Solving the Mystery of Jupiter’s Great Red Spot

Jun 4, 2016

By Adrienne LaFrance

The Great Red Spot wasn’t always red.

Early observers said the oval swirl, Jupiter’s most puzzling and distinctive marking, was more of a salmon pink—or even pale violet—before darkening to a brick red in the early 1880s. After that, it seemed on the brink of vanishing for a time, before it swelled and again deepened in hue. Today it is again shrinking, and it’s turning orange.

No one is sure why, but we may soon find out. NASA’s Juno mission is currently on the way to Jupiter, where it will take an unprecedented close-up of the Great Red Spot.

“We’re going to skim within 3,100 miles of Jupiter’s cloud tops—in between the cloud tops and just inside the most intense portion of the radiation belt,” said Rick Nybakken, Juno’s project manager. “Nobody’s ever ventured there before. No spacecraft has ever operated this close to Jupiter.”

People have been captivated by the planet’s spot for centuries. Scientists today know that the Great Red Spot is an anti-cyclonic storm, a hurricane-like high pressure system that’s three times the size of Earth and has been raging for 400 years—maybe longer. (Its nickname seems to date back only to the 1870s, however.) The chaotic storm has churned for so long, astronomers surmise, because it has never made landfall—there is, after all, no land to fall upon.

The fact that the spot is actually a storm swirling in the Jovian atmosphere helps explain one of the characteristics that astronomers a century ago found most troubling. The Great Red Spot didn’t exactly stay put; it seemed detached from the planet’s surface. “No observer understands the cause of this huge rift,” The New York Times reported in 1880. “It may be an opening in the cloud-atmosphere disclosing the more solid matter beneath, and it may be something beyond human ken.”

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One comment on “Solving the Mystery of Jupiter’s Great Red Spot”

  • @OP – Today it is again shrinking, and it’s turning orange.
    No one is sure why, but we may soon find out. NASA’s Juno mission is currently on the way to Jupiter, where it will take an unprecedented close-up of the Great Red Spot.

    Perhaps the Juno Probe can follow up on this discovery made by an Earth-based telescope!

    Jupiter’s Great Red Spot – a hurricane three times bigger than Earth – is blasting the planet’s upper atmosphere with heat, astronomers have found.

    Using measurements from an infrared telescope in Hawaii, a UK and US team found evidence for temperatures as high as 1,500C – hundreds of degrees warmer than anywhere else on the planet.

    They suggest the hotspot is created by thunderous soundwaves “breaking” in the thin upper reaches of the atmosphere.

    The research is published in Nature.

    It arguably solves what planetary scientists had dubbed an “energy crisis” for gas giants like Jupiter: temperatures in their upper atmospheres soar much higher than can be explained by solar energy – especially given their vast distances from the Sun.

    If the mysterious heat were generated by local sources, like Jupiter’s famous storm, then the conundrum would be solved – and these measurements are the first direct evidence of any such activity.

    Study co-author Dr Tom Stallard, from the University of Leicester, said this was a major step forward in a “20-30 year odyssey” to try and understand heat flow on Jupiter.

    “Ever since Voyager, we’ve had measurements of the temperature at the top of Jupiter’s atmosphere, and it’s been hot across the whole globe – from the poles, all the way to the equator,” he told the BBC.

    The freshly discovered spike in temperature, detected using a spectrometer at the Nasa Infrared Telescope Facility (IRTF) in Mauna Kea, Hawaii, offers a solution.

    Several hundred km directly above the clouds of the Great Red Spot, the hotspot suggests that high-altitude heat is somehow created by the turmoil beneath.

    “Several people have argued that it’s likely that the heat comes from below, but the observations have never backed them up,” Dr Stallard said.

    Ionic thermometer

    The key to revealing the temperature spike was a tiny ion: H3+, a hydrogen molecule (H2) with an added proton. It is incredibly reactive and consequently, short-lived and rare on Earth. But in the sparse fringe of Jupiter’s outer atmosphere there is almost nothing else for it to react with.

    Crucially, this ion works like a glowing, long-range thermometer for scientists, if they have the right sort of telescope – such as the spectrometer at the IRTF, which gathered the relevant data in a single nine-hour window back in 2012.

    “Just by measuring its light, you can find out the temperature wherever it is,” said Dr O’Donoghue. “And it’s throughout all of the gas giant upper atmospheres – so it’s essentially an in situ temperature probe.”

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