question the overall age of Ganymede due to its magnetic field, there are other ways of measuring the age of planets, planetoids, and moons. The density of cratering on Ganymede points to a surface age of 3 to 3.5 billion years