Why are we seeing young phenomena in the planets if they are billions of years old? Some scientists are abandoning uniformitarian assumptions and admitting we are lucky to be witnessing them in “rare moments of glory.”
In Nature this week, Maggie McKee interviewed scientists who are struggling with short-lived phenomena in the solar system. The subtitle of her article, “Caught in the Act,” states, “We may be seeing some of the Solar System’s most striking objects during rare moments of glory.” Her first two paragraphs elaborate why this is unsettling for some:
Ever since Copernicus evicted Earth from its privileged spot at the centre of the Solar System, researchers have embraced the idea that there is nothing special about our time and place in the Universe. What observers see now, they presume, has been going on for billions of years — and will continue for eons to come.
But observations of the distant reaches of the Solar System made in the past few years are challenging that concept. The most active bodies out there — Jupiter’s moon Io and Saturn’s moons Enceladus and Titan — may be putting on limited-run shows that humans are lucky to witness. Saturn’s brilliant rings, too, might have appeared relatively recently, and could grow dingy over time. Some such proposals make planetary researchers uncomfortable, because it is statistically unlikely that humans would catch any one object engaged in unusual activity — let alone several.
It seems a bitter pill for some planetary scientists to “go against the grain of one of geology’s founding principles: uniformitarianism, which states that planets are shaped by gradual, ongoing processes,” she wrote. Then she quoted Jeff More (NASA-Ames) who explained that “Geologists like things to be the same as they ever were” because it’s “philosophically comforting because you don’t have to assume you’re living in special times.” Why that should be “comforting” was not explained.
McKee zoomed into each of these phenomena for more detail about what makes them look young:
- Saturn’s rings: The rings are 90% water ice but should be dirtier if they were old; “some planetary scientists say that the rings’ resplendence is hard to reconcile with a lifetime lasting billions of years.” That’s why hypotheses of a recent encounter with an icy interloper that broke apart and became the rings within the last few million years (just 10% of Saturn’s assumed age) have been put forth. An ad hoc solution like that, though raises other problems: all such candidate objects should have vanished 700 million years after the birth of the solar system, according to current theory. Close flybys by Cassini in years to come may confirm whether billions of years of dirt is hiding in the B ring, McKee said, but one responded, “if the Cassini results point to a low mass for the rings, it will be a real mystery.” This explanation, however, fails to explain why the thinner D, C, A, F, G, and E rings are so bright.
- Enceladus: The geysers of Enceladus are another thing that can’t be old; “researchers have struggled to explain how it can sustain such activity” on the order of 16 gigawatts – 10 times the amount they can account for by internal radioactive heating. “Several explanations have been put forward to account for this furious release of heat, but all rely on arguments that researchers are viewing the moon at a special time,” McKee said. It’s difficult to keep the geysers going for 10 million years (1/450th the assumed age of the moon), let alone 4.5 billion. One researcher who proposed a recent cracking from growing stresses in the crust has apparently been getting hard questions: “‘It seems like special pleading — we just happened to catch it in the act,’ says [Craig] O’Neill [Macquarie University, Sydney], echoing criticisms that he has heard when presenting the model at conferences.” Nearby Mimas “should be producing more heat than Enceladus and it doesn’t, and we don’t really understand why,” O’Neill said.
- Io: If Enceladus is a firefly, Io is a furnace, McKee wrote. It gives off 90,000 gigawatts through its incessant volcanoes, “several times more than would be expected from the simplest models of tidal interactions between the moon and Jupiter.” Again, it’s not that planetary scientists are unable to imagine scenarios in which we might be seeing Io at a special time; perhaps the moon’s orbital dance with the other moons makes it undergo periodic exaggerations of its eccentricity. Even though this “would satisfy the data,” one planetologist said, when thinking about the peculiarities of Io and Enceladus, “it’s possible we simply don’t understand them.”
- Titan: The largest moon of Saturn presents problems with both its atmosphere and surface. Atmospheric theories are up in the air, because “the atmospheric methane — and its effects on the landscape — ought to be short-lived” in the range of a few tens of millions of years. If sources of replenishment cannot be found (there are some disputed candidates thought to be ice volcanoes), it should have been long gone. Jeff Moore “thinks that researchers are seeing Titan at a unique and geologically fleeting time.” The question then becomes, why now, and what happened? In Moore’s hypothesis, the sun warmed up to a tipping point a few tens or hundreds of millions of years ago, levitating the frozen nitrogen and methane into an atmosphere that “rained like hell” onto the surface, creating the erosional features seen today. Ralph Lorenz [Johns Hopkins U] criticizes Moore’s view as “too simplistic” and pointed to “some evidence” (not mentioned in the article) that it would have taken billions of years to form Titan’s hydrocarbon-rich sand dunes.
McKee ended with a quote from Lorenz: “I think we have to have a much more nuanced view of Titan through time. Titan is bloody complicated.”
It’s not complicated at all, if you subtract out the needless billions of years. This article is important, in that in the 8 years of the ongoing Cassini mission to Cassini, and the 9 years since the end of the Galileo mission to Jupiter, scientists still have no answers to these age conundrums. Their uniformitarian philosophy makes them uncomfortable with the facts their own eyes are beholding. We should not be living in special times, but we appear to. (Understand that the Copernican principle does not mean that we are not special; see The Privileged Planet for corrective information.)
Here’s a classic case of ad hoc explanation to force observations into a web of belief. (This is called ‘special pleading’ in logic.) If science were about honestly following the evidence where it leads, these scientists would have to conclude that the solar system is much younger than thought. But they won’t do it, because they know Charlie D. (their idol) needs billions of years for life to evolve on Earth. Failing to provide those annual sacrifices to the idol would get them excommunicated from the Church of Darwin.
If Saturn’s rings, Enceladus, Io and Titan were the only problem worlds, they might have hope to rescue their beliefs someday. Unfortunately, the problems mount for uniformitarianism when one considers Mercury, Venus, Earth, the Moon, Mars, Jupiter and its moons, Uranus and its moons and rings, Neptune and its moons and rings, Pluto and the trans-Neptunian objects, comets, asteroids, dust – the whole system. There is hardly any planet or moon that met their uniformitarian expectations. We call on them: please, dump the assumption of billions of years, and all these things will start making sense. We do this out of sympathy for their discomfort, wishing them to sleep well for once.