Cassini Gets Higher Look at Saturn's Youth
Now entering its final dramatic high orbits, the Cassini spacecraft is finding unexpected things for an assumed old planet, Saturn.
Cassini is starting a busy last year in orbit around Saturn (Space.com). As planned, mission navigators at JPL have set Cassini’s course for a series of high-inclination orbits that will take the spacecraft closer than ever to the rings (Phys.org). Then, in April, comes the Grand Finale: the craft will make 22 risky high dives into a 1,500-mile gap between Saturn and the D ring, providing unprecedented views of the rings from above and below (National Geographic; see orbit diagram on Space.com). If Cassini survives, mission controllers will send the history-making craft to its death, plunging it into Saturn itself in September, 2017 (see NASA/JPL video clip at Space.com or National Geographic). It will have been in orbit for 13 years since its main engines burned on June 30, 2004, allowing Saturn’s gravity to capture it, initiating years of complex maneuvers and amazing discoveries about Saturn, its magnetic field, its moons, and the planet-sized moon Titan.
The initial ring-grazing orbits began on November 30. On December 6, NASA released the first images from high over Saturn’s north pole, giving the best-ever views of the mysterious hexagon—a pattern of standing waves in the atmosphere embedded with cyclonic storms (good reproductions on Astrobiology Magazine). But for “Saturn, the bringer of old age,” as Gustav Holst called it in his famous orchestral suite The Planets, some things about Saturn appear quite youthful.
Take the steep-walled canyons on Titan (Phys.org). Nobody expected canyons 800 to 1,900 feet deep, half a mile wide, with steep walls, filled with hydrocarbons at their floors. Scientists were floored themselves, because the implications defied billions of years:
“The canyons found in Titan’s north are even more surprising, as we have no idea how they formed. Their narrow width and depth imply rapid erosion, as sea levels rise and fall in the nearby sea. This brings up a host of questions, such as where did all the eroded material go?” Hayes said.
Project leader Valerio Poggiali attempted explanations, but without much success:
“It’s likely that a combination of … forces contributed to the formation of the deep canyons, but at present it’s not clear,” Poggiali told the Jet Propulsion Laboratory, the group managing Cassini. “What is clear is that any description of Titan’s geological evolution needs to be able to explain how the canyons got there.“
See also a study of Titan’s alluvial fans published in Icarus based on Cassini radar maps. Cartwright and Burr compared them with alluvial fans in Death Valley, finding some similarities, but important differences, too—possibly due to Titan’s lower gravity and different composition. Importantly, “fan-like features may result from non-alluvial processes, such as form distributary fluvial systems on Earth.” When liquids move, things happen. Material moves. Have they been moving for billions of years?
Even Fox News caught the surprised expressions of Cassini scientists when the word got out: “Surprise! Saturn’s rings may be far younger than originally thought.” Actually, ringmasters have suspected the rings cannot be billions of years old for quite awhile now. James Clerk Maxwell (our Creation Scientist of the Month) had figured out in 1857 that the rings could not be solid or liquid structures, but had to be composed of small, independently orbiting bodies. That was confirmed by the first flybys of Pioneer and Voyager in the 1970s and 1980s. As the ringmasters thought about the erosional effects on the rings, and how bright they remained after billions of years of pollution by space dust, they came to the conclusion the rings had to be far younger than Saturn—perhaps 10 or 100 million years (1/450th or 1/45th the age of the planet). That raises the question of what kind of process could make the rings when Saturn was already an old-timer (according to conventional wisdom). New revelations show that, indeed, they are too bright to be old.
“Younger than thought” is a trending phrase. Science Daily illustrates this: “Saturn’s bulging core implies moons younger than thought.” Newtonian physics requires that tidal forces push the moons away over time. Cornell astronomer Radwan Tajeddine performed a new computation of two factors, elasticity and dissipation, based on actual data of 4 inner moons, and concluded that they cannot be billions of years old.
Tajeddine explains that if Saturn moons actually formed 4.5 billion years ago, their current distances from the home planet should be greater. Thus, this new research suggests, the moons are younger than 4.5 billion years, favoring a theory that the moons formed from Saturn’s rings.
The team also found that Saturn moon Rhea is moving away 10 times faster than the other moons, which is the first evidence that a planet’s dissipation factor can vary with its distance in relation to the moon. The scientists have no definitive explanation.
Another paper in Icarus fails to find a long-age solution to Saturn’s geysering moon Enceladus. There just isn’t enough heat to keep liquid under the ice that can power the geysers erupting through the moon’s south polar cracks. Kamata and Nimmo find that the requirements are an order of magnitude higher than what Cassini has measured.
Recent geodetic measurements for Enceladus suggest a global subsurface ocean that is thicker beneath the south pole. In order to maintain such an ocean, viscous relaxation of topography at the base of the ice shell and melting of ice need to be balanced. In this study, we investigate the interior thermal state that can lead to the relaxation timescale being comparable to the melting timescale. Our results indicate that a basal heat flux about ten times higher than that due to radiogenic heating, or an ice shell tidal heating rate about ten times higher than the conventional estimate of 1.1 GW [gigawatts] is necessary if the ice shell is in thermal equilibrium. These requirements are concordant with recent astrometric studies.
The fight is on between the predictions of the moyboys and the Real Saturn. Now for the Grand Finale!
Your faithful editor/reporter watches all this with interest from home. He would still be working as part of the team alongside the scientists if it had not been for the intolerance two snowflakes. These two ladies, close friends with each other, could not tolerate the thought of intelligent design. It made them “uncomfortable.” So in the name of tolerance, they got my boss, the Human Resources Department and ultimately JPL’s lawyers to get rid of me after 14 years of employment, 9 of them as a Team Lead. We took them to court, but a Democrat-appointed judge agreed with JPL’s bias, and ruled against me with no explanation. You can read about it here. Cassini’s discoveries, however, are public knowledge, and I take some satisfaction in finding the “tolerant” bunch completely baffled by what they are discovering.