Titan Ethane Still Missing, and Other Planetary Puzzles
We update the problem of Titan’s missing ethane and other challenges to billions of years.
Titan: Where’s the Ethane?
Calculations of ethane production in the 1990s led to predictions of a global ocean of ethane by irreversible processes driven by the solar wind. The Huygens Probe (2005) falsified that prediction, but there should be some at least. Here’s the latest bad news posted by Astrobiology Magazine, based on a new study of the second-largest lake on the giant moon of Saturn:
“Before Cassini, we expected to find that Ligeia Mare would be mostly made up of ethane, which is produced in abundance in the atmosphere when sunlight breaks methane molecules apart. Instead, this sea is predominantly made of pure methane,” said Alice Le Gall, a Cassini radar team associate at the French research laboratory LATMOS, Paris, and lead author of the new study.
A number of possible explanations could account for the sea’s methane composition, according to Le Gall. “Either Ligeia Mare is replenished by fresh methane rainfall, or something is removing ethane from it. It is possible that the ethane ends up in the undersea crust, or that it somehow flows into the adjacent sea, Kraken Mare, but that will require further investigation.”
Deputy lead Steve Wall tried to smile about this as he said, “Titan just won’t stop surprising us.”
Update 5/08/16: Icarus just published another paper called, “Titan’s Missing Ethane.” The abstract states that 1.37 million cubic kilometers of liquid ethane should have been produced throughout the assumed age of the moon. Since the surface area is 80 million square kilometers, simple division yields a layer 0.017 km deep—a global ocean roughly 56 feet all over the moon. (Note: that’s far less than previous estimates that predicted half a mile deep.) Where is it? Their only suggestion is that somehow it sank into the icy crust where it cannot be observed. Why didn’t the methane sink, too? The abstract doesn’t mention any conceivable sorting action of a porous crust to explain why methane is found in large polar lakes, but almost no ethane. From that puzzle, Gilliam and Lerman go hydrobioscopic, distracting attention to the possibility of life. Sadly for them, that’s bad news, too. “The temperatures on Titan, much lower than on primordial Earth, are less favorable to the ‘Second Coming of life’ on Titan.” Never seen that phrase in print before.
Mercury’s Carbon Footprint
The innermost planet will transit the sun Monday May 9, a rare event that occurs 13 times a century on average (last was in 2006, for history, read David Rothery’s piece on The Conversation; Space.com describes how to see it safely, and what to expect). A paper in Nature Geoscience says that the crust is darker than predicted. They infer an “ancient carbon-bearing crust” formed “via impact processes or assimilation of carbon into rising magmas during secondary crustal formation.”
The Moon’s Delicate Pas de Deux
A paper in Icarus exposes problems with moon formation theories. Factors had to be delicately balanced for a molten Earth and Moon to arrive at their final destinations while maintaining the currently-observed lunar inclination. The timing of solidification is critical, Nimmo and Chen say; “There is thus a ‘speed limit’ on how fast the Moon can evolve outwards while maintaining its inclination.” Either the early Earth had to be 1-2 times less dissipative than it is now, or else the moon’s inclination had to rise after it passed through a critical “Cassini state transition” at 30 Earth radii. This “requires subsequent late excitation of the lunar orbit after the crystallization of the lunar magma ocean.” How did that happen? If the Earth and Moon did not evolve from a molten state, as current theory assumes, the puzzle could be circumvented.
Ceres Bright Blue Craters
Astrobiology Magazine posted pretty pictures from the Dawn spacecraft, still orbiting the largest asteroid Ceres. Haulani Crater has a strange polygonal shape, while smaller Oxo Crater, second brightest feature on Ceres, displays a prominent slump along one rim. Hualani “shows rays of bluish ejected material. The color blue in such views has been associated with young features on Ceres.”
Jupiter Jekyll and Hyde
JPL scientist Kevin Grazier, who appeared briefly in The Privileged Planet, has run computer models for years to show that Jupiter may not be Earth’s protector after all. Comets and asteroids, he shows in his paper in Astrobiology, are just as likely to be deflected toward the Earth as away from it. He spins this as fortuitous in that the impactors “deliver life-enabling volatiles to the terrestrial planets.” Meanwhile, Icarus posted a paper dealing with the problem of the high mountains on Jupiter’s volcano moon Io. More falsified expectations were expressed in Astrobiology Magazine about Jupiter’s moons, particularly the smooth-cracked Europa: “[Scientists] had expected to see cold, dead places, but right away they were blown away by their striking surfaces” says a faculty member at Columbia. Carl Wunsch, meanwhile, deals with global ice-covered worlds in a paper on Icarus. “Little can be said concerning a reduction in tidal dissipation necessary to avoid a crisis in the history of the lunar orbit,” but he said it anyway.
