  Cosmic rays are particles from the upper atmosphere which often leave bright
spots and trails in images from telescope CCDs. We investigate so-called ``fat"
cosmic rays seen in images from Vera C. Rubin Observatory and the Subaru
Telescope. These tracks are much wider and brighter than typical cosmic ray
tracks, and therefore are more capable of obscuring data in science images. By
understanding the origins of these tracks, we can better ensure that they do
not interfere with on-sky data. We compare the properties of these tracks to
simulated and theoretical models in order to identify both the particles
causing these tracks as well as the reason for their excess spread. We propose
that the origin of these tracks is cosmic ray protons, which deposit much
greater charge in the CCDs than typical cosmic rays due to their lower
velocities. The generated charges then repel each other while drifting through
the detector, resulting in a track which is much wider than typical tracks.
