New study traces Io’s volcanic tides

Posted: August 11, 2019 by oldbrew in Cycles, research, volcanos
Tags: , , ,

Credit: NASA [click on image to enlarge]

In a 2015 Talkshop post we found a resonant period of 486.5 days for the inner three of the four Galilean moons of Jupiter: Io, Europa and Ganymede. Here the researchers find a period of 480-484 days, which clearly looks very much the same as our period, linked to recurring volcanic activity. They find this ‘surprising’, but the repeating alignments of these moons with Jupiter – at the same time interval – look to be more than a coincidence.

Hundreds of volcanoes pockmark the surface of Io, the third largest of Jupiter’s 78 known moons, and the only body in our solar system other than Earth where widespread volcanism can be observed, says

The source of the moon’s inner heat is radically different than Earth’s, making the moon a unique system to investigate volcanism.

A new study in the AGU journal Geophysical Research Letters finds Io’s most powerful, persistent volcano, Loki Patera, brightens on a similar timescale to slight perturbations in Io’s orbit caused by Jupiter’s other moons, which repeat on an approximately 500-Earth-day cycle.

The new results are surprising because volcanoes on Io do not erupt in time with larger fluctuations in the far greater stresses inflicted on Io during the moon’s 1.77-Earth-day orbit around Jupiter. Internal friction from these stresses generates the heat that powers Io’s volcanoes, but fluctuating stresses during the short period of Io’s orbit don’t appear to squeeze magma to the surface.

The new study, which analyzed 271 nights of observations of Loki Patera from Hawaii’s Keck and Gemini North telescopes from 2013–2018, and more sporadic observations dating back to 1987, suggests the gentler, 500-day cycle may act on the right timescale to move magma and bring it to the surface of the moon in an eruption.

“The stresses on Io’s interior vary a lot during that 1.77-day orbit,” said Katherine de Kleer, a planetary scientist at the California Institute of Technology and the lead author of the new study. “As far as anyone has been able to tell, there is no variation in Io’s volcanoes on this 1.77-day scale, so it’s a bit counterintuitive that we would see a response over the longer period, when the changes in stress are lower.”

Understanding this dynamic may provide clues to Io’s mysterious interior as well as the interiors of other bodies in the solar system warmed by a fluctuating pull of gravity, an effect called tidal heating.

“We know almost nothing about what Io’s magma chambers and conduits are like, so Loki Patera’s behavior is giving us a small window into an area where we currently have zero information,” said de Kleer.

Moon dance

Io has a hot interior because its tight orbit around Jupiter is not circular. The moon is stuck in an eccentric orbit because it resonates with Jupiter’s largest moons, neighboring Europa and Ganymede, caught between their influence and the massive gravity of Jupiter.

Europa’s orbit around Jupiter is twice as long as Io’s, and Ganymede’s orbit is twice as long as Europa’s. This 1:2:4 rhythm means the pull of gravity from the other two moons repeats consistently as Io orbits around Jupiter.

Io’s distance from Jupiter changes over the course of its elliptical orbit, so it experiences a different amount of Jupiter’s gravity as it circles the massive planet. The shifting pull of Jupiter and the other moons stretches and compresses Io on its two-day orbit around Jupiter. This generates enough heat from friction within the materials of the moon’s interior to melt rock into magma.

Researchers studying the more than 400 volcanoes on Io have looked for evidence that they erupt on the same beat. Such a fluctuation with daily orbit occurs on Saturn’s moon Enceladus, which has an underground ocean that spurts out through cracks in the moon’s frozen surface. Water geysers on Enceladus bloom largest when the moon is at its furthest point from Saturn and the fractures sourcing the geysers are being pulled open.

But the new study did not find evidence that Loki Patera keeps the same time as Io’s two-day orbit around Jupiter. Instead, its brightness appears to fluctuate at a similar timescale to subtle perturbations in Io’s orbit.

Although orbital resonance with Europa and Ganymede exerts the largest tidal effects on Io, the neighboring moons also slightly warp the shape of Io’s orbit in cycles lasting 480-484 days and 461–464 days.

Diagram of orbits and synodic periods

Loki Patera appears to erupt on a cycle that is similar to this timeframe, according to the new study.

Full article here.
– – –
The recurring pattern shown in the Talkshop chart (right) takes about 486.5 days on average to complete one cycle, according to our model.

