Glory Be Behind Saturn
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This is a view of Saturn we could never see from Earth. It’s the backside of the planet, with the sun shining through the rings. According to a JPL press release, “This marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on Sept. 15, 2006.” Another version with enhanced brightness and color is available also: click here for Saturn in all its backlit glory. This was Astronomy Picture of the Day for Oct. 16.
Look carefully in the outermost broad E-ring on the left foreground, and you can see the tiny moon Enceladus (click here for close-up) with its geysers sputtering along, feeding the short-lived E-ring with new material (11/28/2005, 03/01/2006, 07/11/2006). Now look at the picture again. See that tiny white speck on the left side, outside the bright main rings, but just inside the fainter G-ring? That’s the Earth – that’s us – from almost a billion miles away. Click here for a close-up. A member of a planetary discussion group has labeled the features in this image on Unmanned Spaceflight.
The Division of Planetary Sciences of the American Astronomical Society has been meeting all week in Pasadena, and scientific announcements are being made daily. One of the most interesting concerns Saturn’s rings. Scientists are baffled by color differences that cannot yet be explained. A JPL press release states:
“We expected to see things we haven’t seen before, but we are really, really puzzled by these new images of Saturn’s main ring system,” said Dr. Phil Nicholson, of Cornell, Cassini visual and infrared spectrometer team member. “The rings appear very different, with none of their usual calling card of water-ice features. There are hints that other material besides ice might finally be detected within the rings.”
“The main rings show a neutral color, while the C ring is reddish, and the D and E rings are quite blue,” added Nicholson. “We don’t quite understand if these variations are due to differences in particle size or composition, but it’s nice to be surprised every once in a while.”
The colors he mentioned can be seen in a labeled version of the montage, and are even more apparent in this infrared image. One reason for the puzzlement is that the images indicate the rings are dynamic, evolving, ephemeral phenomena. This means that what we are seeing today could not last for billions of years. New rings discovered in the backlit image seem associated with small embedded moons, indicating that the moonlets are producing the rings (see picture). How does this occur?
Saturn’s smallest moons have weak gravity and cannot retain any loose material on their surfaces. When these moons are struck by rapidly moving interplanetary meteoroids, this loose material is blasted off their surfaces and into Saturn orbit, creating diffuse rings along the moons’ orbital paths. Collisions among several moonlets, or clumps of boulder-sized rubble, might also lead to debris trails. For instance, Saturn’s G ring seems not to have any single moon large enough to see; it might have formed from a recent breakup of a moon.
Evidence for impactors also comes from the innermost D-ring of Saturn, another tenuous ring of fine material. Another JPL press release tells the detective story of a modern-day collision. A low-oblique Cassini image indicates a wavy, “corrugated” spiral with crests about 30 km apart (see illustration and line-of-sight diagram). In a Hubble 1995 photo, the crests were about 60 km apart. This indicates that the spiral has been winding up tighter over the last 11 years. Extrapolating backward, the scientists think a comet or meteoroid may have struck the ring back in 1984, producing waves like ripples in a pond. The waves wind up over time because of their orbits around Saturn – the inner parts moving faster than the outer parts.
More on the new Saturn ring discoveries can be found at the Cassini imaging team and Planetary Society websites. The DPS meeting announcements are also producing lively discussions on Unmanned Spaceflight. All three montage images can be found on JPL’s Planetary Photojournal. Another recent Cassini picture of Saturn shows cloud features like a string of pearls in Saturn’s upper latitudes. The spacecraft also found new ringlets within the Cassini Division, a gap in the main rings that was once thought to be devoid of material.
Cassini’s findings confirm predictions made over several decades now that Saturn’s rings are being rapidly eroded by collisions. We now have even more evidence that impactors, from comet-size to molecule-size, are wearing away Saturn’s rings. The E-ring would be gone in mere decades or centuries if Enceladus were not constantly replenishing with new micron-size material. The color differences between the rings also show that whatever non-ice material has been added has not had time to become thoroughly mixed. And it would be surprising to think that this new D-ring impact was a one-time phenomenon we just happened to be lucky to witness.
It may be impossible to say from data alone that the rings are mere thousands of years old or less, but they certainly cannot be billions of years old. That should raise some eyebrows by several inches among scientists who accept the standard A.S.S. (age of the solar system) as being 4.5 billion years old. Upper limits at ring ages are often put at 10 or 100 million years. That may sound like a lot (it’s an upper limit, remember), but even 100 million years is 1/45 the standard age. What was Saturn doing the other 44 parts? No materialist wants to believe that humans were somehow lucky to emerge right at the time when Saturn’s rings were at the height of their glory. Yet no secular scientist dares question the A.S.S., because concluding a recent formation of Saturn and the rings would collapse the time available for evolution. There is nothing about the Saturn system that needs billions of years. A scientist should follow the evidence where it leads, whether or not it agrees with prevailing orthodoxy.
Those of us living in 2006 should take time to value the privileges we have in this age of discovery. Pictures like this are hard to come by. It took over 3 billion dollars, and hundreds of scientists and technicians, to build the Cassini spacecraft. This complex machine had to fly for seven years before even getting to Saturn, and has orbited over two more years before getting into position last month to look back toward home and take this unprecedented shot. In 1609, when Galileo Galilei first turned a crude telescope to the sky and beheld new and wonderful things – including the rings of Saturn for the first time – his response was to worship the Creator. He said, “I render infinite thanks to God for being so kind as to make me alone the first observer of marvels kept hidden in obscurity for all previous centuries.” What is your response as you look at this rare vantage point on creation?