NASA revealed on Monday that it found evidence of water molecules on the sunlit side of the moon, which was previously thought to be impossible.

Scientists working with NASA’s Stratospheric Observatory for Infrared Astronomy, an airplane observatory, made the announcement in a teleconference with reporters. The discovery, using an infrared telescope on SOFIA, upends long-held theories regarding the surface of the moon. Previously, scientists thought that the absence of an atmosphere on the moon would cause any water present on a sunlit surface of the moon to evaporate into the cosmos.