Exoethics adrift off Kepler-442

Face an impossible ethical dilemma in this Star Trek inspired scenario as you encounter an apparently intelligent swarm of alien nanites that has nonetheless slain all four of your crewmates. Are you morally forbidden or required to exterminate the nanite swarm, bearing in mind they might represent an entire civilization's worth of culture and life experiences despite the obvious existential threat they present? Can you establish contact and broker peaceful coexistence—at least until the Terran Stellar Guard can rescue you from your derelict research vessel?