Large meteors kill people and make them unhappy. Meteor showers have no effect on the population.
Colonists_survived = Colonists * (Random(91)+10) / 100 Colonist_happiness_change = -(Random(31) + 50) Natives_survived = Natives * (Random(100)+1) / 100 Native_happiness_change = -(Random(31) + 50)
In simple words, up to 90% of the colonists and up to 99% of the natives die, and they lose 50 to 80 happiness points. The mineral amounts added to the planet's core (not surface!) are configurable (LargeMeteorOreRanges, MeteorShowerOreRanges).