If you want to see Saturn’s rings, you'd better make it quick. A new study suggests they will be gone in about 1 billion years, or roughly a quarter of the remaining life of the Sun.
But the good news is that this appears to be about 10 times longer than we thought they were going to last, with previous estimates coming in at around 100 million years.
The finding was published in a paper in the journal Icarus, with the team of researchers led by William Farrell from NASA’s Goddard Space Flight Center in Maryland.
To make their findings, they used data from the Cassini spacecraft. When it arrived in orbit in July 2004 and made its Saturn Orbit Insertion (SOI), it swept over the main and brightest of the rings, the B ring. This provided a unique opportunity to get unique plasma data using its Radio and Plasma Wave System (RPWS) instrument.
Saturn’s rings are gradually losing their material. From the flyby of the Voyager 1 and 2 spacecraft in 1980 and 1981, it was thought that this was due to interstellar debris hitting them, creating plasma and releasing gas.
Cassini, however, found that the plasma does not seem to be caused by impacts, but rather from the light of the Sun causing a photolytic process. This is creating the plasma, which produces negatively charged electrons that are an indicator of ring loss.
This is a much more “passive” method of ring loss than meteor impacts, suggesting that the rings will survive much longer than previously thought.
“Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend [one billion] years, and that there is limited evidence for prompt destruction (loss in less than 100 million years),” the team writes in their paper.
And we might soon know for certain if this new theory is correct. Cassini is currently performing a series of 22 dives between Saturn and its rings, the closest a spacecraft has ever been to the planet.
Using its Radio and Plasma Wave System (RPWS) instrument, Cassini will send back invaluable data that could tell us for certain just how long Saturn’s rings have left.
“This set of SOI observations, together, point to a shift in thinking about space environmental ring loss,” the team concluded. “That it is not driven by an energetic impact process or instabilities, but instead is driven primarily by more passive photolytic processes.”