Final answer:
Enceladus, an icy moon of Saturn, continuously replenishes Saturn's E Ring with ice particles through geological activity. The water ice originates from cryovolcanic emissions, supporting the presence of the ring.
Step-by-step explanation:
The rings of Saturn are primarily composed of water ice of different sizes. A significant source of this water/ice in Saturn's E Ring is believed to be the icy moon Enceladus. Through geological activity, Enceladus releases ice particles that contribute to replenishing the E Ring. These particles emerge from the moon's south polar region, where cryovolcanism occurs—jets of water vapor and ice are emitted from fractures in the icy surface. This continual replenishment suggests Enceladus as a source of the water/ice in the rings
Additionally, the origin of planetary rings can be theorized by two hypotheses: the breakup hypothesis, which posits that rings form from the shattered remnants of a moon, and the failed moon hypothesis, which suggests that the material in the rings never coalesced into a moon initially.