https://www.vice.com/en_us/article/88gpk3/all-four-building-blocks-of-dna-have-been-found-in-meteorites

For the first time ever, all four major components of DNA, the biological blueprint of living things, have been detected in rocks from outer space, a discovery that suggests the building blocks of life may have been delivered to Earth by ancient extraterrestrial objects, according to a new study.

DNA is a helical structure made of so-called “nucleobases”—the compounds adenine, guanine, cytosine, and thymine—which combine in motley permutations to write the source code for life on Earth, including humans. Though adenine and guanine were found in meteorites about 50 years ago, the presence of cytosine and thymine in these extraterrestrial objects has remained elusive, despite evidence that the compounds might have existed in the primordial interstellar dust that gave rise to our solar system some 4.6 billion years ago.