April 23, 2024 | David F. Coppedge

Jupiter’s Volcanic Moon Defies Deep Time

New photos of Io are in from Juno,
prompting discussions about time.


The Juno mission has released stunning new images of Io, Jupiter’s second Galilean satellite. Look at the picture of a lava lake called Loki Patera that is as smooth as glass. That’s very unusual. Mission scientist Scott Bolton remarked,

There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake rimmed with hot lava. The specular reflection our instruments recorded of the lake suggests parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth.

This lava lake on Io is 127 miles wide. Artist’s concept of Loki Patera made using data from the JunoCam imager aboard NASA’s Juno spacecraft. With multiple islands in its interior, Loki is a depression filled with magma and rimmed with molten lava. Credit: NASA/JPL-Caltech/SwRI/MSSS.

Deep Time Challenges

To believe that Io has been erupting ultramafic (very hot) lavas for billions of years requires accepting two unlikely premises: that the volcanic moon receives enough heat from its neighbors through tidal pressure to keep its volcanoes going, and that a moon can cannibalize and regurgitate its entire mass hundreds of times.

NASA’s Juno Gives Aerial Views of Mountain, Lava Lake on Io (NASA Juno press release, 18 April 2024). Using divination on sulfur isotopes, a moyboy team at Caltech gives the reader a choice:

Although they can’t say exactly how long it has been volcanically active, it appears to have been erupting for between 2.5 and 4 billion years.

Either value is ridiculously long. It’s like asking if you believe your dog has eaten its barf and re-vomited it 100 times or 200 times. Maybe other options should be considered.

Violent volcanoes have wracked Jupiter’s moon Io for billions of years (Nature News, 18 April 2024). Readers are invited to believe unquestionably the first sentence:

Jupiter’s moon Io has been continuously shaped by volcanic activity for billions of years — possibly even for the Solar System’s entire 4.57-billion-year history, a study suggests.

Nice of them to “suggest” this.

Jupiter’s moon Io has been a volcanic inferno for billions of years (New Scientist, 18 April 2024). Reporter Alex Wilkins cuts to the chase. The implication of billions of years of volcanism is the following:

If Io has been consistently volcanic for billions of years, then this also means it will have recycled its deeper geological layers many times over, says Lionel Wilson at Lancaster University in the UK.

Instead of considering that something is drastically wrong with this implication, they just believe. But what happens to oatmeal left boiling on the stove for too long?

The Study

Isotopic evidence of long-lived volcanism on Io (Katherine De Kleer et al., Science, 18 April 2024). This is the research paper on which the claims are based.

Widespread volcanic activity on Jupiter’s moon Io is powered by tidal heating of its interior, due to Io’s orbital resonance with the neighboring moons Europa and Ganymede. Models of the formation of Jupiter’s large moons show that Io, Europa, and Ganymede were probably captured into the resonance during their formation process. If so, Io and Europa have experienced strong tidal heating for the entire 4.57 Gyr history of the Solar System, implying that Io has been volcanically active (either continuously or cyclically) over the same period.

Here is the team’s hard pill to swallow. Brace yourself:

A distillation process, consisting of recycling between the interior and atmosphere combined with mass loss from a gravitationally stratified atmosphere, is consistent with additional constraints on the interactions between Io’s surface and interior. If Io has maintained its current resurfacing rate (0.1 to 1.0 cm yr−1) over the entire 4.57 Gyr history of the Solar System, and if that resurfacing predominantly occurs through volcanic deposition, then the volume of material required is 10 to 100 times Io’s total volume. It is likely that Io’s mantle participates in this cycle: Io’s magmas are thought to be mantle material melted by tides and advected to the surface via heat pipes. Some fraction of the mantle, including its volatile elements, must therefore have been recycled through the surface environment at least tens to hundreds of times.

None of the popular reports question this interpretation. The authors state that it is an interpretation, not an observable fact:

We interpret the measured sulfur isotopic fractionation as due to a distillation process, whereby the lighter isotope is preferentially lost from a sulfur reservoir that is being continuously recycled between Io’s interior and atmosphere. Atmospheric escape then distills the portion of Io’s planetary inventory of sulfur that is available for recycling and loss.

The interpretation requires an auxiliary assumption: that Io has a stratified atmosphere, and there has been extensive mass loss of some isotopes of sulfur to space from the uppermost layer. That, in turn, required more assumptions: “we assumed that loss occurs only above the exobase and that gravitational stratification of the atmosphere is in the steady state.” Based on those assumptions, they calculate that Io has lost 94% to 99% of its original sulfur inventory to space over 4.57 billion years of eruptions. Why is there any left at all?

The presumptive authority that science journalists grant to “researchers” is evident here. With any other implausible claim in any other field, reporters would be hammering the experts with questions. How do you know that? How can you believe that? Did you ever consider the possibility that something is wrong with your assumptions or calculations? Have you looked at other possible interpretations of the data? How ridiculous would your conclusions have to become before you think outside the box and maybe question the 4.57 billion year assumed age?

