One of the greatest scientific questions is whether or not there exist inhabited worlds other than our own. The answer would inform not just our understanding of the formation of planets and of life upon them, but it would directly address the uniqueness of the Earth, and it would impact each individual's understanding of his or her place in the cosmos. Recently, astronomers have discovered many planets outside the Solar system that superficially resemble the Earth in size and in surface temperature. However, we know so little about these worlds that we cannot yet make informed statements about whether they are likely to be habitable. This initiative brings together astronomers, planetary scientists, atmospheric scientists, and geobiologists to pursue interdisciplinary research aimed at identifying and characterizing the closest habitable exoplanets and to facilitate the study of their atmospheres in the search for the chemical signatures of life. The impact of this work will be to cement a new discipline at the interface of our constituent academic communities and to chart the research path by which humans might learn whether there are inhabited worlds beyond the Earth.