Starbase One: The End of the World

Season 1, Episode 12. A huge comet is heading for Berengaria with the potential to cause total destruction. As the base crew prepare to destroy it, they discover a massive lifeform within, which causes a moral conundrum. Evacuation plans are carried out, putting further strain on Threv's family, while Grum butts heads with other Tellarites who show up to help.