Despite ‘Magma Ocean’ Discovery, Io’s Volcanic Heat Remains a Mystery (Rumour Has It)

Now for some ‘news’, or rather “Daily (pseudo)Science Updates”.

Apparently, adding to the hefty list of evidence against both evolution and the universe having existed for a long time in general, Io gives out too much energy to be “old” (he must be flattered).

A recent creation astronomy video summarized the issue by stating, “If Io is young, it could still be cooling off from its initial formation. But if it’s really billions of years old, that energy would have dissipated long ago.” [What You Aren’t Being Told about Astronomy, Volume 1: Our Created Solar System. 2009. DVD. Directed by Spike Psarris. Creation Astronomy Media.]

Said video isn’t all that recent, mind – as you can see, it came out in ’09. What is, however, is a new study that shows that, as expected, there is a magma ocean beneath the surface of Io that is the source of the raw materials for its eruptions. The article about the study that they link to, however (I can’t see the study itself), has got nothing to say about any troubles when it comes to explaining Ioian heat loss. So where do they get the idea that Io is emitting an “order of magnitude” more radiation than it “should be” if the “long age” models were correct.

The answer to that question is here:

A review paper on the Io heat problem referenced German planet scientist Tilman Spohn, who “acknowledges that there is a gap of about one order of magnitude between the observed heat flow from infrared measurements and the heat flow theoretically determined from tidal [friction] dissipation models.”5 Io’s heat output is therefore around ten timesgreater than the long-age models say it should be.

Well, sort of. You see, the citation that the number ‘5’ refers to is  not anything by Spohn that either confirms or denies this, but a paper from the “Fifth International Conference on Creationism”. After some digging I’ve found that paper here. As there doesn’t seem to be anything new in the article, Let’s take a look…

The paper begins with an explanation of the Orbital mechanics involved. Io, Europa and Ganymede are in an approximate 1:2:4 orbital resonance. That is to say that for every one orbit of Ganymede around Jupiter, Europa goes around twice and Io four times. Also, this resonance apparently causes Io to have a much greater eccentricity than it would otherwise, and also prevents Io from drifting away from Jupiter. So far, this seems legitimate and is largely a paraphrase of one of the papers references (pdf). There is also a reference to the use of Lunar Recession as a creationist argument, but this isn’t the core premise of the paper.

The paper then goes on to talk about tidal heating and Io’s heat output. It first mentions the (accurate) prediction in 1979 (in the above referenced paper) that Io could be “the most intensely heated terrestrial-type body in the solar system ” due to tidal heating. They go on to say:

Though this was an excellent bit of work and the prediction was confirmed by Voyager and other observations, the heat produced by Io and radiated from its surface appears to be greater than the amount of heat generated by tidal dissipation. Of the energy transferred from Jupiter to Io via the tides, some of this energy produces internal heat in Io’s interior and some of it affects the orbit, tending to cause Io to slowly drift outward from Jupiter over time. The orbit resonance with Europa and Ganymede on the other hand tends to prevent Io from drifting away from Jupiter, though it increases Io’s orbital eccentricity and causes certain variations in Io’s orbit. Planetary scientists today generally believe that the tidal dissipation mechanism is an adequate source of heat to drive Io’s volcanism and explain Io’s high surface temperatures.

There are no citations here, so we’re going to have to suspend our disbelief and take the authors word for it that they’re going to back it up eventually. To continue:

Io radiates a great deal of energy; the total heat power given off over its whole surface would be approximately 10^14 Watts

This is backed up by a reference (pdf) which seems all in order. I’ve taken the liberty of using this figure to calculate the total energy output of Io over the last four billion years, assuming that the energy output has remained the same for the entire period (which is unlikely). The answer? 10^31 Joules. According to Wolfram|Alpha, 10^31 Joules is equivalent to:

It’s a lot, but not unbelievably high (for 4 billion years). Also, 10^14 Watts for only the one year comes out as 3.154×10^21 Joules, which is:

Again, not actually that much… An order of magnitude or two more than it receives from the sun, I’ll believe (the area Io exposes to the sun – pi times the square of it’s radius – is 0.08184 of that of the Earth, and Io is a lot further from the sun). To continue on that vein, 10^14 Watts over a mere 24 hours comes in at 8.64×10^18 Joules. The radiation gained by the Earth from the sun in the same period mentioned above appears to be around 1.5×10^22 Joules. Io, therefore, presents .05% of the area to the sun and gets 4% of the radiation for a given area, for  about .002% of the energy as a total. That comes out as 3×10^17 Joules of energy from the sun per day (ignoring Jupiter’s shadow etc), or about an order of magnitude or so less than the amount outputted by the Jovian Moon in a day. Whew… Anyway, where were we?

