Ar? w? ?l?n?? M?ght E?rth be th? ??l? ?x???t??n t? ?n ?th?rw??? d??d un?v?r??? W? shouldn't b?. Th? ?ngr?d??nt? f?r life is everywhere - l?f? ?h?uld b? ??mm?n. But then, where is ?v?r??n?? Ar? hum?n? f?rm?d ?ut of ?xtr?t?rr??tr??l?, d? ?l??n? r??ll? ?x??t, wh?t ?nflu?n?? d? they h?v? on our w?rld? Th?? b??k ?x?l??n? th? ?????bl? ?n?w?r? t? th??? questions. B? th? t?m? ??u f?n??h r??d?ng, ??u w?ll h?v? a f?rm gr??? ?f th? r?l?v?nt science, ?n?ugh t? f?rm ?n ???n??n on wh??h ?n?w?r ?? ?r?b?bl? right.