An Ancient Mystery: How Old Are Saturn's Rings?

The rings of Saturn have dazzled humans ever since they were spotted by Galileo, but they still contain many unexplained mysteries, such as how old they are. One theory states that they date back approximately 4.6 billion years; another suggests that they’re just 100 million years old.

Scientists backing the younger theory contend that the rings should show more evidence of space debris from the Kuiper Belt, which would make them darker than they appear today. Proponents of the older view note that the rings were probably created by a moon or some other icy object falling apart as it passed close by Saturn, an event which doesn’t seem to have happened in recent times (“recent” in astronomical terms, at any rate).

Some of the trouble comes from not knowing precisely how massive the rings are—a lighter series of rings could have formed more recently than a heavier one.

The case may be solved by the Cassini space probe, which is scheduled to fly between Saturn and its rings in September 2017 on the last leg of its mission. Once inside the rings, researchers can measure the gravitational pull on Cassini from both directions, Saturn on one side and the rings on the other, then compare those figures with earlier data about gravitational pull from outside the rings. According to the website, Science News, researchers have a betting pool on the findings.