Fire on Earth . ... Credit Copyright: ( AFS , BLM ) Explanation: Sometimes, regions of planet Earth light up with fire. Since fire is the rapid acquisition of oxygen, and since oxygen is a key indicator of life, fire on any planet would be an indicator of life on that planet. ... Although causing many a tragedy, for many places on Earth fire is considered part of a natural ecosystem cycle . ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...