[alexander_busek]

Ceres could be a future source of water if we ever need it for space travel or colonizing.

Looks like old Isaac Asimov was, sadly, wrong on both counts:

https://en.wikipedia.org/wiki/The_Martian_Way

1) The rings of Saturn do not have mountain-size constituents, and

2) There would be no reason to go that far anyway, as the Main Asteroid Belt is much closer.

(In fact, could it be that Phobos or Deimos themselves have a high water content?)

Regards,

[Moonman62]

(In fact, could it be that Phobos or Deimos themselves have a high water content?)

...

If they do have anything we need they are in a good location, since the gravity and atmosphere of Mars can be used for braking the speed of a spacecraft.