Saturn's rings are disappearing. The James Webb Space Telescope may reveal how much time they have left.

An artist's impression of how Saturn may look in the next hundred million years. The innermost rings disappear as they rain onto the planet first, very slowly followed by the outer rings. (Image credit: NASA/Cassini/James O'Donoghue)

Saturn's rings are disappearing, and we don't know how much longer they will be around.

Astronomers have known since the 1980s that Saturn's icy innermost rings are steadily eroding onto its upper atmosphere. The downpour is happening at such a high rate that an Olympic-sized swimming pool of water rains on the gas giant daily. However, how quickly the iconic ring system is shrinking — which determines when it will vanish — continues to be an open question.