Mark Hammergren, PhD is an astronomer at the Adler Planetarium. His research interests include asteroids, comets, meteorites, and their effects on life on Earth, and the history and sociology of the flying saucer phenomenon. He directs the Astro-Science Workshop, a summer program for science-interested high school students currently in its 49th year, and cofounded the Adler’s Far Horizons citizen space exploration team.