February 6, 2006 | David F. Coppedge

Keeping Saturn’s Moons Old

The Saturn system has a problem: young moons.  The current consensus on the age of the solar system (4.5 billion years) cannot handle such young objects.  Richard A. Kerr in Science last month described the vexing problem:1

Why is there geology on Saturn’s icy satellites?  Where did these smallish moons get the energy to refresh their impact-battered surfaces with smoothed plains, ridges, and fissures?  These questions have nagged at scientists since the Voyager flybys in the early 1980s, and the Cassini spacecraft’s recent discovery that Saturn’s Enceladus is spouting like an icy geyser has only compounded the problem.   (Emphasis added in all quotes.)

The power to run those geysers is 8 gigawatts.  Cassini just released another distant image of Enceladus showing a distinct boundary between two terrains (see Cassini website), and captioned it “Youthful Enceladus.”  (For background information, see the 11/28/2005 entry about Enceladus eruptions, and for entries about its youthful surface, see 08/30/2005, 07/14/2005 and 03/04/2005.  See 01/07/2005 about Iapetus).
    Kerr described attempts by scientists to keep the little moons warm enough to support active geology.  These were discussed at the American Geophysical Union meetings in December, and also at the Cassini team’s Project Science Group meetings at JPL in January.  In short, “Perhaps the moons formed early and grabbed just enough heat-generating radioactivity from the nascent solar system” – that is, provided the models are tweaked in certain ways.
    One of the secret potions in their new models is aluminum-26, a radioactive element that decays rapidly and produces heat.  If enough is added in the model for Enceladus, it melts the core, produces a liquid ocean and warms the moon – for awhile.  Add some tidal heating, get the core to melt toward the south, and voila–active geysers billions of years later.
    For Iapetus, with its bulging equator and thin ridge of 12-km-high mountains, the scientists added a rapid spindown due to tides to its recipe of aluminum-26.  If Iapetus was spinning each 17 hours but was slowed by Saturn to 79 days as at present, and if it had enough Al-26 to stay flexible, it might have raised the equatorial bulge and ridge.  But it couldn’t have been hot for long or those features would have relaxed into a spherical shape.
    These efforts attempt to explain how apparently youthful features could persist for billions of years, but not everyone is ready to believe the models.  Kerr quotes Francis Nimmo of UC Santa Cruz who suggested there is perhaps too much investigator interference: “At each stage [of the calculations], there are several knobs you can twiddle,” he said, “There are so many free parameters it’s hard to make a strong statement.”  The modelers are continuing to twiddle the knobs till something resembling the real Enceladus and Iapetus emerge.


1Richard A. Kerr, “Planetary Science: How Saturn’s Icy Moons Get a (Geologic) Life,” Science, 6 January 2006: Vol. 311. no. 5757, p. 29, DOI: 10.1126/science.311.5757.29.

If this model is correct, how did Enceladus’ neighboring twin Mimas avoid a similar fate?  Why did Iapetus and Enceladus steal all the Al-26 and leave none for Rhea and Dione?  If this were unique to Saturn, it might be a quirk, but the whole solar system is filled with anomalies that do not fit into cozy models.  Every solution breeds new problems.
    Let’s use this story for a lesson about how science is done.  Practicing scientists assume that natural explanations (those that invoke only secondary causes) are better than those that invoke primary causes (such as creation).  To deny this is to be a heretic these days.  Even if one believes in God or some other philosophical design principle at the beginning of things, one cannot be a scientist without limiting one’s explanatory resources to secondary causes.  These are the rules, people like Eugenie Scott say, and many scientists and theologians assume this without thinking about it any deeper than retorting that invoking miracles is taboo in science (the either-or fallacy).
    This principle is known as methodological naturalism.  One is free to believe in God, but forbidden from invoking Him (or Her, or It) in scientific explanations.  What one does on a Sabbath or Sunday is a personal matter, but in the science lab, just act as if the God you believe in is limited to working through secondary causes.  At the risk of sounding completely nuts to this scientific culture, let us ask a few questions no one else seems to be asking.  Is this not Deism – a religion?  Practically speaking, what is there left for a God to do?  This type of methodology puts a Designer out of business and makes his existence irrelevant.  This is not science; it is religion or philosophy masquerading as science.
    Now, we are not going to suggest that natural causes have not been active on Enceladus or Iapetus for unknown amounts of time, and we are not wishing to insert some miracles to make Enceladus erupt or Iapetus magically form mountains at its equator.  We are not suggesting that the intervention of God is required continually or that He cannot work through natural law if He chooses to do so, which may be the overwhelming majority of the time.  Nor are we arguing that models are not useful in many contexts.  This discussion is not really about God at all, but about the truth claims of methodological naturalism in dealing with the unobservable past.  Even if one finds the right settings of the knobs that produce a resemblance to these bodies, how would one know the model is true?  By tweaking parameters in a model, which is not reality but a simplification of it, the modeler has only applied his or her intelligent design to achieve a correspondence between an imaginary prehistory and the actual history of the world.  Is the correspondence real or contrived?  If it feels satisfying to discover a correspondence, how is this feeling validated?  When a whole class of causes (specifically, intelligent causes) has been ruled out from the get-go, then what remains must be forced to fit even when it does not fit very well.
    Furthermore, numerous assumptions in the models are never addressed.  One is the age assumption.  A straightforward interpretation from unbiased observation is that these moons cannot be very old.  Yet the entire exercise is focused on preserving a fixed parameter – 4.5 billion years.  Why is this parameter never questioned?  Other astronomers are now claiming that planets can – and indeed must – form quickly, or else they risk being swept up into their parent stars (05/07/2001, 05/30/2002)  Some have even suggested gas giants could form in just a few hundreds or thousands of years (11/20/2002, 12/02/2002).  What is so sacred about this number 4.5 billion years that everything under the sun must be forced into it, no matter how improbable?  Could it be simply that Darwin needs the time?  And if these moons and the entire solar system actually were created by primary causation, how would they know?  Their very methodology precludes such a fact from being discovered, if that indeed is what happened.
    A commitment to unbounded methodological naturalism is a commitment to secondary causation into the past ad infinitum.  As such, it is indistinguishable from philosophical naturalism.  One cannot defend such a position scientifically, because it is an a priori assumption.  It sets arbitrary bounds on scientific explanations that may be very useful for observable, repeatable phenomena, but not necessarily for historical phenomena.  In operational science, a persistent search for secondary causation has been productive.  To assume it is, and must be, in every case, including origins, is not a scientific question, but a question of philosophy about science.
    When methodological naturalism produces the kind of refined storytelling as seen here, it seems more a quest to preserve one’s philosophical preferences than to know what actually happened.  It is not qualitatively different from choosing a philosophy or religion or hobby because it feels good.  In this game, a personal Creator actually involved in the creation and free to act in direct ways has been ruled out of bounds by dogma.  The creation myth is already decided even before the observations are allowed to speak.  Playing by these rules is bound to produce implausible scenarios in which multiple tweaks must be added in the right sequence to keep the story going.  Nature, however, often refuses to submit to our presuppositions.  Perhaps a little humility is in order.

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