Changing Stories at Saturn and Titan
News from the ringed planet and its largest moon shows scientists can’t keep their stories straight when trying to keep Saturn billions of years old.
Age of the rings: First they were old, then they were young, now they are old again. Mike Wall at Live Science claims that the “age of Saturn’s rings” has been “revealed.” The revelation was not inspired, though: “Saturn’s iconic rings likely formed about 4.4 billion years ago, shortly after the planet itself took shape, a new study suggests.” How, then, do they remain so pristine? How do they keep from grinding down to dust? How do they escape the constant bombardment of micrometeorites and atomic nuclei? Sascha Kempf (U of Colorado) bases his judgment on the low particle count coming from the Cosmic Dust Analyzer (CDA) for which he is a prime investigator. The extremely low hit rate (10-19 g/cm2-s-1) at 2 to 50 Saturn radii is “consistent with an old ring system,” he says – at least for the main rings. The article did not address how the more ephemeral D, F, G, and E rings are maintained, or how the rings survive other destructive processes like sputtering, collisional spreading, gas drag, and sunlight pressure. CDA only detects dust, not ions. For a primer on Saturn’s rings, see a feature on Space.com.
Tiny blip to moon factory: A barely-visible lump at the outer edge of the A ring is causing some to imagine Saturn as a modern moon maker. “A rebellious moon might have just popped out of Saturn’s rings,” Lisa Grossman wrote for New Scientist. Cassini scientists saw a disturbance that has quieted down. What does it mean? If a tiny “weird object” popped out, it’s too small to see – less than a kilometer wide. But they gave it the name “Peggy” anyway. This object (if it exists) might grow into a moon, they say, but then again, it might have been destroyed in a collision. They didn’t explain how a moon-growing process could go on for billions of years. If material is being lost from the rings continually, why is there a finite number of small moons, and where does new material come from to replenish what is lost?
Plasma in, plasma out: Remarkably, most of the plasma in Saturn’s magnetosphere comes from the little geysering moon Enceladus, when its water gets dissociated and swept into the magnetic field. That puts plasma in; what takes it out? The plasma content appears to be nearly in a steady state. An article on PhysOrg suggests that Saturn’s fast rotation sets up currents that sweep excess ions down the magnetotail. The article did not address the question of how long the tiny Arizona-sized moon Enceladus could feed the giant.
A hex on Saturn: A beautiful color movie of Saturn’s north polar hexagon made the news on Dec. 4 (see JPL press release). This atmospheric feature – unique in the solar system – is thought to form by standing waves in a jet stream, but there are mysteries. The nearest analogy mentioned is the ozone hole at Earth’s south pole, but most such features are “notoriously turbulent and unstable,” atmospheric scientist Andrew Ingersoll said. “A hurricane on Earth typically lasts a week, but this has been here for decades – and who knows – maybe centuries.” The images are clear enough to see “small vortices rotating in the opposite direction of the hexagon,” some as large as Earth hurricanes. A massive storm rotates at the center of the 220,000-mile-across feature. The south pole has a similar vortex, but no hexagon.
Titan swamped: Titan is Saturn’s largest moon. Keeping Titan old for billions of years requires erasing all the craters that should be there. Only 11 have been found for certain; another 50 are “potential” craters. Science Magazine tried various crater erasing theories. Sediments from mountain lakes? No; some craters are out in the plains. Wind-blown sand from the dunes? No; there’s no sand in the crater-free polar regions. Cryovolcanoes? Doesn’t explain why craters are in some regions and not others. Methane rain? Not fast enough to erase a large crater. The latest theory is that Titan has a methane-soaked, swampy surface hundreds of meters deep. Impactors would sink into the quicksand-like material, leaving no trace. There are exceptions, like well-preserved craters in the Xanadu lowlands (Titan’s oldest terrain), that require some ad hoc reasoning to explain. Maybe those craters were formed when the surface was dry, before the atmosphere formed. It’s convenient that none of those theory-rescuing factors are observable, otherwise someone might think Titan is young.
Glorifying Titan’s methane lakes: Titan’s north polar lakes made news on two fronts. For one, the radar mapper has a big enough composite picture to amaze viewers. Simon Redfern at The Conversation gave a nice write-up and picture, with video clip, of the latest buzz. See also coverage by the BBC News, New Scientist, and Jet Propulsion Laboratory. The other news comes from Cassini radar’s chance to ping the depth of one of the large northern seas named Ligeia Mare. Bounces from the bottom of the lake indicate it is 170 meters deep (like Lake Michigan) at most. Surprisingly, its radar transparency suggests it is filled primarily with methane (CH4), not ethane (C2H6) as expected. Though not nearly the global ocean once predicted, the lake is still a big container; nearby Kraken Mare is four or more times as large. “The total volume of the hydrocarbon Titanic seas corresponds to around 300 times that of Earth’s oil reserves, in a celestial body smaller than Earth,” Redfern said. (Titan’s diameter would just about cover the United States.) Space.com states the volume is estimated to be 2,000 cubic miles.
