A Recourse to Pastry

There’s something wrong about the displays laid out on Al’s pastry counter — no symmetry.  One covered platter holds eight pinwheels in a ring about a central one, but the other platter’s central pinwheel has only a five-pinwheel ring around it.  I yell over to him.  “What’s with the pastries, Al?  You usually balance things up.”

“Ya noticed, hey, Sy?  It’s a tribute to the Juno spacecraft.  She went into orbit around Jupiter on the 5th of July 2016 so I’m celebrating her anniversary.”

“Well, that’s nice, but what do pinwheels have to do with the spacecraft?”

“Haven’t you seen the polar pictures she sent back?  Got a new poster behind the cash register.  Ain’t they gorgeous?”Jupiter both poles“They’re certainly eye-catching, but I thought Jupiter’s all baby-blue and salmon-colored.”

Astronomer Cathleen’s behind me in line.  “It is, Sy, but only in photographs using visible sunlight.  These are infrared images, right, Al?”

“Yeah, from … lemme look at the caption … Juno‘s JIRAM instrument.”

“Right, the infrared mapper.  It sees heat-generated light that comes from inside Jupiter.  It’s the same principle as using blackbody radiation to take a star’s temperature, but here we’re looking at a planet.  Jupiter’s way colder than a star so the wavelengths are longer, but on the other hand it’s close-up so we don’t have to reckon with relativistic wavelength stretching.  At any rate, infrared wavelengths are too long for our eyes to see but they penetrate clouds of particulate matter like interstellar dust or the frigid clouds of Jupiter.”

Jupiter south pole 1
NASA mosaic view of Jupiter’s south pole by visible light

“So this red hell isn’t what the poles actually look like?”

“No, Al,  the visible light colors are in the tops of clouds and they’re all blues and white.  These infrared images show us temperature variation within the clouds.  Come to think of it, that Hell’s frozen over — if I recall correctly, the temperature range in those clouds runs from about –10°C to –80°C.  In Fahrenheit that’d be from near zero to crazy cold.”

“Those aren’t just photographs in Al’s poster?”

“Oh, no, Sy, there’s a lot of computer processing in between Juno‘s wavelength numbers and what the public sees.  The first step is to recode all the infrared wavelengths to visible colors.  In that north pole image I’d say that they coded red-to-black as warm down to white as cool.  The south pole image looks like warmest is yellow-to-white, coolest is red.”

“How’d you figure that?”

“The programs fake the apparent heights.  The warmest areas are where we can see most deeply into the atmosphere, which would be at the center or edge of a vortex.  The cooler areas would be upper-level material.  The techs use that logic to generate the perspective projection that we interpret as a 3-D view.”

Vinnie’s behind us in line and getting impatient.  “I suppose there’s Science in those pretty pictures?”

“Tons of it, and a few mysteries.  JIRAM by itself is telling the researchers a lot about where and how much water and other small molecules reside in Jupiter’s atmosphere.  But Juno has eight other sensors.  Scientists expect to harvest important information from each of them.  Correlations between the data streams will give us exponentially more.”

He’s still antsy.  “Such as?”

“Like how Jupiter’s off-axis magnetic field is related to its lumpy gravitational field.  When we figure that out we’ll know a lot more about how Jupiter works, and that’ll help us understand Saturn and gas-giant exoplanets.”GRS core

Al breaks in.  “What about the mysteries, Cathleen?”

“Those storms, for instance.  They look like Earth-style hurricanes, driven by upwelling warm air.  They even go in the right direction.  But why are they crammed together so and how can they stay stable like that?  Adjacent gears have to rotate in opposite directions, but these guys all go in the same direction.  I can’t imagine what the winds between them must be like.”

“And how come there’s eight in the north pole ring but only five at the other pole?”

“Who knows, Vinnie?  The only guess I have is that Jupiter’s so big that one end doesn’t know what the other end’s doing.”

“Someone’s gonna have to do better than that.”

“Give ’em time.”

~~ Rich Olcott

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Planetary Pastry, First Course

“Morning, Al.  What’s the scone of the day?”

