Spectral Fingerprints of Earth-like Exoplanets

In a famous paper, Sagan analyzed a spectrum of the Earth taken by the Galileo probe, searching for signatures of life. They concluded that the large amount of O2 and the simultaneous presence of CH4 traces are suggestive of biology. In this talk we discuss the biomarkers at different wavelengths and focus on what makes a habitable planet, using Earth as our example. We discuss surface, clouds and biosignature evolution over geological time. We look at biomarkers on planets around different stars, and set the measurements in context with physical characteristics of a planet. The search for signs of life implies that we need to gather as much information as possible in order to understand how the observed atmosphere works physically and chemically. How do we find them? How do we pick our targets? We live in an exciting time when comparative planetology is a reality, and the spectroscopic detection of life's signatures on worlds orbiting other stars maybe achievable within a generation.