Io global view from Galileo mission (NASA). The spots are all volcanoes, not craters.

Anecdote: CEH was born when the Editor heard a presentation by Dr Dennis Matson, chief scientist of the Cassini mission. Matson worried about the heat problem at Io. Data and calculations at the time showed that tidal heating could only produce a tenth of the required heat to sustain the volcanoes (see reproduced entry below from 16 Aug 2000). Now in 2024, these researchers are simply assuming the tidal heating is sufficient. We would like to see a re-analysis of the heat budget at Io; why did Dr Matson leave it as a mystery? He wasn’t the only one, it turns out. Other scientists have written about the heat problem in subsequent years.

Jupiter’s Moon Io Too Hot To Handle   08/16/2000
Exclusive  Dr. Dennis Matson, a planetary scientist with the
Cassini Mission reported to a group of team members that measurements of the surface of Io by the Galileo spacecraft from its Nov 99 and Feb 00 flybys indicate that the tiny moon emits more heat than can be accounted for by current theories. Io’s extremely hot lavas, on the order of 2000o K, are much hotter than lavas from most Earth volcanoes, which measure around 1200o K. These indicate special kinds of molten rock are involved, not just molten sulfur as previously supposed, which are mere byproducts of the high-temperature eruptions. What’s more, hardly a spot on the surface of Io cools before being smothered by another hot eruption. The temperature vastly exceeds what can be accounted for by popular theories of tidal flexing. Matson left the anomalous temperatures a mystery.
Update 10/26/2000  JPL has published a press release on these findings. It says the surface emits 13.5 watts per square meter, five times as much as the ground in Yellowstone’s thermal basins.  For a tiny moon that should have cooled eons ago, this amount of heat output is remarkable.

It’s only a mystery if you believe Io is 4.6 billion years old. Io is not the only body in the solar system too active for its age; Saturn, Uranus, Neptune, Enceladus, Triton and Europa and comets all show more heat or activity than they should if the solar system is as old as the current reigning paradigm claims.

Io’s Volcanoes Spell Trouble for Long Age Estimates   09/27/2002
Alfred S. McEwen of the University of Arizona’s Lunar and Planetary Lab, writing in the Sept 27 issue of Science, reviews some of the surprises that the Galileo spacecraft found at Io, the innermost moon of Jupiter. Although its volcanism was well known since the Voyager flybys in 1979, scientists were shocked to measure lava temperatures higher than anything on earth (~1800 oK), suggesting Io has an iron and magnesium rich (ultramafic) crust. According to current theories of mantle differentiation, however, such denser elements should not be present at the crust in sufficient quantities to account for the observations. McEwen explains how, over billions of years, it should all be gone:

The idea that Io is an ultramafic world seems at odds with the well-understood process of magmatic differentiation. If Io has a solid lower mantle capped by a partially molten layer, as believed by most planetary geophysicists, then Io’s crust should be strongly depleted in elements like Mg. As mantle rocks begin to melt, the first component to melt has a lower density. It segregates and rises toward the surface after ~10% melting of a given volume of the solid mantle. If Io’s typical heat flow over geologic time is just 10% of today’s value, then we can expect 1012 km3 of silicate melt over the last 4000 million years–40 times the volume of Io. There should thus have been sufficient heat to melt 10% of Io’s volume 400 times. After just four episodes of such partial melting, Io should have formed a low-density crust ~50 km thick (11). High-temperature, dense mafic or ultramafic lavas could only rise through the thick low-density crust under extraordinary circumstances.

As a possible solution to this dilemma, he points to the model of Keszthelyi that Io’s mantle might be a crystal-rich magma ocean, for which there might be indirect support, but he admits “it is difficult to explain how Io first got into that state.” Maybe we are misinterpreting sparse data. He leaves the mystery unresolved.

A new series of dramatic pictures of Io from the Galileo spacecraft was released December 9, 2002.

Dr. Ed Stone, the Voyager project scientist, has admitted many times that the discovery of active volcanoes on Io was a total surprise. These small bodies, far from the sun, should long ago have become frozen and dead. Even the theory of tidal flexing does not appear anywhere near sufficient to account for the amount of activity observed. That was bad enough, but the high temperature of the lavas, indicating the presence of dense elements, was a further blow to conventional theories.

The only suggestion that makes sense is that Io is much younger than the assumed four billion year age of the solar system. When other solar system phenomena also defy long ages, like comets and rings and short-lived radionuclides, why must the age parameter be sacrosanct? Two reasons: a young solar system would defy naturalistic explanations by indicating abrupt appearance, and it would not allow time for evolution (begging the question that four billion years would be enough, anyway). Take note of the observational evidence. At even 10% the current heat output, McEwen states, Io would have had time to completely melt 40 times in 4 billion years. At current heat output rates, that would be 400 times. With anomalies that large, it’s time for some creative alternatives.

See also these subsequent CEH articles about problems with Io’s volcanoes:


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