No matter which place space colonisation will target first – the Moon, Mars or a captive asteroid – there’s one, complex issue NASA and private contractors will have to tackle and solve first: gravity. Without a G-environment compatible with human physiology, no adventure into space is going to be of long duration.
By Stephen P. Bianchini|Serious Wonder
According to NASA, humans can withstand higher gravity than Earth, up to 4 g, while lower gravity is more problematic. Gravity itself is essential for human body – to keep muscles functioning, for example. They can vanish at a rate as high as 5% a week, as according to available data. If we look for habitats in the outer space near us, Venus is the only place with conditions close to Earth’s gravity (=0.9; too bad that the rest of the planet is so unwelcoming). Mars is the second best, with 0.38, and this is why actual planning for a Mars Colony is on the way. (The rest of the candidates are less interesting: Moon = 0.17, Titan = 0.14, Europa = 0.13, Ceres = 0.028.)
Brights - Die Natur des Zweifels 