Most of our experience with the Search for Extraterrestrial Intelligence (SETI) has been focused on capturing radio signals that alien species have sent out, whether intentionally or unintentionally. That creates a huge “synchronicity” problem - what if there aren’t any alien civilizations broadcasting radio signals now, but there were a billion years ago? The Milky Way is around 13 billion years old - hoping that we exist at the same time as an alien civilization that happens to be actively messaging is a huge leap of faith. But, according to a new paper available in pre-print on arXiv and submitted to the International Journal of Astrobiology by Lewis J Pinault, as associated researcher at the SETI Institute, and his co-authors, we could take a completely alternative approach to trying to find alien civilizations - by looking for evidence of them in lunar dirt.