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Jupiter’s Great Red Spot as Heat Source

Speculating about what an advanced extraterrestrial civilization might do has kept us occupied for the last two days, with gas giants like Jupiter the primary topic of conversation. We don’t know if it’s possible to ignite a gas giant to provide new sources of energy. But with Juno getting ready to measure Jupiter’s aurorae, we’re looking at naturally produced energy today, and now we have interesting work on the planet’s Great Red Spot that comes out of Earth-based observations. The enormous storm turns out to be a key factor in heating Jupiter’s atmosphere.

And what a storm it is. We knew about the Great Red Spot as early as the 17th Century because its span — three Earth diameters — qualifies this highly visible maelstrom as the largest hurricane we know of. Winds can take six days to complete one circuit of the Great Red Spot, which has varied in size and color ever since it was discovered. It is now observed to span 22,000 km by 12,000 km in longitude and latitude, respectively.

The Great Red Spot gives us a source of energy to heat Jupiter’s upper atmosphere but thus far we have lacked evidence of its effect upon temperatures. Now an analysis based upon new infrared data is changing our view of temperatures high above Jupiter’s visible disk.

Image: Acquiring Jovian spectra. Bright regions at the poles result from auroral emissions; the contrast at low- and midlatitudes has been enhanced for visibility. Great Red Spot (GRS) emissions at mid latitudes are indicated by the red arrow. Additional info: The vertical dark line in the middle of the image indicates the position of the spectrometer slit, which was aligned along the rotational axis of Jupiter. Image shown is taken from the slit (slit-jaw imaging) using the “L-filter” (3.13 – 3.53 μm). Credit: J. O’Donoghue, NASA Infrared Telescope Facility (IRTF).

The results come from James O’Donoghue (Boston University) and colleagues, who report their findings on the matter today in Nature, using 2012 data from the SpeX spectrometer on NASA’s Infrared Telescope Facility in Hawaii. The issue caught the astronomers’ attention because at mid- to low latitudes, temperatures in Jupiter’s upper atmosphere are hundreds of degrees warmer than heating from the Sun can explain. We’re looking at non-Solar energy whose sources could be studied by creating heat maps of the entire planet.

This is what the O’Donoghue set out to do, realizing that what his team refers to as an ‘energy crisis’ occurs not just on Jupiter but on other giant planets as well. One explanation for Jupiter has been auroral heating mechanisms that pump energy into the upper atmosphere. But the low to mid-latitudes lack this kind of heat source and yet remain 600 K warmer than can be explained by solar heating. The paper makes the case for a different kind of source:

A more likely energy source is acoustic waves that heat from below (also via viscous dissipation); this form of heating requires vertical propagation of disturbances in the low-altitude atmosphere. Acoustic waves are produced above thunderstorms, and the subsequent waves have been modelled to heat the Jovian upper atmosphere by 10K per day and on Earth have been observed to heat the thermosphere over the Andes mountains. On Jupiter, acoustic-wave heating has been modelled to potentially impart hundreds of degrees of heating to the upper atmosphere. However, to the best of our knowledge, no such coupling between the lower and upper atmosphere has been directly observed for the outer planets, so vertical coupling has not been seriously considered as a solution to the giant-planet energy crisis.

The team found that high altitude temperatures on Jupiter are greater than expected when the Great Red Spot is directly below. In fact, the atmosphere above this region is hundreds of degrees hotter than anywhere else on the planet. The temperature spike above the Great Red Spot points to coupling between lower and upper atmosphere. The authors believe the heating is caused by atmospheric turbulence that rises because of the shear between the storm and surrounding atmosphere, with propagating waves depositing their energies high above.

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Image: Turbulent atmospheric flows above the storm produce both gravity waves and acoustic waves. Gravity waves are much like how a guitar string moves when plucked, while acoustic waves are compressions of the air (sound waves). Heating in the upper atmosphere 800 kilometers above the storm is thought to be caused by a combination of these two wave types ‘crashing’ like ocean waves on a beach. Credit: Art by Karen Teramura, UH IfA, James O’Donoghue

Co-author Tom Stallard (University of Leicester) puts the work into the context of ongoing missions like Juno:

“This fantastic result, showing how the upper atmosphere is heated from below, was produced directly from Leicester’s 2012 observing campaign, which was designed to try and answer why Jupiter’s upper atmosphere is so hot. Juno will be measuring the aurora and its sources, and we expected the auroral energy to flow from the pole to the equator. Instead, we find the equator appears to be heated from plumes of energy coming from Jupiter’s vast equatorial storms.”

