The sources of molecular water in planetary systems is a subject of general interest in astrophysics and astrochemistry and its presence and persistence are critical for space missions involving long term human exploration. The Moon is the nearest exploration target and sources of water include primordial water, delivery via comets and meteorites, formation and release during small impact events, and solar wind interactions. An additional source term of molecular water is the thermally activated process known as recombinative desorption (RD) or associative desorption (AD) from lunar regolith grains. This involves hydroxyl (-OH) defects that were made by implantation of solar wind protons. Using several Apollo lunar samples, temperature program desorption (TPD) experiments conducted under ultra-high vacuum conditions yielded first order activation energies for desorption of chemisorbed molecular water and second order activation energies for the RD mediated formation and release of molecular water. Depending on the temperature excursions, RD can occur on a diurnal basis and is likely prevalent during impacts with meteorites and meteoroids. Once formed, the water can either desorb, or be transported on and within the regolith. Our combined experimental and modeling effort has successfully simulated recent observational data. Water formation via RD is likely general under astrophysical conditions that involve proton bombardment followed by thermal excursions ( > 400 K), and is critical to developing strategies for extraction of water for future, sustainable human space exploration missions.