Complex sentence: Murphy finds an ice core sample in the scientists' lab, and believes it to originate from a meteor crater; when ammonium hydroxide is detected in one of the corpses, Murphy theorizes that the core sample might be 250,000 years old.
Split into simpler sentences: Murphy finds an ice core sample in the scientists' lab, and believes it to originate from a meteor crater. When ammonium hydroxide is detected in one of the corpses, Murphy theorizes that the core sample might be 250,000 years old.