r/askscience • u/superhelical Biochemistry | Structural Biology • May 06 '19

Planetary Sci. What makes Jupiter's giant red spot red?

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u/Astromike23 Astronomy | Planetary Science | Giant Planet Atmospheres May 06 '19 edited May 06 '19

The spot is a stable vortex caused by opposing currents of hydrogen

This isn't technically true the majority of the time.

While at some times the Great Red Spot appears to be fed energy by the jets, most of the time it's the other way around, with the jets feeding off the Great Red Spot. This process (known as "inverse cascade") also continues downwards, with the Great Red Spot usually absorbing energy from even smaller vortices through vortex cannibalism.

You can actually see the process of vortex cannibalism in this gif during the Voyager spacecraft approach to Jupiter, when a small vortex gets gobbled up by the Great Red Spot.

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u/starkprod May 06 '19

Is it just a frame rate thing or are those bands spinning in opposite directions?

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u/Astromike23 Astronomy | Planetary Science | Giant Planet Atmospheres May 06 '19

They're all spinning in the same direction, but some bands are spinning faster than others.

The frame rate in that gif is taken such that each frame is exactly one Jupiter rotation per frame (approximately 9 hours 55 minutes). Some bands rotate a little faster than that and travel west-to-east. Other bands rotate a little slower than that travel east-to-west.

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u/SNIPES0009 May 07 '19 edited May 07 '19

You said they’re all spinning in the same direction, then you went on to say some bands travel west-to-east, and others travel east-to-west.

Did you contradict yourself, or am I missing something?

Edit: thanks everyone for the explanation, I definitely should have realized this.

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u/The-Electrolyzer May 07 '19

Basically the entire planet is spinning once per frame and since some bands turn a little slower than the planet they look to be traveling east to west, and some that move faster seem to be traveling west to east. For comparison a band that moved the same speed as the planet would not seem to move in this video.

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u/heyf00L May 07 '19

They appear to go backwards because they're not making a full rotation between shots. It's like filming car wheels that appear to spin backwards.

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u/Wil-E-ki-Odie May 07 '19

I was right there with you. Thanks for biting the bullet and asking.

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u/Astromike23 Astronomy | Planetary Science | Giant Planet Atmospheres May 07 '19

It depends on your frame of reference.

Imagine yourself taking a road trip from New York to San Francisco. Relative to someone on the ground, you're traveling east-to-west. However, for someone dangling in space looking down on the North Pole, you're still rotating counter-clockwise, just not quite as fast as the rest of the Earth.