Cosmic rays are charged, high-energy particles that move through space at near-light speed. Every second, every square meter of Earth’s atmosphere is pelted by large quantities of cosmic rays. These particles are usually hydrogen nuclei, or protons. But scientists have detected examples of other subatomic particles like neutrons, electrons, and even antimatter. NASA’s Super Trans-Iron Galactic Element Recorder (SuperTIGER), a balloon-borne instrument, detected cosmic rays composed of the nuclei of heavier atoms, like cobalt or barium.