If Ganymede phases like Earth's moon then the earth would be a lot bigger. Ganymede is made of rock and ice so if it was Earth it would always be cold and icy. It stays on one side which means only one part of the sun gets hit by it. The pictures show a brief image of the Earth, sun, and moon. Earth would be a lot bigger and would always be cold if Ganymede phases like the moon then the earth would be a lot colder and icier. Some parts of the sun gets hit by it because it wouldn't be able to move
A host to feed off of, the right temperatures, basically the right living conditions for that type of bacteria. Most of the time it depends on the type of bacteria.
