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The first spaceman to land on Earth may not be as friendly as ET。 In the latest bid to get us to cut greenhouse gases, scientists have decided that eco-conscious aliens disgusted by mankind's emissions could destroy our planet in disgust。 When observed from afar, the changes in Earth's atmosphere could label us as a civilization that has grown out of control。 Aliens reaching that conclusion may then launch a pre-emptive attack to protect this perceived threat to their own way of life。 电影《ET》剧照 But that is only one possibility. Scientists are also considering other unwelcome - and far-fetched - outcomes, such as aggressive extra-terrestrials who eat or enslave us, or perhaps they are industrial types who want to improve their own technological infrastructure and so pillage ours。 Lead researcher Shawn Domagal-Goldman and his team compiled a list of hypothetical situations to help us when we come into contact with other life forms。 Their suggestions include the issuing of warnings against broadcasts that might help aliens from learning about our biological make-up。 The first part of our contact, they add, should be limited to maths until we have a better idea of the type of ETI we are dealing with。 It would be particularly important for us to limit our emissions of greenhouse gases, since atmospheric composition can be observed from other planets。 | 