Still, that much fluid falls far short of the global ocean predicted:
Jeffrey Kargel, from the University of Arizona Tucson, pointed out that the presence of extensive methane seas and lakes at Titan’s north pole makes worse a long acknowledged deficiency of heavier hydrocarbons expected from models of Titan’s chemistry. Among them are ethane, ethylene, propylene, acetylene and benzene – heavy hydrocarbons generated as sunlight causes chemical reactions in Titan’s soup of natural gas.
(We’ve reported on the ethane deficit problem since before Cassini arrived at Saturn; search on Titan for entries.) Another puzzle, though, is how smooth the liquid surface is. Radar measurements show that there are no ripples higher than 1 millimeter. That’s as smooth as the paint on your car. This is surprising for a moon windy enough to form a belt of large sand dunes around the equator.
Titan get-together: The uncharacteristic size of Titan compared to all the other Saturn moons makes planetary scientists wonder how it got there. Science Now addressed the puzzles that Douglas Hamilton [U of Maryland] is trying to answer:
Titan is dominatingly big, having almost twice the mass of Earth’s moon and comprising 90% of the mass in orbit about Saturn. Titan is alone, orbiting in a million-kilometer gap bounded by tiny moons. And Titan’s orbit is odd: It is slightly elliptical rather than nearly circular and is tilted with respect to Saturn’s equator. With all those oddities, Hamilton said, “the biggest mystery is how it came to be in the first place.“
Hamilton’s latest proposal is that several small moons got together to form the giant. This would explain why there’s a gap. Assuming tidal interactions affected the collisions, it would also explain the strange orbit. To make it work, Hamilton has to assume the collisions were gentle, so the bodies would merge instead of splatter. It’s also ad hoc; “even Hamilton acknowledges he’s not sure how he would ‘prove’ that he is right.” How all that nitrogen and methane got into its atmosphere is for others to figure out.
Futures: Cassini has about 3 and a half more years to go before the end of its second extended mission. Planned observations include more Titan mapping, an Enceladus plume fly-through in August 2014, shots of Enceladus’s north pole, high-altitude studies of the rings, and as much science as the limited fuel will allow before the orbiter’s death plunge into Saturn in 2017. Having observed Titan since before its equinox, scientists are excited to watch for changes in the lakes and dunes as the Saturn system approaches northern solstice. Will the lakes migrate from the north pole to the south? Only time will tell.
In my 14 years’ experience on the Cassini team, I had the opportunity to meet and talk with many of the scientists, and hear them lecture, including Sascha Kempf and Andy Ingersoll. There is no question all the JPL scientists are extremely smart and talented at what they do. They got a bus-sized spacecraft to Saturn after all. They cannot see their bias, though, when it comes to dating things. The Age of the Solar System (A.S.S.) is a Law of the Misdeeds and Perversions, which cannot be altered (from Daniel 6:8). It’s not that these scientists are incapable of conceiving a younger age than 4.5 billion years, it’s that their brains have marinated in millions-and-billions language throughout their education and career, it never enters their minds to follow the evidence for youth honestly; the old age is a great Truth that they all Know. I’ve heard one of them say that he was trying to make Saturn’s rings last for billions of years for “philosophical reasons,” implying that the idea of young rings was repugnant to him.
Another factor is the “herd mentality” among scientists (see 12/09/13). These scientists all know each other. They meet at international conferences several times a year. They give presentations to one another. While there is some limited latitude for unique ideas that don’t stray from the A.S.S., there is no question that wanting to be liked and accepted by their peers is a factor in their behavior. None of them wants to hear his esteemed colleagues call out “boo” or indicate disgust with an idea too far outside the paradigm. This is how a consensus can form and persist despite powerful evidence against it. No ad-hoc scenario is too bizarre to prevent a kick in the A.S.S. And when you consider that youth of planets is often associated with the despised “young earth creationists,” none of them would ever dare to give aid and comfort to such “anti-science” outcasts. Evidence be damned; long live the consensus!
It appears hopeless to penetrate the dogma in this community, even if an individual here or there might be open to consider out-of-the-box ideas. Probably it will take a younger community doing a better job of explaining things outside the paradigm, over time as the old graybeards fade away. Meanwhile, we’ll keep reporting the news here, praising the good, pointing out the bad, and asking questions the paradigm never considers.
Research projects: (1) Calculate the volume of Titan’s lakes and see if the production rate of ethane can account for it in 4.5 billion years. Is there an upper limit? (2) Calculate the output of plasma by Enceladus and infer the water emission rate. What percentage of the moon’s mass would have to be ejected over 4.5 billion years? (3) Considering the rate of dust measured by the CDA instrument, what would be the maximum age of the rings?