Visiting an Exoplanet Author: Louis Friedman, Executive Director of The Planetary Society, Emeritus Description: There are two ways to visit an exoplanet — real and virtual. Real involves going there — something not possible now nor, except with extreme limitations, in the foreseeable future. Those limitations are with trips times of eons or with a one gram (or so) spacecraft to only the nearest star powered by a cost and politically prohibitive laser array. To visit a potentially inhabited exoplanet with extraterrestrial life will require searching over a large number of candidates probably within a distance of 10-50 times the distance to the nearest star, and a spacecraft 2-3 orders of magnitude larger. The spacecraft will also have to be capable of observing the exoplanet continuously for a while, rather than flying by it at an interstellar speed of (say) 1.5 AU/hour. But, fortunately, nature comes to the rescue – enabling virtual visits to exoplanets by remote observation using the solar gravity lens and positioning a spacecraft and its telescope along its focal line, beginning at 547 AU from the Sun. That is still a very tall order — but it can be done with today’s technology with a smallsat-solar sail combination and a trip time of 20-30 years. Such a mission has been under study for several years and is now the subject of a NASA Innovative Advanced Concepts Phase III study including the development of a technology demonstration mission to prove the smallsat-sail concept for high-speed exit of the solar system. The mission requires technology development — including lightweight electric micro-thrusters with a small RTG or nuclear battery, and multiple small spacecraft to enable a 1-2 meter optical telescope to operate in the solar gravity lens focal region. The resulting kilometer scale high-resolution of the exoplanet will enable seeing continents, large features, and even (should such exist) large scale evidence of life, as well as incredibly detailed spectral and compositional analysis of the atmosphere. No other scheme exists for such high-resolution observations, and it is possible even many tens of light-years from our Sun. It may be the only way to see life on another world.