The possibility of extraterrestrial life has always fascinated humans. People have speculated about alien life on Mars and other nearby planets ever since we realized they were different from the other points of light in the night sky. Today, even though our technological capabilities have allowed us to study those worlds up close and even peer at (and listen to) planets around other stars, we still don’t have a concrete answer to the question of whether we are alone in the Universe. The lack of evidence of life beyond Earth doesn’t mean we don’t have any idea what could or should be out there. The more we learn about the Cosmos — from the planets and moons in our Solar System to the great expanse beyond — the more confident we become that alien life must be out there. Lots of people believe in aliens, although this belief tends to be based on movies and UFO claims. But science provides insights for the likelihood that we’re not alone in the Universe, and can answer some of the biggest questions people might have about what kind of life is most likely to actually be out there.