I just had a thought, especially in view of more promise of human lunar and then Martian human surface exploration in the near future. We all know the advantage on Earth or geosynchronous orbit satellites. My thought and thread here for questions is what are members' thoughts about spot synchronous space stations or satellites above Mars, the Moon or perhaps other bodies such as Ceres or Venus or Jupiter's large Moons or Titan etc. Also what would be the altitudes required for such structures above their respective surfaces. Also what concrete plans are there so far for such facilities by NASA, ESA, China or others?