Today, the moon is about as inhospitable to life as it gets. The little water that’s there is trapped in ice or rock. It’s otherwise dry and airless, fluctuating in temperature by hundreds of degrees anywhere the sun shines. But long ago? That’s an entirely different story.

New research published in Astrobiology suggests that the moon may have been shockingly habitable in the past during at least two periods — shortly after the moon formed, and when volcanic activity was at its highest.