Will we ever colonize outer space？ 人类会把外太空变成殖民地吗？
“That depends on the definition of ‘colonize.’ If landing robots qualifies， then we’ve already done it. If it means sending microbes from Earth and having them persist and maybe grow， then， unfortunately， it’s not unlikely that we’ve done that as well—possibly on Mars with the Phoenix6） spacecraft and almost certainly inside the Curiosity rover7）.
If it means having humans live elsewhere for a longer period of time， but not reproduce， then that’s something that might happen within the next 50 years or so. But if the idea is to construct a self-sustaining environment where humans can persist indefinitely with only modest help from Earth， then I’d say this is very far in the future， if it’s possible at all. We currently have a very inadequate understanding of how to build closed ecosystems that are robust to perturbation by introduced organisms or nonbiological events （Biosphere 28）， for example）， and I suspect that the contained ecosystem problem will turn out to be much more challenging than the vast majority of space colonization advocates realize. There are a wide range of technical problems to solve， another being air handling. We haven’t bothered to colonize areas underwater on Earth yet. It’s far more challenging to colonize a place where there’s hardly any atmosphere at all.”
—Catharine A. Conley， NASA planetary protection officer
“这要看怎么界说‘殖民’了。假如机器人登陆算的话，那么咱们现已做到了。假如这意味着把地球上的微生物送上去，让其存活并成长，那么，很不幸，咱们很有或许也做到了——‘凤凰号’飞船登陆火星时或许就完成过，而在‘猎奇号’探测器内简直必定完成了。
假如树立殖民地指的是人类长时刻在外星寓居，但不繁殖子孙，那么大约在未来50年内就或许完成。但假如指的是制作一个自给自足的环境，让人类只需地球适度的支撑就能在其间无限存活下去，那么我以为就算或许，也是在非常悠远的未来。现在，咱们不知道怎么树立一个关闭的生态系统，使其能接受因为微生物引进或非生物要素（如生物圈2号）引发的细小改变。我以为其间的生态系统问题远远比绝大多数太空殖民倡导者所意识到的更具挑战性。有许多不同的技术问题要处理，另一个问题便是空气处理。咱们还未在地球的水下区域树立殖民地，而要在一个简直没有空气的当地树立殖民地，挑战性则更大。”
——美国国家航空航天局行星维护官员凯瑟琳·A·康利
