The Ultraviolet and Visible Spectrometer (UVVS) on the MESSENGER spacecraft observed three large transient events on Mercury’s nightside “tail,” during which exospheric brightness increased by an order of magnitude. UVVS observed enhancements of atomic sodium vapor, and, in one event, atomic sodium, magnesium, and calcium. Meteoroid impacts are the most likely source given that the events can be simulated with instantaneous injections of vapor. Models for the three events are included in an attached ASCII file along with the original observations. The data consists of atomic emission time series recorded by the UVVS as its sightline was scanned back and forth across Mercury's nightside. Individual data points consist of UTC observation time and radiance in units of kilorayleighs. Each event is labeled by its atomic species and year of occurrence (2011, 2012, or 2013). Another ASCII file has steady-state simulations that capture typical exospheric behavior. Models and data are described in Cassidy et al. (2021): https://doi.org/10.3847/PSJ/ac1a19. More information on the original data is available at the NASA Planetary Data System. See data product ID MESS-E/V/H-MASCS-4-UVVS-DDR-V1.0. Videos (MPEG-4 format) of the best-fit models are also included. The perspective is looking northward from below Mercury’s southern hemisphere. The UVVS field of view—a slit oriented along the sun-Mercury line—is shown as a white stripe. The sun is on the left. Note that for the 2011 event, the initial outburst of vapor is in complete darkness. The atoms are not visible until they reach Mercury’s penumbra.