Discussion Questions: Detecting Life on Other Planets

Explain the evidence that scientists use to infer the presence of carbon dioxide, water, methane, or ozone in the atmosphere of another planet.
Why do scientists examine absorption spectra to try to identify extraterrestrial life? What assumption are they making when they use this technique?
What is meant by a "golden fingerprint"? Why is there a different fingerprint for different times in Earth's history?
Is it possible that life forms can be found on planets with very different atmospheric compositions than that of Earth? Explain.