AbstractsAstronomy & Space Science

The search for a second genesis of life outside Earth is now well and truly underway with the first rocky exoplanets detected in the central star’s liquid water habitable zone. Recent results based on population studies show that small planets are abound in our galaxy. With the next generation of space- and ground-based telescopes on the horizon, it is critical to determine the best candidate exoplanets to follow up on for potential habitability and life. This PhD thesis shows how colors of extreme Earth-like planets can be used as a first characterization when prioritizing exoplanets for spectroscopic follow up. We build a strong interdisciplinary link between geomicrobiology and observational astronomy, by exploring the color signatures of extremophiles as well as the various extreme niches that those organisms inhabit on Earth. In addition, we provide the first database of surface signatures of terrestrial life for a broad range of pigmented microorganisms, including ones isolated from Earth’s most extreme environments. Our spectral library provides a broader and more realistic guide for the search for surface features of extraterrestrial life. The work presented in this thesis provides a first step toward characterizing a second Earth, in preparation for the next generation of space- and ground-based instruments, which will increase the chances of detecting life.