For as long as humans have looked up at the night sky, we've wondered who, or what, might be looking back.
From ancient myths about gods descending from the heavens to 20th-century UFO sightings and today's hunt for exoplanets, the question of whether we are alone in the universe has never stopped captivating us. From microbial fossils on Mars to interstellar comets to mysterious signals in deep space, there is a timeless curiosity around extraterrestrials.
