Cosmic Whacks as Creative Forces
Asteroid impacts are some astronomers’ answer to everything, except when they are shown to be unworkable.
Titan as a billiard fusion: Most collisions break things up and send pieces scattering, but a new theory proposes that Saturn’s giant moon Titan represents a merger of moonlets. “Did several moons collide to form Saturn’s Titan?” Richard Kerr teased on Science Now. He heard that rumor at a meeting of the Division of Planetary Sciences (DPS) in Denver:
“The Origin of Titan—So Big … So Alone.” That was the playful title of a talk given here yesterday at the annual meeting of the Division for Planetary Sciences. The gist? Saturn’s relatively huge moon Titan, which orbits unaccompanied by the usual retinue of similar-sized moons, started out as three or four standard-issue satellites of the ringed planet that ran amok, collided, and merged into one huge moon and a few scraps of debris.
Douglas Hamilton got creative about Titan before the crowd because “the biggest mystery is how it came to be in the first place.” He didn’t see it happen except in a computer model. Might as well speculate, then: “Hamilton acknowledges he’s not sure how he would ‘prove’ that he is right.” Contrarily, though, Titan has few impact craters, showing it has a young surface, Science Daily said. Hamilton may want his new theory to motivate NASA to keep the funding flowing for the Cassini mission. It makes a nice story at least—kind of like the one that other planetary scientists say created Earth’s moon.
Whoops, about that moon theory: The theory of the origin of the moon by a collision has run into trouble. Daniel Clery wrote for a Science News focus, “Planetary scientists thought they had explained what made the moon, but ever-better computer models and rock analyses suggest reality was messier than anyone expected.” So the “Impact Theory Gets Whacked” itself, he titled his report from another scientific gathering.
Over the past decade, increasingly sophisticated computer simulations have shown that the tidy scenario clashes with what geochemists have discovered about moon rocks and meteorites from elsewhere in the solar system. As a result, researchers are casting around for new explanations. At a meeting at the Royal Society in London last month—the first devoted to moon formation in 15 years—experts reviewed the evidence. They ended the meeting in an even deeper impasse than before, as several proposed solutions to the moon puzzle were found wanting.
Bring in a bigger impactor: Because of the lunatic problems, some of the modelers are looking for an even wilder theory: the idea that Venus helped form the Earth’s moon. David Stevenson explained why: “It’s got people thinking about the direction we need to go to find a story that makes sense,” where story is the operative word.
Daniel Clery spends some time reviewing all the theories since Apollo that have ended up on the trash heap, the impact theory being the latest. “The giant impact has major problems,” Stevenson told his colleagues. “It doesn’t produce the moon as seen.” So much for all those simple-looking animations on TV. None of the latest ideas are simple. Jay Melosh remarked, “The solutions are contrived; they’re not natural.”
Also falling onto the trash heap is the notion that isotope ratios vary with radius across the solar system. Tossing that assumption opens up new plots for storytelling:
That explains why at the London meeting, when the session chairs jokily asked each speaker what single measurement they would most like to perform, many said they would like to examine a piece of rock from the planet Venus. Venus is Earth’s rogue twin, and together the two planets contain 80% of the mass between the asteroid belt and the sun. If it turns out that Venus has very similar isotope ratios to Earth, then it is much more likely that an impactor might have had them as well. “Venus is the key,” Stevenson said.
Since getting a piece of Venus from its hellish surface is highly challenging, this experiment won’t be done for some time. Space.com gave the “Wild new theory” good press anyway, giving the impression that the storytellers are “still on the trail of the detailed scenario” with their notion that “Back then, there were still a lot of things whizzing around.”
Not the Cambrian explosion, too: Astrobiology Magazine asks, “Did a Huge Impact Lead to the Cambrian Explosion?” Needless to say, even if a meteor hit the Earth way back when, it would say nothing about the origin of two dozen new animal body plans. Most likely, it would have destroyed life instead. It’s hard to know how anyone could take seriously the statement, “The ensuing environmental re-organization would have then set the stage for the emergence of complex life.” What if they set a stage, and nobody showed up? A stage setting is necessary, but not sufficient, to hold an intelligently-designed play. The notion sounds like an act of desperation to counter the argument for intelligent design that Stephen Meyer presented in his new book, Darwin’s Doubt. At least NASA got this right: “Animal life on Earth suddenly blossomed, with all of the major groups of animals alive today making their first appearance.” Almost sounds like Genesis.
See also the 9/23/13 entry, “Comet, Asteroid Impacts As the Answer to Everything.”
As we have repeated often before, when one’s theory reduces to random actions for no particular reason, one has abandoned science. If all one can say is “Stuff happens,” one has not explained anything. The story is no better than one made up by a fiction writer or cartoonist. What we observe is a smooth, well-differentiated Titan with a young atmosphere, and a moon around our Earth that supports life. Those are the facts. The most elegant explanation to be preferred, therefore, is one based on our common experience with ordered systems: that they were designed. That should be seen as superior to invoking a “wild new theory” that depends on “a lot of things whizzing around” that somehow did a bang-up job of creating an orderly solar system, just because stuff happens, even though the stories are “contrived” and “not natural.” Now who’s promoting pseudoscience? Look how long the Mars-sized impact theory for the origin of the moon was bandied about in the media as the scientific explanation for the moon, and now they tell us it has “major problems.” We don’t want scientists “jokily” asking each other what wild idea is next. We want them to face reality: the Earth and its moon appear designed for life. If they want to tell jokes, let them go into stand-up comedy instead.