Saturn: Y Is Enceladus Young?
Space.com shows a mysterious Y shape of ridges on Saturn’s geyser moon Enceladus. “Such features are also believed to be relatively young based on their lack of impact craters — a reminder of how surprisingly geologically active Enceladus is,” Cassini scientists said. Other Y shapes are seen along the ends of the south pole “tiger stripes” where the geysers erupt. A video clip explains the little moon’s surprises. “The surface of Enceladus is believed to be possibly less than 100 million years old, which would make it one of the youngest surfaces in the solar system.” If so, “possibly less” could imply “a lot less,” considering that 100 million years is 1/45th the assumed age of the planets. Another piece on PhysOrg tries to account for the heat by tidal friction. Because eruptions on Earth don’t last very long, scientists are rushing to a new theory by Kite and Rubin like drowning victims to a ring buoy. “It’s a puzzle to explain why the fissure system doesn’t clog up with its own frost,” one scientist said. “And it’s a puzzle to explain why the energy removed from the water table by evaporative cooling doesn’t just ice things over.”
Update 5/08/16: Cassini scientists watched the plume occult a star recently, according to Astrobiology Magazine. The headline reads, “Enceladus jets: surprises in starlight” because some of the jets (but not all) seem to blast out with increased fury when the moon is at apoapse, its farthest point from the planet. [The observations, by the way, were made by Voyager veteran Candy Hansen, who appears in the bonus features of Illustra Media’s film The Privileged Planet.] Like today’s Icarus paper on Titan’s ethane, NASA’s leaps into hydrobioscopy, using the power of suggestion, to claim without any observational justification:
Exactly how or why that’s happening is far from clear, but the observation gives theorists new possibilities to ponder about the twists and turns in the “plumbing” under the moon’s frozen surface. Scientists are eager for such clues because, beneath its frozen shell of ice, Enceladus is an ocean world that might have the ingredients for life.
Special Pleading at Dione
Meanwhile, there are puzzles at Saturn’s fourth moon Dione. A paper in Icarus finds crater rays that are very bright, so much so that “the implantation event occurred very recently.” The rays extend over much of the moon and would normally be darkened in short order by the solar wind.
Phoebe Ring Update
A new paper in Icarus updates knowledge about Saturn’s largest ring, the surprising Phoebe Ring discovered by Cassini, which orbits retrograde around the planet (10/07/09). This “vast debris disk” extends from 80 to 260 Saturn radii. If as assumed, “the Phoebe ring is generated through steady-state micrometeoroid bombardment” of Saturn’s outermost irregular satellites, why is there any material left? The small grains in the ring should be swept out of the ring by sunlight pressure in relatively short order. Could this process go on for billions of years?
Quick news from data trickling in from New Horizons:
- Pluto’s interaction with the solar wind appears to be unique (Astrobiology Magazine)
- Pluto’s “halo craters” are puzzling; see photo on Astrobiology Magazine. “Exactly why the bright methane ice settles on these crater rims and walls is a mystery; also puzzling is why this same effect doesn’t occur broadly across Pluto.”
- ‘Frozen Lake’ on Pluto May Point to a Warmer Time (Space.com): “Had New Horizon’s flyby taken place a few millions years ago, the tiny planet would have looked vastly different than it does today.” How about billions?
- Melodrama at New Scientist: “Pluto may have tipped over when Charon tugged at its heart.“
Makemake: The Hubble Telescope found a moon orbiting distant dwarf planet Makemake, reports Astrobiology Magazine. The moon is charcoal black, but Makemake is bright like fresh snow.
Planet Nine: Another Astrobiology Mag article says that Planet Nine, possibly awaiting confirmation, shouldn’t exist. “The evidence points to Planet Nine existing, but we can’t explain for certain how it was produced,” one planetary scientist says, without invoking some kind of planetary billiards knocking it out there.
Oort, Oort: Were you taught in school that the Oort Cloud contains pristine, primordial material? Then why does Science Magazine talk about “inner solar system material in the Oort Cloud”? No puzzle is immune from unbridled speculation. “We may be looking at fresh inner solar system Earth-forming material that was ejected from the inner solar system and preserved for billions of years in the Oort cloud.”
While we join the applause for these discoveries, and honor the high degree of intelligent design it took to obtain these images and data, we must remind everyone that scientific explanation differs greatly from scientific discovery. You can view the number of surprises that contradicted expectations as a rough index of explanatory success. The old planetesimal hypothesis is not doing very well. Look how many objects theory says shouldn’t exist! Since they do exist, consensus theory should cease from existing.