So this paper is trying to ‘explain’ the descrepancy between the energy output of Io and the amount of energy gained by Io from tidal forces. You will notice, however, that the author has not quantified or qualified the statement “the heat produced by Io and radiated from its surface appears to be greater than the amount of heat generated by tidal dissipation ”. It is also admitted that “Planetary scientists today generally believe that the tidal dissipation mechanism is an adequate source of heat to drive Io’s volcanism and explain Io’s high surface temperatures.”. Therefore, the paper needs to show that there is indeed a discrepancy here, and that the only explanation for this is that Io is exceedingly young – in the order of a few tens of thousands of years.

I’ll skip over the section on the moon’s geology and interaction with Jupiter and go straight to the section entitled “Tidal dissipation and the heat problem ”.

“Tidal dissipation”, you might have gathered by now, is the process by which an object (here Io) gains energy (as heat) from friction in its interior due to Io changing shape because of the differences in gravitational attraction from Jupiter between apojove (furtherest from Jupiter during orbit) and perijove (closest). As you might remember, Io’s orbit is somewhat more eccentric (non-circular) than it could have been due to the aforementioned orbital resonance. Now, as you would expect, energy gained by Io has to come from somewhere, and with regards to Tidal Dissipation it comes from Jupiter. We also have some information about the quality factor, which is:

This information can be used to analyse the models that the paper covers, but isn’t really useful.

Now, here we go:

Can the observations of the heat radiating from Io as well as the orbital observations be explained in a  framework that assumes Io is less than 10,000 years in age? Is tidal dissipation the most significant heat  source in Io?

Interesting that he doesn’t ask if the situation is explainable in a situation where Io is much older. But anyway…

In order to address these questions we must first look at the observational evidence on
how much heat is radiated from Io

What follows is a much more detailed dicussion on how the energy output of Io has been determined, concluding that the average over a 10 year study was 10^14 Watts, as above, which he will use as the standard that “theoretical models of the tidal dissipation need to be tested against ”. Fair enough.

If tidal dissipation is the largest source of heat in Io, then do we have observational evidence of Io
moving farther from Jupiter? Most planetary scientists researching the Io tidal problem seem to assume  that Io’s orbit must slowly expand as a result of the tidal mechanism.

Ok, apparently Io needs to move away from Jupiter for Tidal Dissipation to work. Why? You tell me… I seem to have missed something. Let’s continue on until it becomes clear.

But from observations of Io, any  change in Io’s orbit seems to be too small to measure. This is shown by results published by Lieske [14,  pp 146-158]. This study examined a large amount of data, including 16,000 eclipse observations from  1652 to 1983. Their published value, for the rate of change of the mean motion of Io, is (-.74 ∀ .87) X  10–11 yr–1. They suggest that Io is slowly evolving out from Jupiter and out of resonance with time. But,  when the uncertainty is greater than the measured change how can this be the proper conclusion? I will  take the view that this result indicates Io’s orbit is stable and exhibits no secular change. If tidal  dissipation is the largest heat source it seems we should be able to measure some long-term change in  Io’s orbit. Lieske [14, p 146] comments to this effect: “The modern infra-red measurements of the energy  emitted by Io . . . if interpreted as being due to interactions of Io with Jupiter . . . large secular changes in  the mean motion of the satellite ought to be observable.”

So, we have a reference for this. I’ll go check it out…
It seems to be as reported. The ellipses in the quote are where Lieske’s original citations have been removed, if you’re wondering. What would be nice is that if the author feels he can arbitrarily decide on no change in Io’s orbit for his calculations, can he provide the results using Lieske’s number (-.74 above)? Just to check his working, as it were…

A number of planetary scientists have commented to the effect that the heat produced by tidal dissipation  is less than the amount radiated from Io’s surface from observations. Cassen, Peale, and Reynolds, in  1982 published [5, p 102] that the heat produced by tidal dissipation had an upper limit of 3.3 X 1013 Watts (W). Later in the same article the authors state, “However, the upper bound on Io’s dissipation . . .  is also exceeded by a factor of two. This is a serious discrepancy whose resolution requires further  study.” Pearl and Sinton further comment in a different article in the same volume [5, p 753]:

The observed high value of the heat flux can be obtained by adjusting the tidal energy
dissipation factor (Q) of Io, but the required dissipation is untenable if the current
eccentricity of Io’s orbit is an equilibrium value determined by a balance of the effects
of dissipation in Jupiter and Io . . . . As Cassen et. al. . . . point out, the satellites would
have been pushed farther from Jupiter in 4.6 X 109 yr than their present distances.
Hence the solution of one enigma, the old 10 to 20 :m discrepancies, has led to yet
another enigma: apparent incompatibility with the present orbital configuration. . . .
Complete elucidation of the heat source remains a significant outstanding problem
resulting from the discovery of active volcanism on Io.

