The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time. These particles can escape the Sun’s gravity because of their high kinetic energy and the high temperature of the corona. Three years ago University of Tennessee, Knoxville, researchers helped to discover water on the surface of the moon. Now, they are piecing together the origin of that water: solar wind. A new study published in this month’s Nature Geoscience confirms solar wind as a source for water embedded in the lunar surface.