Tthe Kuiper Belt is a region of the Solar System that lies beyond the orbit of Neptune and is populated by a large number of small, icy bodies. The Kuiper Belt is thought to be the source of comets that are occasionally seen in the inner Solar System.
Examples of spacecraft that have studied the Kuiper Belt include NASA's New Horizons spacecraft, which flew by Pluto, a Kuiper Belt object in 2015, and the European Space Agency's Rosetta spacecraft, which studied the comet 67P/Churyumov-Gerasimenko, which is thought to be a remnant of the Kuiper Belt. NASA and other space agencies have proposed missions to explore other objects in the Kuiper Belt and study the region in more detail, such as the proposed Lucy and Psyche missions.