Which of the following is a biomarker that could be used from an observatory around a nearby star, with the right equipment, to identify the Earth as a planet with life:
A) the presence of a large moon around the Earth
B) free oxygen in the Earth's atmosphere
C) the abundance of micro-organisms in the deserts of the Earth
D) the fact that most of our atmosphere is made of nitrogen
E) ice in the Earth's polar caps
Section 30.4: The Search for Extraterrestrial Intelligence

Question

Quizplus · Accepted Answer

Free oxygen in the Earth's atmosphere is a strong indication of photosynthetic life, making it a biomarker that could be detected by observing the Earth from a distance with the right instruments. The other answer options are not necessarily indicative of life and would not be useful as biomarkers.

Which of the Following Is a Biomarker That Could Be