If space explorers discover a biosphere supporting life on an off-Earth body, should they treat that life as possessing intrinsic value? This is an ethical quandary leading to a further question: how do we ground a universal moral norm to which the astroethicist can appeal? This article closely analyses various forms of responsibility ethics and finds them weak because they commit the naturalistic fallacy – that is, they ask nature to define the good. The good, however, is self-defining and not derivable from nature. Even so, a revised responsibility ethic could ground its universal norms on the fact that life and only life can experience and appreciate the good. Conclusion: living creatures possess intrinsic value both on Earth and elsewhere in the Universe.
