And so when it comes time when we find gases in exoplanet atmospheres that we won't know if they're being produced by intelligent aliens or by trees, or a swamp, or even just by simple, single-celled microbial life.
所以当我们在系外行星的大气中 找到了那些气体， 我们很难确定这些气体是怎么来的， 是由外星人制造的， 还是来自树木， 或者沼泽地， 或者仅仅是来源于简单的 单细胞生物。