Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:
HOT SPOT
This is Jupiter.
And this is Jupiter in infrared.
In 1995, the Galileo spacecraft dropped a small probe into Jupiter’s atmosphere. It was supposed to sample the chemicals in Jupiter’s clouds, but in a case of extraordinary bad luck, the probe fell into an empty gap between cloudbanks and collected virtually no data.
I like to imagine the clouds separating before the probe, like Moses parting the Red Sea, but I’m sure that’s not how it actually happened.
These gaps in the Jovian clouds are called hot spots. The thin atmospheric gases in these regions are actually quite cold, but when viewed in infrared, they appear hot due to the intense heat of Jupiter’s interior shining through.
The hot spots form—they always form—about seven degrees north of the equator. Eight to ten of them will appear at a time, evenly spaced along that seven degrees north longitude line, wrapping all the way around the planet.
This has led scientists to conclude that Jupiter’s hot spots are caused by a standing wave (more technically, a Rossby wave) in Jupiter’s atmosphere. The peaks and troughs of the wave correspond to the thickening and thinning of the surface clouds.
The Juno spacecraft’s JIRAM instrument (Jovian InfraRed Auroral Mapper) is specifically designed to study Jupiter’s aurorae (as the name implies) and also the hot spots. By staring straight down into a hot spot with an infrared spectrometer, scientists hope to identify the chemical composition of the deeper atmospheric layers. Among other things, they believe they’ll find a layer of water clouds.
Of course the Great Red Spot is a weird and mysterious phenomenon too. It deserves the high level of scrutiny it gets. But of all the spots on Jupiter, the hot spots may turn out to be the most interesting and revealing of the planet’s features.
Links
Jupiter’s Atmosphere Has Weird Hot Flashes from Space.com.
“Hot Spots” Ride a Merry-Go-Round on Jupiter from NASA.gov.
Planet Pailly 
I’d imagine that the term “hot spot” is relative since Jupiter’s average temperature at the 1 bar level is -108 C (at least according to Wikipedia).
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I’m guessing the hot spots themselves are even colder than that due to the low atmospheric pressure. They just look hot in infrared because you can see through to the planet’s interior layers.
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