Why look so far. Recent evidence suggests Mars was, and possibly has been inhabited for over 100,000 years; very likely with our ancestors and of late with our best and brightest visiting regularly and instantaeously from nondescript office buildings in Langley...speaking of wormholes.
google "shadow space program" to discover how the highly classified but available technology to power travel there could either usher in a golden age or it's revelation utterly destroy the socio economic power structure here. With WW III seriously being bantered about as a way out of our financial hole; perhaps explains the wave of top clearance whistleblowers hoping for the former. The list includes top level NASA engineers, astronauts, analysts, consultants...NSA CIA
If true, Earth visitors report a breathable atmosphere, akin to geology of Arizona... a bit low on oxygen like higher elevations here, but adaptable.