“No scones today, Sy.  Cathleen and one of her Astronomy students used my oven to do a whole batch of these orange-and-apricot Danishes.  Something to do with Jupiter.  Try one.”Great Apricot Spot 1
Cathleen was standing behind me.  “They’re in honor of NASA’s Juno spacecraft.  She just completed a close-up survey of Jupiter’s famous cloud formation, the Great Red Spot.  Whaddaya think?”

“Not bad.  Nice bright color and a good balance of sweetness from the apricot against tartness from the orange.”

“You noticed that, hey?  We had to do a lot of balancing — flavors, colors, the right amount of liquid.  Too juicy and the pastry part comes out gummy, too dry and you break a tooth.  Notice something else?”

“The structure, right?  Like the Spot’s collar around a mushed-up center.”

“Close, but Juno showed us that center’s anything but mushed-up.  <pulls out her smartphone>  Here’s what she sent back.”

GRS 1 @400
Credits: NASA/JPL-Caltech/SwRI/MSSS/Jason Major

“See, it’s swirls within swirls. We tried stirring the filling to look like that but it mostly smoothed out in the baking.”

“Hey, is it true what I heard that the Great Red Spot has been there for 400 years?”

“We think so, Al, but nobody knows for sure.  When Galileo published his telescopic observations of Jupiter in 1610 he didn’t mention a spot.  But that could be because he’d already caught flak from the Church by describing mountains and craters on the supposedly perfect face of the Moon.   Besides, the Jovian moons he saw were much more exciting for the science of the time.  A planet with satellites was a direct contradiction to Aristotle’s Earth-centered Solar System.”

“OK, but what about after Galileo?”

“There are records of a spot between 1665 and 1713 but then no reports of a spot for more than a century.  Maybe it was there and nobody was looking for it, maybe it had disappeared.  But Jupiter’s got one now and it’s been growing and shrinking for the past 185 years.”

“So what is it, what’s it made of and why’s it been there so long?”

“Three questions, one of them easy.”

“Which is easy, Sy?”

“The middle one.  The answer is, no-one knows what it’s made of.  That’s part of Juno‘s mission, to do close-up spectroscopy and help us wheedle what kinds of molecules are in there.  We know that Jupiter’s mostly hydrogen and helium, just like the Sun, but both of those are colorless.  Why some of the planet’s clouds are blue and some are pink — that’s a puzzle, right, Cathleen?”

“Well, we know a little more than that, especially since the Galileo probe dove 100 miles into the clouds in 1995.  The white clouds are colder and made of ammonia ice particles.  The pink clouds are warmer and … ok, we’re still working on that.”

“What about my other two questions, Cathleen?”

“People often call it a hurricane, but that’s a misnomer.  On Earth, a typical hurricane is a broad, complex ring of rainstorms with wind speeds from 75 to 200 mph.  Inside the ring wall people say it’s eerily calm.  The whole thing goes counterclockwise in the northern hemisphere, clockwise in the southern one.”

“So how’s the Great Red Spot different?”

“Size, speed, complexity, even direction.  East-to-west, the Spot is eight times wider than the biggest hurricanes.  Its collar winds run about 350 mph and it rotates counterclockwise even though it’s in Jupiter’s southern hemisphere.  It’s like a hurricane inside-out.”

“It’s not calm inside?”

“Nope, take another look at that Juno image.  There’s at least three very busy bands wrapped around a central structure that looks like it holds three distinct swirls.  That’s the part that’s easiest to understand.” GRS core

“Why so?”

“Geometry.  Adjacent segments of separate swirls have to be moving in the same direction or they’ll cancel each other out.  <scribbles diagram on a paper napkin>  Suppose I’ve got just one inside another one.  If they go in the same direction the faster one speeds up the slower one and they merge.  If they go in opposite directions, one of them disappears.  If there’s more than one inner swirl, there has to be an odd number, see?”

“So if it’s not a hurricane, what is it?”

“Got any donuts, Al?”

~~ Rich Olcott