Scientists have recorded an increase in the delta to the 18th power cap o ratio in foraminifera shells deposited shortly after the Chicxulub asteroid impact. This means there was more “heavy oxygen” in the foraminifera shells after the impact. What does this tell you about the climate conditions immediately following the asteroid impact?

Foraminifera build shells from oxygen in seawater. In colder water, their shells tend to contain a higher proportion of heavy oxygen-18, raising the δ¹⁸O ratio. So the increased ratio indicates that conditions became colder immediately after the impact; the correct choice is “It got colder.”

AI-written and checked against the verified answer.