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Starts With A Bang

Jupiter’s Great Red Spot got its first-ever close up last week

Nothing has ever come closer than NASA’s Voyager 1, nearly 40 years ago. Last week, all that changed.

“Juno will peer hundreds of miles downward into the atmosphere with its microwave radiometer, which passively senses heat coming from within the planet. This capability will enable Juno to reveal the deep structure of the Great Red Spot, along with other prominent Jovian features, such as the colorful cloud bands.” –Tricia Talbert

Jupiter is the Solar System’s largest planet, with the largest continuously-raging storm ever known.

At 317 the mass of Earth, Jupiter is the largest and most massive planet in the solar system, and it also boasts the largest storm: the Great Red Spot, as seen here. Image credit: NASA, ESA, and E. Karkoschka (U. Arizona).

Jupiter’s Great Red Spot (GRS) was discovered in 1665, raging continuously from at least 1830 until today.

At earlier times than the late 1970s, Jupiter’s Great Red Spot was in between the large, dark bands, rather than adjacent to one close to the equator. This may explain why the red spot has been shrinking in recent years. Image credit: NASA / Pioneer 10.

The spot appeared solid and larger in the early 20th century, but appeared smaller and more storm-like when Voyager 1 flew past in 1979.

A false-color image of the Great Red Spot of Jupiter from Voyager 1. The white oval storm directly below the Great Red Spot, a temporary storm that has since dissipated, has approximately the same diameter as the Earth. Image credit: NASA, Caltech / JPL.

At its maximum, the GRS was 40,000 kilometers across: more than three Earth diameters long.

Jupiter may be approximately 11–12 times the diameter of Earth, but the Great Red Spot has shrunk from a maximum of 40,000 km to merely 24,000 km across, as of 2017. Image credit: NASA; Brian0918 at English Wikipedia.

It’s barely half that extent today; if the shrinking continues, it will be completely circular by 2040.

Images from the Hubble Space Telescope show the Great Red Spot shrinking in extent and changing in shape even from 1995 (top) to 2009 (middle) to 2014 (bottom). Image credit: NASA, ESA, and A. Simon (Goddard Space Flight Center).

There are three theories as to why it’s red:

  • an organic compound,
  • red phosphorous,
  • or a reddish sulphur compound: ammonium hydrosulfide.
The first color movie of Jupiter from NASA’s Cassini spacecraft shows what it would look like to peel the entire globe of Jupiter, stretch it out on a wall into the form of a rectangular map, and watch its atmosphere evolve with time. Image credit: NASA/JPL/University of Arizona.

Juno, celebrating its one-year anniversary orbiting Jupiter, is equipped with cloud-penetrating instruments to find out.

Simulated images from the Juno mission, just in advance of orbital insertion last year. Image credit: NASA / JPL-Caltech, from their movie, Jupiter: Into the Unknown.

The GRS is colder and higher in altitude (by about 8 kilometers) than the rest of Jupiter’s atmosphere.

In theory, the differing properties of Jupiter’s great red spot, distinct from the rest of the atmosphere, could be related to thermal differences coming from below. Image credit: Art by Karen Teramura, UH IfA with James O’Donoghue and Luke Moore.

In theory, chemical and atmospheric processes occurring below the cloud-tops powers this storm.

With 600+ km/hr winds, this storm is much faster than any winds ever known on Earth.

Zooming in on the Great Red Spot at blue (left) and red (right) wavelengths reveals a unique filamentary feature that had never been seen before. There is still much to learn about this spot. Image credit: NASA/ESA/Goddard/UCBerkeley/JPL-Caltech/STScI.

Juno observed the Great Red Spot last week, 9,000 kilometers up, with all 8 instruments and its JunoCam imager.

Juno’s mission details are highlighted by eight independent instruments all capable of analyzing its atmospheric properties in a variety of ways, along with its high-resolution imager, Junocam. Image credit: NASA/JPL-Caltech.

Contingent upon new data, many mysteries might finally be solved.

Mostly Mute Monday tells the astronomical story of an astronomical object, phenomenon or mission in images, visuals, video and no more than 200 words.

Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.


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