Rock and dust samples retrieved by NASA from the asteroid Bennu exhibit some of the chemical building blocks of life, according to research that provides some of the best evidence to date that such space rocks may have seeded early Earth with the raw ingredients that fostered the emergence of living organisms.

Japanese scientists detected all five nucleobases — building blocks of DNA and RNA — in samples returned from asteroid Bennu by NASA’s OSIRIS-REx mission. NASA’s OSIRIS-REx mission brought back 121.6 grams of asteroid Bennu,