Information gleaned form Cassini, Galileo and New Horizons missions seems to indicate that ripples seen in the rings of Saturn and Jupiter were caused by comets. Shoemaker-Levy 9 (famous for a multiplicity of impacts on Jupiter in 1994) left one set of ripples. Saturn’s cometary clues date to a cloud of icy debris passing through the inner rings in 1983.
“What’s cool is we’re finding evidence that a planet’s rings can be affected by specific, traceable events that happened in the last 30 years, rather than a hundred million years ago,” said Matthew Hedman, a Cassini imaging team associate, lead author of one of the papers, and a research associate at Cornell University, Ithaca, N.Y. “The solar system is a much more dynamic place than we gave it credit for.”
Well, I suspect that was already suspected … how likely is it that the rings around these large planets were formed billions or even millions of years ago and have remained untouched? Clearly, they must reform and even re-accrete material over time as varoius snowballs and rocks mess them up now and then.
But, knowing the details is interesting and important, and it is rather impressive that we can see decades old evidence. This may mean that multiple ancient (but how ancient we do not know) events can be reconstructed by studying the rings:
“We now know that collisions into the rings are very common – a few times per decade for Jupiter and a few times per century for Saturn,” Showalter said. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”
The ripples also give scientists clues to the size of the clouds of cometary debris that hit the rings. In each of these cases, the nuclei of the comets – before they likely broke apart – were a few kilometers wide.
“Finding these fingerprints still in the rings is amazing and helps us better understand impact processes in our solar system,” said Linda Spilker, Cassini project scientist, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Cassini’s long sojourn around Saturn has helped us tease out subtle clues that tell us about the history of our origins.”
Read the whole press release, find out about the published papers, and see the pretty pictures here.