Exploring ExoPlanets: NASA's Future Space Missions

"There are infinite worlds both like and unlike this world of ours... We must believe that in all worlds there are living creatures and plants and other things we see in this world." Epicurus (c. 300 BCE) "Do there exist many worlds, Or is there but a single world? This is one of the most noble and Exalted questions in the study of Nature." Albertus Magnus, d. 1280. NASA planning for the discovery and exploration of "exoplanets", that is, planets around stars other than our own, has been underway for more than a decade. During that time, over 250 exoplanets have been discovered using ground-based techniques. Existing space assets such as the Hubble space telescope and Spitzer space telescope have been able to provide follow-up observations to characterize the planets and the systems they occupy. Inherent limitations of the available techniques and instruments have limited these discoveries to large planets in odd orbits. Still, these activities add significantly to our understanding of the nature of the investigations that will be required to characterize terrestrial, potentially habitable, exoplanets. We discuss the technology investments and accomplishments that have resulted from the early investments in NASA's exoplanet exploration program. A rich set of investigation types that now are at hand to probe exoplanet science is discussed. A new strategic pathway is discussed that, while constrained by budgetary realities in the federal process, promises progress with new smaller space missions to move this emergent field forward, and leading eventually to the flagship missions that will bring us the images and understanding of that "pale blue dot."