Ganymede: Ganymede is both the largest moon of Jupiter, our Solar System's planetary behemoth, as well as the largest moon in our entire Solar system. Observations of Ganymede by the HST in 2015 suggested the existence of a subsurface saline ocean. This is because patterns in auroral belts and rocking of the magnetic field hinted at the presence of an ocean. It is estimated to be approximately 100 kilometers deep with a surface situated below a crust of 150 kilometers.
The conspiracy that Fox missed (well, they do miss a lot) is called by its adherents "Alternative 3". Its promoters are shadowy individuals like Bill Cooper, a formal US Naval Briefing Team member with access to state secrets, who claims that an advanced American space presence is a reality. In Behold a Pale Horse, he reports that "A moon base, Luna, was photographed by the Lunar Orbiter and filmed by Apollo astronauts... I can say that 'Alternative 003' (a British TV documentary on this subject) is at least 70% true from my own knowledge and the knowledge of my sources."
The rifts themselves are buried far, far down, deep beneath dark volcanic plains on the near-side of our Moon and have been spotted only in the gravity data provided by GRAIL. The lava-flooded rift valleys are not like anything seen anywhere else on the lunar surface--but some planetary scientists think that they may have, at one time, long ago, resembled rift zones on our own planet, Venus, and Mars. The new findings are published in the October 1, 2014 issue of the journal Nature.