Billions of years ago, our solar system coalesced within an interstellar molecular cloud, a nursery made up of gas and dust that clumped together to form stars, asteroids, and planets—eventually, our own Earth. Somewhere along that cosmic timeline, the amino acids that preceded life appeared. These molecules chain together to form the proteins responsible for nearly every biological function. But where those amino acids come from has been an enduring mystery. Did these biological building blocks somehow arise from the prebiotic conditions of early Earth, or was our planet seeded with these ingredients from elsewhere in the universe?