Source: Why Phi? – the resonance of Jupiter’s Galilean moons

275 Io = 486.513 days
137 Europa = 486.512 days
68 Ganymede = 486.510 days
[Orbit data from Wikipedia]

  1. oldbrew says:

    Research Letter: Variability in Io’s Volcanism on Timescales of Periodic Orbital Changes

    Plain Language Summary

    Tidal heating is one of the central processes that generates heat in the interiors of planets and moons and is in part responsible for the existence of subsurface oceans and geological activity on moons in the outer solar system. Under this process, the amount of heating that occurs, and the stresses in the crust, vary periodically with the periodic tidal flexing. As a result, we might expect that any geological activity powered by tidal heating, such as volcanic eruptions on Jupiter’s tidally heated moon Io, would also vary periodically. Indeed, the water geysers on Saturn’s moon Enceladus vary in strength over the course of Enceladus’ orbit around Saturn due to tides opening and closing fissures. Io takes only 1.77 days to orbit Jupiter, but its orbit is also slowly changing in time with a period of ~480 days. We compare the variability of Io’s volcanoes with the evolution of its orbit and find that the quasiperiodic behavior of Loki Patera, the most powerful volcano on Io, follows a similar pattern as the orbital changes. We explore whether this volcano could be brightening and fading in response to changes in the heating and stresses produced by tides in its interior and what implications this has for the geophysical processes in Io’s interior.

  2. oldbrew says:

    50:50 ratio of the Galilean moon masses — Io+Callisto to Europa+Ganymede.

    “it’s a bit counterintuitive that we would see a response over the longer period, when the changes in stress are lower.”

    This is the length of the repeating cycle of the three moons. The whole cycle repeats, not just the duration itself.

  3. JB says:

    Clues they have, understanding they have not. The latter does not come from the former, but through insight into processes, unconstrained by past interpretations. I’m not convinced tides are the source of heat, though they may be an element contributing.

  4. oldbrew says:

    In Io’s case there’s a direct link with Jupiter of enormous electrical power, said to be five million amperes.

    – – –
    Aurora Flare-ups on Jupiter Caused by Volcanic Moon Io

  5. Damian says:

    From wiki:
    “Io has an extremely thin atmosphere consisting mainly of sulfur dioxide (SO
    2), with minor constituents including sulfur monoxide (SO), sodium chloride (NaCl), and atomic sulfur and oxygen.[110] The atmosphere has significant variations in density and temperature with time of day, latitude, volcanic activity, and surface frost abundance.”

    Sulfur monoxide, sodium chloride and oxygen are all products if electrolysis. I don’t know about Sulfur dioxide and I don’t know what atomic Sulfur is or why my phone keeps capitalising Sulfur.

    Mercury has a similar atmosphere.

  6. Damian says:

    Io’s volcanos have all the characteristics of an arc discharge, according to the Electric Universe guys.

  7. Damian says:

    “We explore whether this volcano could be brightening and fading in response to changes in the heating and stresses produced by tides in its interior and what implications this has for the geophysical processes in Io’s interior.”

    It would be more interesting to see if the volcano’s changing characteristics correlate in any way with the auroral points?

  8. oldbrew says:

    USGS Volcano Hazards Program

    By far the most abundant volcanic gas is water vapor, which is harmless. However, significant amounts of carbon dioxide, sulfur dioxide, hydrogen sulfide and hydrogen halides can also be emitted from volcanoes.
    [bold added]
    – – –
    Volcanology of Io

    Observations of Io by passing spacecraft (the Voyagers, Galileo, Cassini, and New Horizons) and Earth-based astronomers have revealed more than 150 active volcanoes. Up to 400 such volcanoes are predicted to exist based on these observations.
    . . .
    As a result of the presence of significant quantities of sulfurous materials in Io’s crust and on its surface, some eruptions propel sulfur, sulfur dioxide gas, and pyroclastic material up to 500 kilometres (310 mi) into space, producing large, umbrella-shaped volcanic plumes.

  9. oldbrew says:

    ‘Europa’s orbit around Jupiter is twice as long as Io’s, and Ganymede’s orbit is twice as long as Europa’s. This 1:2:4 rhythm means the pull of gravity from the other two moons repeats consistently as Io orbits around Jupiter.’

    But to get the true picture we have to look at the synodic data, rather than the orbital data – as the Galilean Moons graphic in the post shows. The ‘pull of gravity’ is due to the alignments with Jupiter, not to the orbit numbers themselves.

  10. oldbrew says:

    Just came across this…

    Orbital Period Ratios and Fibonacci Numbers in Solar Planetary and Satellite Systems and in Exoplanetary Systems
    Vladimir Pletser
    (Submitted on 7 Mar 2018)

    It is shown that orbital period ratios of successive secondaries in the Solar planetary and giant satellite systems and in exoplanetary systems are preferentially closer to irreducible fractions formed with Fibonacci numbers between 1 and 8 than to other fractions, in a ratio of approximately 60% to 40%. Furthermore, if sets of minor planets are chosen with gradually smaller inclinations and eccentricities, the proximity to Fibonacci fractions of their period ratios with Jupiter or Mars′ period tends to increase. Finally, a simple model explains why the resonances with ratios of orbital periods P1 and P2 of successive secondaries being equal to ratio of small integers p and (p+q), P1/P2=p/(p+q), are stronger and more commonly observed.
    – – –

    NB some are linked to Lucas numbers instead but that’s a minor quibble. We have an example in the solar system: the Venus-Earth-Mars synodics have a 3:4:7 ratio.

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