Since the beginning of civilization, humanity has wondered whether we are alone in the universe. As NASA has explored our solar system and beyond, it has developed increasingly sophisticated tools to address this fundamental question. Within our solar system, NASA’s missions have searched for signs of both ancient and current life, especially on Mars and soon, Jupiter’s moon Europa. Beyond our solar system, missions, such as Kepler and TESS, are revealing thousands of planets orbiting other stars. The explosion of knowledge of planets orbiting other stars, called exoplanets, and the results of decades of research on signatures of life - what scientists call biosignatures - have encouraged NASA to address, in a scientifically rigorous way, whether humanity is alone. Beyond searching for evidence of just microbial life, NASA now is exploring ways to search for life advanced enough to create technology.