The paper is O’Donoghue et al., “Heating of Jupiter’s upper atmosphere above the Great Red Spot,” Nature, published online 27 July 2016 (abstract).

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Comments on this entry are closed.

  • Marshall Eubanks July 27, 2016, 14:20

    We know that material in the Great Red Spot (GRS) is not convected down into the Jovian depths, but sticks around at altitude, and so that it would be a good location for Jovian biology to flourish. (We also know that spots start out white, and turn red over a few years – is the red something like an algae bloom?) Now we find that the GRS (and maybe other spots) are warmed by the deep interior; even better conditions for a biological habitat. We need to send a balloon to the GRS to see if there is any life there.

    By the way, in gravity waves the restoring force is gravity. The waves crashing on the beach when you go to the ocean are gravity waves. In guitars, the restoring force is the string tension – Commander Hadfield in his “Space Oddity” video showed quite clearly that guitars work well in zero-g, and thus do not need gravity as a restoring force.

  • ljk July 27, 2016, 14:46

    For anyone who has a copy of the Time-Life Science Series book titled Planets (whose science advisor was some guy named Carl Sagan), first published in 1966, look for the artist’s depiction of the Great Red Spot – the one which shows the “spot” hovering over the main Jovian cloud deck. Now tell me that new artwork shown above in the main article here does not remind you of the one in Planets, even though they are about two different concepts.

    What’s old is new again. :^)

  • Marshall Eubanks July 27, 2016, 14:55

    Oh, and the top-side Jovian atmosphere cannot be heated by by “600 K.” I suspect that’s a typo for “60 K.”

    • Alex Tolley July 27, 2016, 19:13

      It says 600K in the Nature Letter.

      The low to mid-latitudes do not have such a heat source,
      and yet are measured to be near 800 K, which is 600 K warmer than
      can be accounted for by solar heating

    • Marshall Eubanks July 27, 2016, 19:18

      I was wrong about the temperature – this paper concerns “altitudes between 600 km and 1,000 km above the 1-bar pressure level.” With a scale height of 27 km, even 600 km is at a very low pressure – maybe 200 picobars (20 micropascals). At such low pressures, temperatures can indeed be quite high.

  • Geoffrey Hillend July 27, 2016, 16:27

    Acoustic waves and gravity waves crashing together to make heat. Those must be some high energy sound waves to get that effect. The wind shearing must be really strong so there is high energy compression sound waves. Interesting theory which I’d like to know a little more details on how gravity and sound waves can interact to produce heat.

    Hurricanes on Earth are transporters of heat. They take the heat from the lower atmosphere and transport through the eye of the storm and into the upper atmosphere.

  • Geoffrey Hillend July 27, 2016, 16:47

    Excuse me. After reading the abstract, I see gravity and acoustic waves are not crashing together but either these two types of waves are crashing with a lower density region of the upper atmosphere.

  • Horatio Trobinson July 31, 2016, 22:07

    Has anybody done the maths, what would be an optimal orbit for a space station right above the GRS that could keep it safe from Jupiter’s massive tidal forces and radiation, but at the same time close enough to be able to make use of this virtually unlimited energetic source?

    Is such a compromise even possible?

    I can imagine a space station on a relatively safe orbit, dropping an energy collector satellite (or set of satellites) right above the outermost layer of Jupiter’s atmosphere and precisely above the GRS, with this collector in turn transforming the energy it captures and beaming it up to the space station in the form of a laser beam.

    • Michael August 1, 2016, 9:45

      The amount of energy is large but of low quality, if we dangled a conductor towards Jupiter from Io then we can talk about energy, or even wrap conductors around the moons (poles) then we will have enormous amounts of energy!