Final answer:
Uranus' rings consist of small, dark particles, likely made of carbon and hydrocarbon compounds, trapped within the orbits of small moons that may have originated from broken-up moons.
Step-by-step explanation:
Uranus' rings are composed of micrometer to meter-sized particles darkened by radiation and trapped among the orbits of small moons. These particles are nearly as black as lumps of coal and primarily consist of carbon and hydrocarbon compounds. Much like similar organic materials found in the outer solar system, the dark, tar-like substances are also present in many asteroids and comets. These particles are likely remnants of one or more of Uranus's small moons, given their similar composition, which may have broken apart to form the rings. Unlike Saturn's ice-filled rings, the rings of Uranus contain significantly less mass and are confined to a few narrow, dark rings with broad gaps in between.
Furthermore, the complex structure within these rings can be attributed to gravitational resonances and the shepherding effect of small moons, like Cordelia and Ophelia for Uranus's Epsilon Ring. Despite the information gathered, the exact origin and age of Uranus's ring particles remain a mystery to astronomers.