Finally, the “citation needed” is not longer. So this is where he’s coming from…Trouble is, I can’t get my hands on said paper.

So maybe there is a problem. What we’re actually after, by the way, is Tilman Spohn’s ideas, which is what started this 2000+ word essay in the first place (see what I mean about it taking longer to analyse and debunk than to make up?). I’ll skip ahead to that part. You miss a discussion on whether if the tidal effect is enough to explain the entirety of Io’s heat loss, then would Europa and Ganymede have volcanoes too? along with some other models of the heat flow on Io, which the author believes to be inferior to Spohn’s for the most part.

The most recent study of the tidal dissipation problem for Io is published by Tilman Spohn in 1997 [19]. I  will refer to this model as the Turbulent Convection Model. Spohn acknowledges that there is a gap of  about one order of magnitude between the observed heat flow from infrared measurements and the heat  flow theoretically determined from tidal dissipation models. Spohn assumes first of all that Io’s core has  at least a molten outer layer and that there is a significant amount of melt in Io’s mantle. He assumes  that Io formed undifferentiated and that initially Io and the other Galilean moons were in orbits different  than today. The Galilean moons Io, Europa, and Ganymede then evolved into resonance by the  influence of gravity over about 2.5 billion years of their early existence. Following this (about 2 billion  years ago) these three satellites settled into the current resonant orbits. Thus in Spohn’s approach, the  orbital interactions of these moons, as well as the tidal-orbit mechanism, have been operating for about 2  billion years. Spohn assumes that the temperature of Io’s core was 2300 Kelvin at the time Io entered  the resonance [19, p 369]. He further assumes a radiogenic heating rate of 10^9 Watts. In Spohn’s  approach the orbital parameters of Io undergo a periodic variation with a period of 10^8 years [9, p 61].  Spohn relates thermal parameter variations to the orbital parameters in a manner different from other  researchers (he does not use the Q parameter). Spohn’s model is a disequilibrium model.

N.B. The author has defined a disequilibrium model as one that rejects “either or both of”

1) any long-term change in Io’s orbit is due to the  effects of the tides and
2) there are no thermal effects in Io more significant than those produced by the
tides.

As it happens, Spohn’s model (I can’t find his paper, unfortunately) involves a structure of Io similar to that which has been announced in the article that makes this “news”, hence his reference there.

Now, the paper quotes this from Spohn’s paper:

The time required to generate the lava is about 10^4 years accounting only for the
latent heat. The hot-spots in the mantle would thus use about 10% of the tidal
dissipation power and store the energy in magma for about 10^4 years. This energy
can then be released at an average rate of 10^14 W from the surface in about a
century after the lava has erupted.

So, problem solved, right? The author disagrees:

Some potential weaknesses of Spohn’s analysis are the following. In Spohn’s approach, the turbulent  convection would have taken place in Io’s interior for over two billion years. In this time, Io’s interior  properties would be likely to change due to the heat transferred to the surface and the amount of sulfur  and silicate compounds deposited on the surface. It seems doubtful that the interior properties could  support this type of convection for such a long time. Secondly, the time scale of the build up of the  mantle hot spots, (or magma chambers) from Spohn’s model is only 10,000 years, yet the time frame of  the orbital oscillations is on the order of 100 million years. These two phenomena should be related in  some realistic way if tidal dissipation is the primary heat source in Io. Spohn also assumed a high  temperature value at the beginning of the resonance period in Io’s history (2300 K). This high  temperature would stem from radioactive decay in Io’s early history and a proposed period of greater  tidal dissipation in the past as Io’s orbit was evolving into resonance. Considering other studies of heat from radioactive decay, from an evolutionary viewpoint, this temperature may be unrealistic. Most other studies of Io’s interior use temperatures of approximately 1500 or 1600 K.

Sounds like “more research is needed” – that is, business as usual for science. The author, being a creationist, disagrees, it seems. He feels, in a classic “god of the gaps” way, that because the normal scientific way has failed, that means that Io must have been created relatively recently by God, with an initial heat source that is comparatively rapidly dissipating. In other words, the entire article can be summed up as: you can’t explain it right now, therefore God.

Interestingly, the authors model could potentially make predictions about the situation, not just conveniently explain it via divine intervention, the usual situation when it comes to creationism. If Io is losing energy at such a fast rate, could it be shrinking as it cools? What would that mean for the Galilean system? All this was 8 years ago, so what’s the situation now?
(and for that matter, how badly is this post written?)

To conclude with the paper, while it does successfully demonstrate that there is a problem, dismisses Spohn’s model too easily, and prematurely jumps to the conclusion that Io must have been created. But this is what you’d expect, considering….

As for the ICR article, what’s new? Nothing much. It’s just another Daily (pseudo)Science update.