Re: The jury is out still,
It might be we need a world with gravity and not necessarily 9,81 m/s/s. Why not imagine exoskeletons for those who have been living too long on Mars and would like to visit their parents on Earth? Or a space station with wheels creating various acceleration fields so that those from Earth can visit those from Mars for a few weeks, only not on a planet but in a station? Earth and Venus have roughly the same gravity. Mercury and Mars have exactly the same gravity. The Moon, Ganymed, Europa, Titan, Triton have roughly the same gravity.