April 30, 2013 | David F. Coppedge

Saturn's Rings Impacted by Meteoroids

Cassini has observed clouds of dust from meteoroids hitting the rings.  The data will “impact” theories of the rings’ origin and age.

New observations have shown dust clouds from four impacts on Saturn’s rings (see JPL press release).  One impact was observed twice, about 25 hours apart.  The impacts were found in all three major rings: A, B, and C.  The ejecta clouds are thought to have been observed between 1 and 50 hours after the impacts.  According to National Geographic, streams of meteors must be hitting the rings more often than thought.  A paper by Cassini scientists was published in Science Magazine.

National Geographic waxed philosophical, saying, “The hope in the science community is that insights into these ring impacts may also shed light on the rings’ puzzling origins.”  That sentence cloaks the real problem: impacts are destructive, not constructive.  Jeff Cuzzi, long time ringmaster and co-author of the paper, expressed concerns in the press release:

Saturn’s rings are unusually bright and clean, leading some to suggest that the rings are actually much younger than Saturn,” said Jeff Cuzzi, a co-author of the paper and a Cassini interdisciplinary scientist specializing in planetary rings and dust at NASA’s Ames Research Center in Moffett Field, Calif. “To assess this dramatic claim, we must know more about the rate at which outside material is bombarding the rings. This latest analysis helps fill in that story with detection of impactors of a size that we weren’t previously able to detect directly.”

The impactors are estimated to be between a centimeter and several meters in diameter.  If a rain of dusty debris like this has been going on for billions of years, the rings should appear darker than they are.  Furthermore, since they carry away more mass than they add, they have been eroding the rings for a long time according to current beliefs about Saturn’s age.  Pollution and erosion are not helping keep Saturn’s rings old.

Another clue for a high impact rate is the “ring rain” that descends onto Saturn’s equatorial bands.  Science Daily said that “more charged particles fall than thought” from water ions originating in the rings.  Are the charged particles coming from impacts hitting the rings?  What other process could be sending material from the rings onto Saturn?  The article didn’t say.  In any case, this is another erosive process, it appears.

The paper in Science said that the estimated impact rate, though significantly higher “at face value” than before, is too uncertain to know for sure:

Our results are higher than the extrapolation by one or two orders of magnitude (Fig. 4); at face value, especially if this increase is also reflected in submillimeter-to-millimeter-size particles, then pollution and erosion rates due to interplanetary meteoroids might be higher than have been thought. However, gravitational focusing enhances the flux at Saturn’s rings by a factor of 4 to 40, and the sensitivity of rings to a two-directional flux yields another factor of 2, so our results may corroborate the previous extrapolation after all.

(By extrapolation, the authors refer to the prior habit of estimating impact rates for the outer solar system to be similar to rates in the inner solar system.)  Better observations to constrain the impact rate will be possible when the Cassini spacecraft approaches its end of mission (2017), when it is slated to make series of “high dives” over the rings and into the gap between the D ring and Saturn.

Update April 30:  Speaking of Saturn, an article on Science Daily attempted to explain away the planet’s “youthful appearance.”  Gas giants should darken with age, the article said, but Saturn is still light-colored.  By invoking some unobservable effects deep in Saturn’s atmosphere, some scientists at the University of Exeter were able to come up with a story for how the darkening influences were kept at bay.  Any hypothesis that is applied after the fact to only one planet of the solar system in order to explain an anomaly should be treated with skepticism.

If this were the only problem in the Saturn system facing the moyboys (believers in “millions of years, billions of years”), it would be worrisome for them.  But then you have Titan’s atmosphere, the Titan ethane problem, the Enceladus geysers, delicate rings, and other matters that, taken together, could title a book, “Billions of years: a theory in crisis.”  Prediction: future measurements of impact rates on Saturn’s rings will prove higher than expected.

 

(Visited 14 times, 1 visits today)

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.