The famous ring system of Saturn may be much older than some planetary scientists think, according to a new study published in the journal Nature Astronomy.
NASA’s Cassini spacecraft in orbit around Saturn. Image credit: NASA / JPL-Caltech.
Southwest Research Institute researcher Luke Dones and his colleagues from CNRS and the University of Colorado Boulder take a closer look at recent data from NASA’s Cassini spacecraft that inspired several research papers suggesting that the rings were formed between 10 million and 100 million years ago.
Those studies challenged long-held models that put the formation of the rings several billion years earlier, around the time Saturn formed with the rest of the Solar System.
“The historic models probably had it right in the first place,” the scientists said.
The debate focuses on Cassini data from 2017, when the orbiter revealed a trove of data with dazzling images of Saturn’s rings, which are composed of almost pure water ice.
“After Cassini’s mission ended, there was a small flood of research that claimed the rings were much younger than we had considered them to be,” Dr. Dones said.
“A common argument was that the rings, if much older, would have become much more polluted as a result of meteoroids crashing into them.”
A series of studies suggested that the rings would have absorbed portions of dark, dusty material from the meteoroids and gradually become darker.
Therefore, the rings would be too bright and clean to have existed in the Solar System for billions of years.
According to the team, Cassini measurements show the rings are constantly losing matter to Saturn. This process could very well be ‘cleaning’ the ice of the rings and making them brighter over time.
“One of the clearest indications that the rings are old is that their mass is consistent with current understanding of how primordial rings change,” Dr. Dones and co-authors said.
“Rings spread with time, spawning satellites at their outer edge and losing mass to Saturn at their inner edge.”
“More massive rings spread faster, so even a very massive primordial ring would be expected to now have the present mass of the rings.”
“If the rings are young, then their current mass would have to be a coincidence.”
“It’s not impossible to determine the age of the rings, but to do so we’ll need a future mission to Saturn that spends a long, intense period studying the rings themselves as well as the relationship between them and the gas giant,” Dr. Dones concluded.
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Aurélien Crida et al. Are Saturn’s rings actually young? Nature Astronomy, published online September 16, 2019; doi: 10.1038/s41550-019-0876-y
