https://phys.org/news/2018-07-possibility-moon-life.html

Schulze-Makuch and Ian Crawford, a professor of planetary science and astrobiology at the University of London, say conditions on the lunar surface were sufficient to support simple lifeforms shortly after the Moon formed from a debris disk 4 billion years ago and again during a peak in lunar volcanic activity around 3.5 billion years ago.

During both periods, planetary scientists think the Moon was spewing out large quantities of superheated volatile gases, including water vapor, from its interior.