Actually the Lubavitcher Rebbe said that while there might be life on other planets there cannot be intelligent life there, because such people would need the Torah to tell them how to behave, and there can only be one matan torah in the universe.
I don’t understand this argument. Just as the Australian Aborigines and the inhabitants of sub-Saharan Africa and of the Americas had to wait thousands of years till the Torah could reach them, why could the same not be true for the inhabitants of Mars or Titan, or of some planet orbiting Tau Ceti? Until humans with the Torah contact them, Hashem may have left them to their own devices and judges them accordingly, just as He did with so many humans.